When a new threshold breaching stall happens after a psi event was
generated and within the window duration, the new event is not
generated because the events are rate-limited to one per window. If
after that no new stall is recorded then the event will not be
generated even after rate-limiting duration has passed. This is
happening because with no new stall, window_update will not be called
even though threshold was previously breached. To fix this, record
threshold breaching occurrence and generate the event once window
duration is passed.
Suggested-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Suren Baghdasaryan <surenb@google.com>
Link: https://lore.kernel.org/r/1643093818-19835-1-git-send-email-huangzhaoyang@gmail.com
In a typical memory tiering system, there's no CPU in slow (PMEM) NUMA
nodes. But if the number of the hint page faults on a PMEM node is
the max for a task, The current NUMA balancing policy may try to place
the task on the PMEM node instead of DRAM node. This is unreasonable,
because there's no CPU in PMEM NUMA nodes. To fix this, CPU-less
nodes are ignored when searching the migration target node for a task
in this patch.
To test the patch, we run a workload that accesses more memory in PMEM
node than memory in DRAM node. Without the patch, the PMEM node will
be chosen as preferred node in task_numa_placement(). While the DRAM
node will be chosen instead with the patch.
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220214121553.582248-2-ying.huang@intel.com
The NUMA topology parameters (sched_numa_topology_type,
sched_domains_numa_levels, and sched_max_numa_distance, etc.)
identified by scheduler may be wrong for systems with CPU-less nodes.
For example, the ACPI SLIT of a system with CPU-less persistent
memory (Intel Optane DCPMM) nodes is as follows,
[000h 0000 4] Signature : "SLIT" [System Locality Information Table]
[004h 0004 4] Table Length : 0000042C
[008h 0008 1] Revision : 01
[009h 0009 1] Checksum : 59
[00Ah 0010 6] Oem ID : "XXXX"
[010h 0016 8] Oem Table ID : "XXXXXXX"
[018h 0024 4] Oem Revision : 00000001
[01Ch 0028 4] Asl Compiler ID : "INTL"
[020h 0032 4] Asl Compiler Revision : 20091013
[024h 0036 8] Localities : 0000000000000004
[02Ch 0044 4] Locality 0 : 0A 15 11 1C
[030h 0048 4] Locality 1 : 15 0A 1C 11
[034h 0052 4] Locality 2 : 11 1C 0A 1C
[038h 0056 4] Locality 3 : 1C 11 1C 0A
While the `numactl -H` output is as follows,
available: 4 nodes (0-3)
node 0 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71
node 0 size: 64136 MB
node 0 free: 5981 MB
node 1 cpus: 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95
node 1 size: 64466 MB
node 1 free: 10415 MB
node 2 cpus:
node 2 size: 253952 MB
node 2 free: 253920 MB
node 3 cpus:
node 3 size: 253952 MB
node 3 free: 253951 MB
node distances:
node 0 1 2 3
0: 10 21 17 28
1: 21 10 28 17
2: 17 28 10 28
3: 28 17 28 10
In this system, there are only 2 sockets. In each memory controller,
both DRAM and PMEM DIMMs are installed. Although the physical NUMA
topology is simple, the logical NUMA topology becomes a little
complex. Because both the distance(0, 1) and distance (1, 3) are less
than the distance (0, 3), it appears that node 1 sits between node 0
and node 3. And the whole system appears to be a glueless mesh NUMA
topology type. But it's definitely not, there is even no CPU in node 3.
This isn't a practical problem now yet. Because the PMEM nodes (node
2 and node 3 in example system) are offlined by default during system
boot. So init_numa_topology_type() called during system boot will
ignore them and set sched_numa_topology_type to NUMA_DIRECT. And
init_numa_topology_type() is only called at runtime when a CPU of a
never-onlined-before node gets plugged in. And there's no CPU in the
PMEM nodes. But it appears better to fix this to make the code more
robust.
To test the potential problem. We have used a debug patch to call
init_numa_topology_type() when the PMEM node is onlined (in
__set_migration_target_nodes()). With that, the NUMA parameters
identified by scheduler is as follows,
sched_numa_topology_type: NUMA_GLUELESS_MESH
sched_domains_numa_levels: 4
sched_max_numa_distance: 28
To fix the issue, the CPU-less nodes are ignored when the NUMA topology
parameters are identified. Because a node may become CPU-less or not
at run time because of CPU hotplug, the NUMA topology parameters need
to be re-initialized at runtime for CPU hotplug too.
With the patch, the NUMA parameters identified for the example system
above is as follows,
sched_numa_topology_type: NUMA_DIRECT
sched_domains_numa_levels: 2
sched_max_numa_distance: 21
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220214121553.582248-1-ying.huang@intel.com
In some places, kernel/sched code calls cpumask_weight() to check if
any bit of a given cpumask is set. We can do it more efficiently with
cpumask_empty() because cpumask_empty() stops traversing the cpumask as
soon as it finds first set bit, while cpumask_weight() counts all bits
unconditionally.
Signed-off-by: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220210224933.379149-23-yury.norov@gmail.com
Commit 7d2b5dd0bc ("sched/numa: Allow a floating imbalance between NUMA
nodes") allowed an imbalance between NUMA nodes such that communicating
tasks would not be pulled apart by the load balancer. This works fine when
there is a 1:1 relationship between LLC and node but can be suboptimal
for multiple LLCs if independent tasks prematurely use CPUs sharing cache.
Zen* has multiple LLCs per node with local memory channels and due to
the allowed imbalance, it's far harder to tune some workloads to run
optimally than it is on hardware that has 1 LLC per node. This patch
allows an imbalance to exist up to the point where LLCs should be balanced
between nodes.
On a Zen3 machine running STREAM parallelised with OMP to have on instance
per LLC the results and without binding, the results are
5.17.0-rc0 5.17.0-rc0
vanilla sched-numaimb-v6
MB/sec copy-16 162596.94 ( 0.00%) 580559.74 ( 257.05%)
MB/sec scale-16 136901.28 ( 0.00%) 374450.52 ( 173.52%)
MB/sec add-16 157300.70 ( 0.00%) 564113.76 ( 258.62%)
MB/sec triad-16 151446.88 ( 0.00%) 564304.24 ( 272.61%)
STREAM can use directives to force the spread if the OpenMP is new
enough but that doesn't help if an application uses threads and
it's not known in advance how many threads will be created.
Coremark is a CPU and cache intensive benchmark parallelised with
threads. When running with 1 thread per core, the vanilla kernel
allows threads to contend on cache. With the patch;
5.17.0-rc0 5.17.0-rc0
vanilla sched-numaimb-v5
Min Score-16 368239.36 ( 0.00%) 389816.06 ( 5.86%)
Hmean Score-16 388607.33 ( 0.00%) 427877.08 * 10.11%*
Max Score-16 408945.69 ( 0.00%) 481022.17 ( 17.62%)
Stddev Score-16 15247.04 ( 0.00%) 24966.82 ( -63.75%)
CoeffVar Score-16 3.92 ( 0.00%) 5.82 ( -48.48%)
It can also make a big difference for semi-realistic workloads
like specjbb which can execute arbitrary numbers of threads without
advance knowledge of how they should be placed. Even in cases where
the average performance is neutral, the results are more stable.
5.17.0-rc0 5.17.0-rc0
vanilla sched-numaimb-v6
Hmean tput-1 71631.55 ( 0.00%) 73065.57 ( 2.00%)
Hmean tput-8 582758.78 ( 0.00%) 556777.23 ( -4.46%)
Hmean tput-16 1020372.75 ( 0.00%) 1009995.26 ( -1.02%)
Hmean tput-24 1416430.67 ( 0.00%) 1398700.11 ( -1.25%)
Hmean tput-32 1687702.72 ( 0.00%) 1671357.04 ( -0.97%)
Hmean tput-40 1798094.90 ( 0.00%) 2015616.46 * 12.10%*
Hmean tput-48 1972731.77 ( 0.00%) 2333233.72 ( 18.27%)
Hmean tput-56 2386872.38 ( 0.00%) 2759483.38 ( 15.61%)
Hmean tput-64 2909475.33 ( 0.00%) 2925074.69 ( 0.54%)
Hmean tput-72 2585071.36 ( 0.00%) 2962443.97 ( 14.60%)
Hmean tput-80 2994387.24 ( 0.00%) 3015980.59 ( 0.72%)
Hmean tput-88 3061408.57 ( 0.00%) 3010296.16 ( -1.67%)
Hmean tput-96 3052394.82 ( 0.00%) 2784743.41 ( -8.77%)
Hmean tput-104 2997814.76 ( 0.00%) 2758184.50 ( -7.99%)
Hmean tput-112 2955353.29 ( 0.00%) 2859705.09 ( -3.24%)
Hmean tput-120 2889770.71 ( 0.00%) 2764478.46 ( -4.34%)
Hmean tput-128 2871713.84 ( 0.00%) 2750136.73 ( -4.23%)
Stddev tput-1 5325.93 ( 0.00%) 2002.53 ( 62.40%)
Stddev tput-8 6630.54 ( 0.00%) 10905.00 ( -64.47%)
Stddev tput-16 25608.58 ( 0.00%) 6851.16 ( 73.25%)
Stddev tput-24 12117.69 ( 0.00%) 4227.79 ( 65.11%)
Stddev tput-32 27577.16 ( 0.00%) 8761.05 ( 68.23%)
Stddev tput-40 59505.86 ( 0.00%) 2048.49 ( 96.56%)
Stddev tput-48 168330.30 ( 0.00%) 93058.08 ( 44.72%)
Stddev tput-56 219540.39 ( 0.00%) 30687.02 ( 86.02%)
Stddev tput-64 121750.35 ( 0.00%) 9617.36 ( 92.10%)
Stddev tput-72 223387.05 ( 0.00%) 34081.13 ( 84.74%)
Stddev tput-80 128198.46 ( 0.00%) 22565.19 ( 82.40%)
Stddev tput-88 136665.36 ( 0.00%) 27905.97 ( 79.58%)
Stddev tput-96 111925.81 ( 0.00%) 99615.79 ( 11.00%)
Stddev tput-104 146455.96 ( 0.00%) 28861.98 ( 80.29%)
Stddev tput-112 88740.49 ( 0.00%) 58288.23 ( 34.32%)
Stddev tput-120 186384.86 ( 0.00%) 45812.03 ( 75.42%)
Stddev tput-128 78761.09 ( 0.00%) 57418.48 ( 27.10%)
Similarly, for embarassingly parallel problems like NPB-ep, there are
improvements due to better spreading across LLC when the machine is not
fully utilised.
vanilla sched-numaimb-v6
Min ep.D 31.79 ( 0.00%) 26.11 ( 17.87%)
Amean ep.D 31.86 ( 0.00%) 26.17 * 17.86%*
Stddev ep.D 0.07 ( 0.00%) 0.05 ( 24.41%)
CoeffVar ep.D 0.22 ( 0.00%) 0.20 ( 7.97%)
Max ep.D 31.93 ( 0.00%) 26.21 ( 17.91%)
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Link: https://lore.kernel.org/r/20220208094334.16379-3-mgorman@techsingularity.net
There are inconsistencies when determining if a NUMA imbalance is allowed
that should be corrected.
o allow_numa_imbalance changes types and is not always examining
the destination group so both the type should be corrected as
well as the naming.
o find_idlest_group uses the sched_domain's weight instead of the
group weight which is different to find_busiest_group
o find_busiest_group uses the source group instead of the destination
which is different to task_numa_find_cpu
o Both find_idlest_group and find_busiest_group should account
for the number of running tasks if a move was allowed to be
consistent with task_numa_find_cpu
Fixes: 7d2b5dd0bc ("sched/numa: Allow a floating imbalance between NUMA nodes")
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Link: https://lore.kernel.org/r/20220208094334.16379-2-mgorman@techsingularity.net
Syzbot found a GPF in reweight_entity. This has been bisected to
commit 4ef0c5c6b5 ("kernel/sched: Fix sched_fork() access an invalid
sched_task_group")
There is a race between sched_post_fork() and setpriority(PRIO_PGRP)
within a thread group that causes a null-ptr-deref in
reweight_entity() in CFS. The scenario is that the main process spawns
number of new threads, which then call setpriority(PRIO_PGRP, 0, -20),
wait, and exit. For each of the new threads the copy_process() gets
invoked, which adds the new task_struct and calls sched_post_fork()
for it.
In the above scenario there is a possibility that
setpriority(PRIO_PGRP) and set_one_prio() will be called for a thread
in the group that is just being created by copy_process(), and for
which the sched_post_fork() has not been executed yet. This will
trigger a null pointer dereference in reweight_entity(), as it will
try to access the run queue pointer, which hasn't been set.
Before the mentioned change the cfs_rq pointer for the task has been
set in sched_fork(), which is called much earlier in copy_process(),
before the new task is added to the thread_group. Now it is done in
the sched_post_fork(), which is called after that. To fix the issue
the remove the update_load param from the update_load param() function
and call reweight_task() only if the task flag doesn't have the
TASK_NEW flag set.
Fixes: 4ef0c5c6b5 ("kernel/sched: Fix sched_fork() access an invalid sched_task_group")
Reported-by: syzbot+af7a719bc92395ee41b3@syzkaller.appspotmail.com
Signed-off-by: Tadeusz Struk <tadeusz.struk@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20220203161846.1160750-1-tadeusz.struk@linaro.org
The to_gov_attr_set() has been moved to the cpufreq.h, so use it to get
the gov_attr_set.
Signed-off-by: Kevin Hao <haokexin@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Rename blk_flush_plug to __blk_flush_plug and add a wrapper that includes
the NULL check instead of open coding that check everywhere.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20220127070549.1377856-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
blk_needs_flush_plug fails to account for the cb_list, which needs
flushing as well. Remove it and just check if there is a plug instead
of poking into the internals of the plug structure.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220127070549.1377856-1-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
move autogroup sysctls to autogroup.c and use the new
register_sysctl_init() to register the sysctl interface.
Signed-off-by: Zhen Ni <nizhen@uniontech.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220128095025.8745-1-nizhen@uniontech.com
set when querying membarrier(2) commands through MEMBARRIER_CMD_QUERY
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Merge tag 'sched_urgent_for_v5.17_rc2_p2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler fix from Borislav Petkov:
"Make sure the membarrier-rseq fence commands are part of the reported
set when querying membarrier(2) commands through MEMBARRIER_CMD_QUERY"
* tag 'sched_urgent_for_v5.17_rc2_p2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/membarrier: Fix membarrier-rseq fence command missing from query bitmask
When CONFIG_PROC_FS is disabled psi code generates the following
warnings:
kernel/sched/psi.c:1364:30: warning: 'psi_cpu_proc_ops' defined but not used [-Wunused-const-variable=]
1364 | static const struct proc_ops psi_cpu_proc_ops = {
| ^~~~~~~~~~~~~~~~
kernel/sched/psi.c:1355:30: warning: 'psi_memory_proc_ops' defined but not used [-Wunused-const-variable=]
1355 | static const struct proc_ops psi_memory_proc_ops = {
| ^~~~~~~~~~~~~~~~~~~
kernel/sched/psi.c:1346:30: warning: 'psi_io_proc_ops' defined but not used [-Wunused-const-variable=]
1346 | static const struct proc_ops psi_io_proc_ops = {
| ^~~~~~~~~~~~~~~
Make definitions of these structures and related functions conditional
on CONFIG_PROC_FS config.
Link: https://lkml.kernel.org/r/20220119223940.787748-3-surenb@google.com
Fixes: 0e94682b73 ("psi: introduce psi monitor")
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reported-by: kernel test robot <lkp@intel.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When CONFIG_PROC_FS is disabled psi code generates the following warnings:
kernel/sched/psi.c:1364:30: warning: 'psi_cpu_proc_ops' defined but not used [-Wunused-const-variable=]
1364 | static const struct proc_ops psi_cpu_proc_ops = {
| ^~~~~~~~~~~~~~~~
kernel/sched/psi.c:1355:30: warning: 'psi_memory_proc_ops' defined but not used [-Wunused-const-variable=]
1355 | static const struct proc_ops psi_memory_proc_ops = {
| ^~~~~~~~~~~~~~~~~~~
kernel/sched/psi.c:1346:30: warning: 'psi_io_proc_ops' defined but not used [-Wunused-const-variable=]
1346 | static const struct proc_ops psi_io_proc_ops = {
| ^~~~~~~~~~~~~~~
Make definitions of these structures and related functions conditional on
CONFIG_PROC_FS config.
Fixes: 0e94682b73 ("psi: introduce psi monitor")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220119223940.787748-3-surenb@google.com
iowait_boost signal is applied independently of util and doesn't take
into account uclamp settings of the rq. An io heavy task that is capped
by uclamp_max could still request higher frequency because
sugov_iowait_apply() doesn't clamp the boost via uclamp_rq_util_with()
like effective_cpu_util() does.
Make sure that iowait_boost honours uclamp requests by calling
uclamp_rq_util_with() when applying the boost.
Fixes: 982d9cdc22 ("sched/cpufreq, sched/uclamp: Add clamps for FAIR and RT tasks")
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20211216225320.2957053-3-qais.yousef@arm.com
sugov_update_single_{freq, perf}() contains a 'busy' filter that ensures
we don't bring the frqeuency down if there's no idle time (CPU is busy).
The problem is that with uclamp_max we will have scenarios where a busy
task is capped to run at a lower frequency and this filter prevents
applying the capping when this task starts running.
We handle this by skipping the filter when uclamp is enabled and the rq
is being capped by uclamp_max.
We introduce a new function uclamp_rq_is_capped() to help detecting when
this capping is taking effect. Some code shuffling was required to allow
using cpu_util_{cfs, rt}() in this new function.
On 2 Core SMT2 Intel laptop I see:
Without this patch:
uclampset -M 0 sysbench --test=cpu --threads = 4 run
produces a score of ~3200 consistently. Which is the highest possible.
Compiling the kernel also results in frequency running at max 3.1GHz all
the time - running uclampset -M 400 to cap it has no effect without this
patch.
With this patch:
uclampset -M 0 sysbench --test=cpu --threads = 4 run
produces a score of ~1100 with some outliers in ~1700. Uclamp max
aggregates the performance requirements, so having high values sometimes
is expected if some other task happens to require that frequency starts
running at the same time.
When compiling the kernel with uclampset -M 400 I can see the
frequencies mostly in the ~2GHz region. Helpful to conserve power and
prevent heating when not plugged in.
Fixes: 982d9cdc22 ("sched/cpufreq, sched/uclamp: Add clamps for FAIR and RT tasks")
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211216225320.2957053-2-qais.yousef@arm.com
We can't use this tracepoint in modules without having the symbol
exported first, fix that.
Fixes: 765047932f ("sched/pelt: Add support to track thermal pressure")
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211028115005.873539-1-qais.yousef@arm.com
The child processes will inherit numa_pages_migrated and
total_numa_faults from the parent. It means even if there is no numa
fault happen on the child, the statistics in /proc/$pid of the child
process might show huge amount. This is a bit weird. Let's initialize
them when do fork.
Signed-off-by: Honglei Wang <wanghonglei@didichuxing.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lore.kernel.org/r/20220113133920.49900-1-wanghonglei@didichuxing.com
The older format of /proc/pid/sched printed home node info which
required the mempolicy and task lock around mpol_get(). However
the format has changed since then and there is no need for
sched_show_numa() any more to have mempolicy argument,
asssociated mpol_get/put and task_lock/unlock. Remove them.
Fixes: 397f2378f1 ("sched/numa: Fix numa balancing stats in /proc/pid/sched")
Signed-off-by: Bharata B Rao <bharata@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lore.kernel.org/r/20220118050515.2973-1-bharata@amd.com
The membarrier command MEMBARRIER_CMD_QUERY allows querying the
available membarrier commands. When the membarrier-rseq fence commands
were added, a new MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ_BITMASK was
introduced with the intent to expose them with the MEMBARRIER_CMD_QUERY
command, the but it was never added to MEMBARRIER_CMD_BITMASK.
The membarrier-rseq fence commands are therefore not wired up with the
query command.
Rename MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ_BITMASK to
MEMBARRIER_PRIVATE_EXPEDITED_RSEQ_BITMASK (the bitmask is not a command
per-se), and change the erroneous
MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_RSEQ_BITMASK (which does not
actually exist) to MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_RSEQ.
Wire up MEMBARRIER_PRIVATE_EXPEDITED_RSEQ_BITMASK in
MEMBARRIER_CMD_BITMASK. Fixing this allows discovering availability of
the membarrier-rseq fence feature.
Fixes: 2a36ab717e ("rseq/membarrier: Add MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ")
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@vger.kernel.org> # 5.10+
Link: https://lkml.kernel.org/r/20220117203010.30129-1-mathieu.desnoyers@efficios.com
propagation in the sched hierarchies and other minor cleanups and
improvements
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Merge tag 'sched_urgent_for_v5.17_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler fixes from Borislav Petkov:
"A bunch of fixes: forced idle time accounting, utilization values
propagation in the sched hierarchies and other minor cleanups and
improvements"
* tag 'sched_urgent_for_v5.17_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
kernel/sched: Remove dl_boosted flag comment
sched: Avoid double preemption in __cond_resched_*lock*()
sched/fair: Fix all kernel-doc warnings
sched/core: Accounting forceidle time for all tasks except idle task
sched/pelt: Relax the sync of load_sum with load_avg
sched/pelt: Relax the sync of runnable_sum with runnable_avg
sched/pelt: Continue to relax the sync of util_sum with util_avg
sched/pelt: Relax the sync of util_sum with util_avg
psi: Fix uaf issue when psi trigger is destroyed while being polled
For PREEMPT/DYNAMIC_PREEMPT the *_unlock() will already trigger a
preemption, no point in then calling preempt_schedule_common()
*again*.
Use _cond_resched() instead, since this is a NOP for the preemptible
configs while it provide a preemption point for the others.
Reported-by: xuhaifeng <xuhaifeng@oppo.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/YcGnvDEYBwOiV0cR@hirez.programming.kicks-ass.net
Quieten all kernel-doc warnings in kernel/sched/fair.c:
kernel/sched/fair.c:3663: warning: No description found for return value of 'update_cfs_rq_load_avg'
kernel/sched/fair.c:8601: warning: No description found for return value of 'asym_smt_can_pull_tasks'
kernel/sched/fair.c:8673: warning: Function parameter or member 'sds' not described in 'update_sg_lb_stats'
kernel/sched/fair.c:9483: warning: contents before sections
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Acked-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20211218055900.2704-1-rdunlap@infradead.org
There are two types of forced idle time: forced idle time from cookie'd
task and forced idle time form uncookie'd task. The forced idle time from
uncookie'd task is actually caused by the cookie'd task in runqueue
indirectly, and it's more accurate to measure the capacity loss with the
sum of both.
Assuming cpu x and cpu y are a pair of SMT siblings, consider the
following scenarios:
1.There's a cookie'd task running on cpu x, and there're 4 uncookie'd
tasks running on cpu y. For cpu x, there will be 80% forced idle time
(from uncookie'd task); for cpu y, there will be 20% forced idle time
(from cookie'd task).
2.There's a uncookie'd task running on cpu x, and there're 4 cookie'd
tasks running on cpu y. For cpu x, there will be 80% forced idle time
(from cookie'd task); for cpu y, there will be 20% forced idle time
(from uncookie'd task).
The scenario1 can recurrent by stress-ng(scenario2 can recurrent similary):
(cookie'd)taskset -c x stress-ng -c 1 -l 100
(uncookie'd)taskset -c y stress-ng -c 4 -l 100
In the above two scenarios, the total capacity loss is 1 cpu, but in
scenario1, the cookie'd forced idle time tells us 20% cpu capacity loss, in
scenario2, the cookie'd forced idle time tells us 80% cpu capacity loss,
which are not accurate. It'll be more accurate to measure with cookie'd
forced idle time and uncookie'd forced idle time.
Signed-off-by: Cruz Zhao <CruzZhao@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Josh Don <joshdon@google.com>
Link: https://lore.kernel.org/r/1641894961-9241-2-git-send-email-CruzZhao@linux.alibaba.com
Similarly to util_avg and util_sum, don't sync load_sum with the low
bound of load_avg but only ensure that load_sum stays in the correct range.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Sachin Sant <sachinp@linux.ibm.com>
Link: https://lkml.kernel.org/r/20220111134659.24961-5-vincent.guittot@linaro.org
Similarly to util_avg and util_sum, don't sync runnable_sum with the low
bound of runnable_avg but only ensure that runnable_sum stays in the
correct range.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Sachin Sant <sachinp@linux.ibm.com>
Link: https://lkml.kernel.org/r/20220111134659.24961-4-vincent.guittot@linaro.org
Rick reported performance regressions in bugzilla because of cpu frequency
being lower than before:
https://bugzilla.kernel.org/show_bug.cgi?id=215045
He bisected the problem to:
commit 1c35b07e6d ("sched/fair: Ensure _sum and _avg values stay consistent")
This commit forces util_sum to be synced with the new util_avg after
removing the contribution of a task and before the next periodic sync. By
doing so util_sum is rounded to its lower bound and might lost up to
LOAD_AVG_MAX-1 of accumulated contribution which has not yet been
reflected in util_avg.
update_tg_cfs_util() is not the only place where we round util_sum and
lost some accumulated contributions that are not already reflected in
util_avg. Modify update_tg_cfs_util() and detach_entity_load_avg() to not
sync util_sum with the new util_avg. Instead of always setting util_sum to
the low bound of util_avg, which can significantly lower the utilization,
we propagate the difference. In addition, we also check that cfs's util_sum
always stays above the lower bound for a given util_avg as it has been
observed that sched_entity's util_sum is sometimes above cfs one.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Sachin Sant <sachinp@linux.ibm.com>
Link: https://lkml.kernel.org/r/20220111134659.24961-3-vincent.guittot@linaro.org
Rick reported performance regressions in bugzilla because of cpu frequency
being lower than before:
https://bugzilla.kernel.org/show_bug.cgi?id=215045
He bisected the problem to:
commit 1c35b07e6d ("sched/fair: Ensure _sum and _avg values stay consistent")
This commit forces util_sum to be synced with the new util_avg after
removing the contribution of a task and before the next periodic sync. By
doing so util_sum is rounded to its lower bound and might lost up to
LOAD_AVG_MAX-1 of accumulated contribution which has not yet been
reflected in util_avg.
Instead of always setting util_sum to the low bound of util_avg, which can
significantly lower the utilization of root cfs_rq after propagating the
change down into the hierarchy, we revert the change of util_sum and
propagate the difference.
In addition, we also check that cfs's util_sum always stays above the
lower bound for a given util_avg as it has been observed that
sched_entity's util_sum is sometimes above cfs one.
Fixes: 1c35b07e6d ("sched/fair: Ensure _sum and _avg values stay consistent")
Reported-by: Rick Yiu <rickyiu@google.com>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Sachin Sant <sachinp@linux.ibm.com>
Link: https://lkml.kernel.org/r/20220111134659.24961-2-vincent.guittot@linaro.org
With write operation on psi files replacing old trigger with a new one,
the lifetime of its waitqueue is totally arbitrary. Overwriting an
existing trigger causes its waitqueue to be freed and pending poll()
will stumble on trigger->event_wait which was destroyed.
Fix this by disallowing to redefine an existing psi trigger. If a write
operation is used on a file descriptor with an already existing psi
trigger, the operation will fail with EBUSY error.
Also bypass a check for psi_disabled in the psi_trigger_destroy as the
flag can be flipped after the trigger is created, leading to a memory
leak.
Fixes: 0e94682b73 ("psi: introduce psi monitor")
Reported-by: syzbot+cdb5dd11c97cc532efad@syzkaller.appspotmail.com
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Analyzed-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20220111232309.1786347-1-surenb@google.com
Pull signal/exit/ptrace updates from Eric Biederman:
"This set of changes deletes some dead code, makes a lot of cleanups
which hopefully make the code easier to follow, and fixes bugs found
along the way.
The end-game which I have not yet reached yet is for fatal signals
that generate coredumps to be short-circuit deliverable from
complete_signal, for force_siginfo_to_task not to require changing
userspace configured signal delivery state, and for the ptrace stops
to always happen in locations where we can guarantee on all
architectures that the all of the registers are saved and available on
the stack.
Removal of profile_task_ext, profile_munmap, and profile_handoff_task
are the big successes for dead code removal this round.
A bunch of small bug fixes are included, as most of the issues
reported were small enough that they would not affect bisection so I
simply added the fixes and did not fold the fixes into the changes
they were fixing.
There was a bug that broke coredumps piped to systemd-coredump. I
dropped the change that caused that bug and replaced it entirely with
something much more restrained. Unfortunately that required some
rebasing.
Some successes after this set of changes: There are few enough calls
to do_exit to audit in a reasonable amount of time. The lifetime of
struct kthread now matches the lifetime of struct task, and the
pointer to struct kthread is no longer stored in set_child_tid. The
flag SIGNAL_GROUP_COREDUMP is removed. The field group_exit_task is
removed. Issues where task->exit_code was examined with
signal->group_exit_code should been examined were fixed.
There are several loosely related changes included because I am
cleaning up and if I don't include them they will probably get lost.
The original postings of these changes can be found at:
https://lkml.kernel.org/r/87a6ha4zsd.fsf@email.froward.int.ebiederm.orghttps://lkml.kernel.org/r/87bl1kunjj.fsf@email.froward.int.ebiederm.orghttps://lkml.kernel.org/r/87r19opkx1.fsf_-_@email.froward.int.ebiederm.org
I trimmed back the last set of changes to only the obviously correct
once. Simply because there was less time for review than I had hoped"
* 'signal-for-v5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (44 commits)
ptrace/m68k: Stop open coding ptrace_report_syscall
ptrace: Remove unused regs argument from ptrace_report_syscall
ptrace: Remove second setting of PT_SEIZED in ptrace_attach
taskstats: Cleanup the use of task->exit_code
exit: Use the correct exit_code in /proc/<pid>/stat
exit: Fix the exit_code for wait_task_zombie
exit: Coredumps reach do_group_exit
exit: Remove profile_handoff_task
exit: Remove profile_task_exit & profile_munmap
signal: clean up kernel-doc comments
signal: Remove the helper signal_group_exit
signal: Rename group_exit_task group_exec_task
coredump: Stop setting signal->group_exit_task
signal: Remove SIGNAL_GROUP_COREDUMP
signal: During coredumps set SIGNAL_GROUP_EXIT in zap_process
signal: Make coredump handling explicit in complete_signal
signal: Have prepare_signal detect coredumps using signal->core_state
signal: Have the oom killer detect coredumps using signal->core_state
exit: Move force_uaccess back into do_exit
exit: Guarantee make_task_dead leaks the tsk when calling do_task_exit
...
"Lots of cleanups and preparation; highlights:
- futex: Cleanup and remove runtime futex_cmpxchg detection
- rtmutex: Some fixes for the PREEMPT_RT locking infrastructure
- kcsan: Share owner_on_cpu() between mutex,rtmutex and rwsem and
annotate the racy owner->on_cpu access *once*.
- atomic64: Dead-Code-Elemination"
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Merge tag 'locking_core_for_v5.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking updates from Borislav Petkov:
"Lots of cleanups and preparation. Highlights:
- futex: Cleanup and remove runtime futex_cmpxchg detection
- rtmutex: Some fixes for the PREEMPT_RT locking infrastructure
- kcsan: Share owner_on_cpu() between mutex,rtmutex and rwsem and
annotate the racy owner->on_cpu access *once*.
- atomic64: Dead-Code-Elemination"
[ Description above by Peter Zijlstra ]
* tag 'locking_core_for_v5.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
locking/atomic: atomic64: Remove unusable atomic ops
futex: Fix additional regressions
locking: Allow to include asm/spinlock_types.h from linux/spinlock_types_raw.h
x86/mm: Include spinlock_t definition in pgtable.
locking: Mark racy reads of owner->on_cpu
locking: Make owner_on_cpu() into <linux/sched.h>
lockdep/selftests: Adapt ww-tests for PREEMPT_RT
lockdep/selftests: Skip the softirq related tests on PREEMPT_RT
lockdep/selftests: Unbalanced migrate_disable() & rcu_read_lock().
lockdep/selftests: Avoid using local_lock_{acquire|release}().
lockdep: Remove softirq accounting on PREEMPT_RT.
locking/rtmutex: Add rt_mutex_lock_nest_lock() and rt_mutex_lock_killable().
locking/rtmutex: Squash self-deadlock check for ww_rt_mutex.
locking: Remove rt_rwlock_is_contended().
sched: Trigger warning if ->migration_disabled counter underflows.
futex: Fix sparc32/m68k/nds32 build regression
futex: Remove futex_cmpxchg detection
futex: Ensure futex_atomic_cmpxchg_inatomic() is present
kernel/locking: Use a pointer in ww_mutex_trylock().
"Mostly minor things this time; some highlights:
- core-sched: Add 'Forced Idle' accounting; this allows to track how
much CPU time is 'lost' due to core scheduling constraints.
- psi: Fix for MEM_FULL; a task running reclaim would be counted as a
runnable task and prevent MEM_FULL from being reported.
- cpuacct: Long standing fixes for some cgroup accounting issues.
- rt: Bandwidth timer could, under unusual circumstances, be failed to
armed, leading to indefinite throttling."
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Merge tag 'sched_core_for_v5.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Borislav Petkov:
"Mostly minor things this time; some highlights:
- core-sched: Add 'Forced Idle' accounting; this allows to track how
much CPU time is 'lost' due to core scheduling constraints.
- psi: Fix for MEM_FULL; a task running reclaim would be counted as a
runnable task and prevent MEM_FULL from being reported.
- cpuacct: Long standing fixes for some cgroup accounting issues.
- rt: Bandwidth timer could, under unusual circumstances, be failed
to armed, leading to indefinite throttling."
[ Description above by Peter Zijlstra ]
* tag 'sched_core_for_v5.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/fair: Replace CFS internal cpu_util() with cpu_util_cfs()
sched/fair: Cleanup task_util and capacity type
sched/rt: Try to restart rt period timer when rt runtime exceeded
sched/fair: Document the slow path and fast path in select_task_rq_fair
sched/fair: Fix per-CPU kthread and wakee stacking for asym CPU capacity
sched/fair: Fix detection of per-CPU kthreads waking a task
sched/cpuacct: Make user/system times in cpuacct.stat more precise
sched/cpuacct: Fix user/system in shown cpuacct.usage*
cpuacct: Convert BUG_ON() to WARN_ON_ONCE()
cputime, cpuacct: Include guest time in user time in cpuacct.stat
psi: Fix PSI_MEM_FULL state when tasks are in memstall and doing reclaim
sched/core: Forced idle accounting
psi: Add a missing SPDX license header
psi: Remove repeated verbose comment
This series provides KCSAN fixes and also the ability to take memory
barriers into account for weakly-ordered systems. This last can increase
the probability of detecting certain types of data races.
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Merge tag 'kcsan.2022.01.09a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu
Pull KCSAN updates from Paul McKenney:
"This provides KCSAN fixes and also the ability to take memory barriers
into account for weakly-ordered systems. This last can increase the
probability of detecting certain types of data races"
* tag 'kcsan.2022.01.09a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu: (29 commits)
kcsan: Only test clear_bit_unlock_is_negative_byte if arch defines it
kcsan: Avoid nested contexts reading inconsistent reorder_access
kcsan: Turn barrier instrumentation into macros
kcsan: Make barrier tests compatible with lockdep
kcsan: Support WEAK_MEMORY with Clang where no objtool support exists
compiler_attributes.h: Add __disable_sanitizer_instrumentation
objtool, kcsan: Remove memory barrier instrumentation from noinstr
objtool, kcsan: Add memory barrier instrumentation to whitelist
sched, kcsan: Enable memory barrier instrumentation
mm, kcsan: Enable barrier instrumentation
x86/qspinlock, kcsan: Instrument barrier of pv_queued_spin_unlock()
x86/barriers, kcsan: Use generic instrumentation for non-smp barriers
asm-generic/bitops, kcsan: Add instrumentation for barriers
locking/atomics, kcsan: Add instrumentation for barriers
locking/barriers, kcsan: Support generic instrumentation
locking/barriers, kcsan: Add instrumentation for barriers
kcsan: selftest: Add test case to check memory barrier instrumentation
kcsan: Ignore GCC 11+ warnings about TSan runtime support
kcsan: test: Add test cases for memory barrier instrumentation
kcsan: test: Match reordered or normal accesses
...
accesing it in order to prevent any potential data races, and convert
all users to those new accessors
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Merge tag 'core_entry_for_v5.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull thread_info flag accessor helper updates from Borislav Petkov:
"Add a set of thread_info.flags accessors which snapshot it before
accesing it in order to prevent any potential data races, and convert
all users to those new accessors"
* tag 'core_entry_for_v5.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
powerpc: Snapshot thread flags
powerpc: Avoid discarding flags in system_call_exception()
openrisc: Snapshot thread flags
microblaze: Snapshot thread flags
arm64: Snapshot thread flags
ARM: Snapshot thread flags
alpha: Snapshot thread flags
sched: Snapshot thread flags
entry: Snapshot thread flags
x86: Snapshot thread flags
thread_info: Add helpers to snapshot thread flags
The point of using set_child_tid to hold the kthread pointer was that
it already did what is necessary. There are now restrictions on when
set_child_tid can be initialized and when set_child_tid can be used in
schedule_tail. Which indicates that continuing to use set_child_tid
to hold the kthread pointer is a bad idea.
Instead of continuing to use the set_child_tid field of task_struct
generalize the pf_io_worker field of task_struct and use it to hold
the kthread pointer.
Rename pf_io_worker (which is a void * pointer) to worker_private so
it can be used to store kthreads struct kthread pointer. Update the
kthread code to store the kthread pointer in the worker_private field.
Remove the places where set_child_tid had to be dealt with carefully
because kthreads also used it.
Link: https://lkml.kernel.org/r/CAHk-=wgtFAA9SbVYg0gR1tqPMC17-NYcs0GQkaYg1bGhh1uJQQ@mail.gmail.com
Link: https://lkml.kernel.org/r/87a6grvqy8.fsf_-_@email.froward.int.ebiederm.org
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Kernel threads abuse set_child_tid. Historically that has been fine
as set_child_tid was initialized after the kernel thread had been
forked. Unfortunately storing struct kthread in set_child_tid after
the thread is running makes struct kthread being unusable for storing
result codes of the thread.
When set_child_tid is set to struct kthread during fork that results
in schedule_tail writing the thread id to the beggining of struct
kthread (if put_user does not realize it is a kernel address).
Solve this by skipping the put_user for all kthreads.
Reported-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lkml.kernel.org/r/YcNsG0Lp94V13whH@archlinux-ax161
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Today the rules are a bit iffy and arbitrary about which kernel
threads have struct kthread present. Both idle threads and thread
started with create_kthread want struct kthread present so that is
effectively all kernel threads. Make the rule that if PF_KTHREAD
and the task is running then struct kthread is present.
This will allow the kernel thread code to using tsk->exit_code
with different semantics from ordinary processes.
To make ensure that struct kthread is present for all
kernel threads move it's allocation into copy_process.
Add a deallocation of struct kthread in exec for processes
that were kernel threads.
Move the allocation of struct kthread for the initial thread
earlier so that it is not repeated for each additional idle
thread.
Move the initialization of struct kthread into set_kthread_struct
so that the structure is always and reliably initailized.
Clear set_child_tid in free_kthread_struct to ensure the kthread
struct is reliably freed during exec. The function
free_kthread_struct does not need to clear vfork_done during exec as
exec_mm_release called from exec_mmap has already cleared vfork_done.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
cpu_util_cfs() was created by commit d4edd662ac ("sched/cpufreq: Use
the DEADLINE utilization signal") to enable the access to CPU
utilization from the Schedutil CPUfreq governor.
Commit a07630b8b2 ("sched/cpufreq/schedutil: Use util_est for OPP
selection") added util_est support later.
The only thing cpu_util() is doing on top of what cpu_util_cfs() already
does is to clamp the return value to the [0..capacity_orig] capacity
range of the CPU. Integrating this into cpu_util_cfs() is not harming
the existing users (Schedutil and CPUfreq cooling (latter via
sched_cpu_util() wrapper)).
For straightforwardness, prefer to keep using `int cpu` as the function
parameter over using `struct rq *rq` which might avoid some calls to
cpu_rq(cpu) -> per_cpu(runqueues, cpu) -> RELOC_HIDE().
Update cfs_util()'s documentation and reuse it for cpu_util_cfs().
Remove cpu_util().
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20211118164240.623551-1-dietmar.eggemann@arm.com
There's no fundamental reason to disable KCSAN for scheduler code,
except for excessive noise and performance concerns (instrumenting
scheduler code is usually a good way to stress test KCSAN itself).
However, several core sched functions imply memory barriers that are
invisible to KCSAN without instrumentation, but are required to avoid
false positives. Therefore, unconditionally enable instrumentation of
memory barriers in scheduler code. Also update the comment to reflect
this and be a bit more brief.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Several ->poll() implementations are special in that they use a
waitqueue whose lifetime is the current task, rather than the struct
file as is normally the case. This is okay for blocking polls, since a
blocking poll occurs within one task; however, non-blocking polls
require another solution. This solution is for the queue to be cleared
before it is freed, using 'wake_up_poll(wq, EPOLLHUP | POLLFREE);'.
However, that has a bug: wake_up_poll() calls __wake_up() with
nr_exclusive=1. Therefore, if there are multiple "exclusive" waiters,
and the wakeup function for the first one returns a positive value, only
that one will be called. That's *not* what's needed for POLLFREE;
POLLFREE is special in that it really needs to wake up everyone.
Considering the three non-blocking poll systems:
- io_uring poll doesn't handle POLLFREE at all, so it is broken anyway.
- aio poll is unaffected, since it doesn't support exclusive waits.
However, that's fragile, as someone could add this feature later.
- epoll doesn't appear to be broken by this, since its wakeup function
returns 0 when it sees POLLFREE. But this is fragile.
Although there is a workaround (see epoll), it's better to define a
function which always sends POLLFREE to all waiters. Add such a
function. Also make it verify that the queue really becomes empty after
all waiters have been woken up.
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20211209010455.42744-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
task_util and capacity are comparable unsigned long values. There is no
need for an intermidiate implicit signed cast.
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211207095755.859972-1-vincent.donnefort@arm.com
When rt_runtime is modified from -1 to a valid control value, it may
cause the task to be throttled all the time. Operations like the following
will trigger the bug. E.g:
1. echo -1 > /proc/sys/kernel/sched_rt_runtime_us
2. Run a FIFO task named A that executes while(1)
3. echo 950000 > /proc/sys/kernel/sched_rt_runtime_us
When rt_runtime is -1, The rt period timer will not be activated when task
A enqueued. And then the task will be throttled after setting rt_runtime to
950,000. The task will always be throttled because the rt period timer is
not activated.
Fixes: d0b27fa778 ("sched: rt-group: synchonised bandwidth period")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Li Hua <hucool.lihua@huawei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211203033618.11895-1-hucool.lihua@huawei.com
All People I know including myself took a long time to figure out that
typical wakeup will always go to fast path and never go to slow path
except WF_FORK and WF_EXEC.
Vincent reminded me once in a linaro meeting and made me understand
slow path won't happen for WF_TTWU. But my other friends repeatedly
wasted a lot of time on testing this path like me before I reminded
them.
So obviously the code needs some document.
Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211016111109.5559-1-21cnbao@gmail.com
If migrate_enable() is used more often than its counter part then it
remains undetected and rq::nr_pinned will underflow, too.
Add a warning if migrate_enable() is attempted if without a matching a
migrate_disable().
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20211129174654.668506-2-bigeasy@linutronix.de
select_idle_sibling() has a special case for tasks woken up by a per-CPU
kthread where the selected CPU is the previous one. For asymmetric CPU
capacity systems, the assumption was that the wakee couldn't have a
bigger utilization during task placement than it used to have during the
last activation. That was not considering uclamp.min which can completely
change between two task activations and as a consequence mandates the
fitness criterion asym_fits_capacity(), even for the exit path described
above.
Fixes: b4c9c9f156 ("sched/fair: Prefer prev cpu in asymmetric wakeup path")
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lkml.kernel.org/r/20211129173115.4006346-1-vincent.donnefort@arm.com
select_idle_sibling() has a special case for tasks woken up by a per-CPU
kthread, where the selected CPU is the previous one. However, the current
condition for this exit path is incomplete. A task can wake up from an
interrupt context (e.g. hrtimer), while a per-CPU kthread is running. A
such scenario would spuriously trigger the special case described above.
Also, a recent change made the idle task like a regular per-CPU kthread,
hence making that situation more likely to happen
(is_per_cpu_kthread(swapper) being true now).
Checking for task context makes sure select_idle_sibling() will not
interpret a wake up from any other context as a wake up by a per-CPU
kthread.
Fixes: 52262ee567 ("sched/fair: Allow a per-CPU kthread waking a task to stack on the same CPU, to fix XFS performance regression")
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lore.kernel.org/r/20211201143450.479472-1-vincent.donnefort@arm.com
Commit d81ae8aac8 ("sched/uclamp: Fix initialization of struct
uclamp_rq") introduced a bug where uclamp_max of the rq is not reset to
match the woken up task's uclamp_max when the rq is idle.
The code was relying on rq->uclamp_max initialized to zero, so on first
enqueue
static inline void uclamp_rq_inc_id(struct rq *rq, struct task_struct *p,
enum uclamp_id clamp_id)
{
...
if (uc_se->value > READ_ONCE(uc_rq->value))
WRITE_ONCE(uc_rq->value, uc_se->value);
}
was actually resetting it. But since commit d81ae8aac8 changed the
default to 1024, this no longer works. And since rq->uclamp_flags is
also initialized to 0, neither above code path nor uclamp_idle_reset()
update the rq->uclamp_max on first wake up from idle.
This is only visible from first wake up(s) until the first dequeue to
idle after enabling the static key. And it only matters if the
uclamp_max of this task is < 1024 since only then its uclamp_max will be
effectively ignored.
Fix it by properly initializing rq->uclamp_flags = UCLAMP_FLAG_IDLE to
ensure uclamp_idle_reset() is called which then will update the rq
uclamp_max value as expected.
Fixes: d81ae8aac8 ("sched/uclamp: Fix initialization of struct uclamp_rq")
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <Valentin.Schneider@arm.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lkml.kernel.org/r/20211202112033.1705279-1-qais.yousef@arm.com
__setup() callbacks expect 1 for success and 0 for failure. Correct the
usage here to reflect that.
Fixes: 826bfeb37b ("preempt/dynamic: Support dynamic preempt with preempt= boot option")
Reported-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrew Halaney <ahalaney@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211203233203.133581-1-ahalaney@redhat.com
getrusage(RUSAGE_THREAD) with nohz_full may return shorter utime/stime
than the actual time.
task_cputime_adjusted() snapshots utime and stime and then adjust their
sum to match the scheduler maintained cputime.sum_exec_runtime.
Unfortunately in nohz_full, sum_exec_runtime is only updated once per
second in the worst case, causing a discrepancy against utime and stime
that can be updated anytime by the reader using vtime.
To fix this situation, perform an update of cputime.sum_exec_runtime
when the cputime snapshot reports the task as actually running while
the tick is disabled. The related overhead is then contained within the
relevant situations.
Reported-by: Hasegawa Hitomi <hasegawa-hitomi@fujitsu.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Hasegawa Hitomi <hasegawa-hitomi@fujitsu.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Acked-by: Phil Auld <pauld@redhat.com>
Link: https://lore.kernel.org/r/20211026141055.57358-3-frederic@kernel.org
Some thread flags can be set remotely, and so even when IRQs are disabled,
the flags can change under our feet. Generally this is unlikely to cause a
problem in practice, but it is somewhat unsound, and KCSAN will
legitimately warn that there is a data race.
To avoid such issues, a snapshot of the flags has to be taken prior to
using them. Some places already use READ_ONCE() for that, others do not.
Convert them all to the new flag accessor helpers.
The READ_ONCE(ti->flags) .. cmpxchg(ti->flags) loop in
set_nr_if_polling() is left as-is for clarity.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20211129130653.2037928-4-mark.rutland@arm.com
To hot unplug a CPU, the idle task on that CPU calls a few layers of C
code before finally leaving the kernel. When KASAN is in use, poisoned
shadow is left around for each of the active stack frames, and when
shadow call stacks are in use. When shadow call stacks (SCS) are in use
the task's saved SCS SP is left pointing at an arbitrary point within
the task's shadow call stack.
When a CPU is offlined than onlined back into the kernel, this stale
state can adversely affect execution. Stale KASAN shadow can alias new
stackframes and result in bogus KASAN warnings. A stale SCS SP is
effectively a memory leak, and prevents a portion of the shadow call
stack being used. Across a number of hotplug cycles the idle task's
entire shadow call stack can become unusable.
We previously fixed the KASAN issue in commit:
e1b77c9298 ("sched/kasan: remove stale KASAN poison after hotplug")
... by removing any stale KASAN stack poison immediately prior to
onlining a CPU.
Subsequently in commit:
f1a0a376ca ("sched/core: Initialize the idle task with preemption disabled")
... the refactoring left the KASAN and SCS cleanup in one-time idle
thread initialization code rather than something invoked prior to each
CPU being onlined, breaking both as above.
We fixed SCS (but not KASAN) in commit:
63acd42c0d ("sched/scs: Reset the shadow stack when idle_task_exit")
... but as this runs in the context of the idle task being offlined it's
potentially fragile.
To fix these consistently and more robustly, reset the SCS SP and KASAN
shadow of a CPU's idle task immediately before we online that CPU in
bringup_cpu(). This ensures the idle task always has a consistent state
when it is running, and removes the need to so so when exiting an idle
task.
Whenever any thread is created, dup_task_struct() will give the task a
stack which is free of KASAN shadow, and initialize the task's SCS SP,
so there's no need to specially initialize either for idle thread within
init_idle(), as this was only necessary to handle hotplug cycles.
I've tested this on arm64 with:
* gcc 11.1.0, defconfig +KASAN_INLINE, KASAN_STACK
* clang 12.0.0, defconfig +KASAN_INLINE, KASAN_STACK, SHADOW_CALL_STACK
... offlining and onlining CPUS with:
| while true; do
| for C in /sys/devices/system/cpu/cpu*/online; do
| echo 0 > $C;
| echo 1 > $C;
| done
| done
Fixes: f1a0a376ca ("sched/core: Initialize the idle task with preemption disabled")
Reported-by: Qian Cai <quic_qiancai@quicinc.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Tested-by: Qian Cai <quic_qiancai@quicinc.com>
Link: https://lore.kernel.org/lkml/20211115113310.35693-1-mark.rutland@arm.com/
cpuacct.stat shows user time based on raw random precision tick
based counters. Use cputime_addjust() to scale these values against the
total runtime accounted by the scheduler, like we already do
for user/system times in /proc/<pid>/stat.
Signed-off-by: Andrey Ryabinin <arbn@yandex-team.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20211115164607.23784-4-arbn@yandex-team.com
cpuacct has 2 different ways of accounting and showing user
and system times.
The first one uses cpuacct_account_field() to account times
and cpuacct.stat file to expose them. And this one seems to work ok.
The second one is uses cpuacct_charge() function for accounting and
set of cpuacct.usage* files to show times. Despite some attempts to
fix it in the past it still doesn't work. Sometimes while running KVM
guest the cpuacct_charge() accounts most of the guest time as
system time. This doesn't match with user&system times shown in
cpuacct.stat or proc/<pid>/stat.
Demonstration:
# git clone https://github.com/aryabinin/kvmsample
# make
# mkdir /sys/fs/cgroup/cpuacct/test
# echo $$ > /sys/fs/cgroup/cpuacct/test/tasks
# ./kvmsample &
# for i in {1..5}; do cat /sys/fs/cgroup/cpuacct/test/cpuacct.usage_sys; sleep 1; done
1976535645
2979839428
3979832704
4983603153
5983604157
Use cpustats accounted in cpuacct_account_field() as the source
of user/sys times for cpuacct.usage* files. Make cpuacct_charge()
to account only summary execution time.
Fixes: d740037fac ("sched/cpuacct: Split usage accounting into user_usage and sys_usage")
Signed-off-by: Andrey Ryabinin <arbn@yandex-team.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20211115164607.23784-3-arbn@yandex-team.com
Replace fatal BUG_ON() with more safe WARN_ON_ONCE() in cpuacct_cpuusage_read().
Signed-off-by: Andrey Ryabinin <arbn@yandex-team.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20211115164607.23784-2-arbn@yandex-team.com
cpuacct.stat in no-root cgroups shows user time without guest time
included int it. This doesn't match with user time shown in root
cpuacct.stat and /proc/<pid>/stat. This also affects cgroup2's cpu.stat
in the same way.
Make account_guest_time() to add user time to cgroup's cpustat to
fix this.
Fixes: ef12fefabf ("cpuacct: add per-cgroup utime/stime statistics")
Signed-off-by: Andrey Ryabinin <arbn@yandex-team.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20211115164607.23784-1-arbn@yandex-team.com
We've noticed cases where tasks in a cgroup are stalled on memory but
there is little memory FULL pressure since tasks stay on the runqueue
in reclaim.
A simple example involves a single threaded program that keeps leaking
and touching large amounts of memory. It runs in a cgroup with swap
enabled, memory.high set at 10M and cpu.max ratio set at 5%. Though
there is significant CPU pressure and memory SOME, there is barely any
memory FULL since the task enters reclaim and stays on the runqueue.
However, this memory-bound task is effectively stalled on memory and
we expect memory FULL to match memory SOME in this scenario.
The code is confused about memstall && running, thinking there is a
stalled task and a productive task when there's only one task: a
reclaimer that's counted as both. To fix this, we redefine the
condition for PSI_MEM_FULL to check that all running tasks are in an
active memstall instead of checking that there are no running tasks.
case PSI_MEM_FULL:
- return unlikely(tasks[NR_MEMSTALL] && !tasks[NR_RUNNING]);
+ return unlikely(tasks[NR_MEMSTALL] &&
+ tasks[NR_RUNNING] == tasks[NR_MEMSTALL_RUNNING]);
This will capture reclaimers. It will also capture tasks that called
psi_memstall_enter() and are about to sleep, but this should be
negligible noise.
Signed-off-by: Brian Chen <brianchen118@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lore.kernel.org/r/20211110213312.310243-1-brianchen118@gmail.com
Adds accounting for "forced idle" time, which is time where a cookie'd
task forces its SMT sibling to idle, despite the presence of runnable
tasks.
Forced idle time is one means to measure the cost of enabling core
scheduling (ie. the capacity lost due to the need to force idle).
Forced idle time is attributed to the thread responsible for causing
the forced idle.
A few details:
- Forced idle time is displayed via /proc/PID/sched. It also requires
that schedstats is enabled.
- Forced idle is only accounted when a sibling hyperthread is held
idle despite the presence of runnable tasks. No time is charged if
a sibling is idle but has no runnable tasks.
- Tasks with 0 cookie are never charged forced idle.
- For SMT > 2, we scale the amount of forced idle charged based on the
number of forced idle siblings. Additionally, we split the time up and
evenly charge it to all running tasks, as each is equally responsible
for the forced idle.
Signed-off-by: Josh Don <joshdon@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211018203428.2025792-1-joshdon@google.com
Add the missing SPDX license header to
include/linux/psi.h
include/linux/psi_types.h
kernel/sched/psi.c
Signed-off-by: Liu Xinpeng <liuxp11@chinatelecom.cn>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lore.kernel.org/r/1635133586-84611-2-git-send-email-liuxp11@chinatelecom.cn
Comment in function psi_task_switch,there are two same lines.
...
* runtime state, the cgroup that contains both tasks
* runtime state, the cgroup that contains both tasks
...
Signed-off-by: Liu Xinpeng <liuxp11@chinatelecom.cn>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lore.kernel.org/r/1635133586-84611-1-git-send-email-liuxp11@chinatelecom.cn
Commit c597bfddc9 ("sched: Provide Kconfig support for default dynamic
preempt mode") changed the selectable config names for the preemption
model. This means a config file must now select
CONFIG_PREEMPT_BEHAVIOUR=y
rather than
CONFIG_PREEMPT=y
to get a preemptible kernel. This means all arch config files would need to
be updated - right now they'll all end up with the default
CONFIG_PREEMPT_NONE_BEHAVIOUR.
Rather than touch a good hundred of config files, restore usage of
CONFIG_PREEMPT{_NONE, _VOLUNTARY}. Make them configure:
o The build-time preemption model when !PREEMPT_DYNAMIC
o The default boot-time preemption model when PREEMPT_DYNAMIC
Add siblings of those configs with the _BUILD suffix to unconditionally
designate the build-time preemption model (PREEMPT_DYNAMIC is built with
the "highest" preemption model it supports, aka PREEMPT). Downstream
configs should by now all be depending / selected by CONFIG_PREEMPTION
rather than CONFIG_PREEMPT, so only a few sites need patching up.
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Marco Elver <elver@google.com>
Link: https://lore.kernel.org/r/20211110202448.4054153-2-valentin.schneider@arm.com
Kevin is reporting crashes which point to a use-after-free of a cfs_rq
in update_blocked_averages(). Initial debugging revealed that we've
live cfs_rq's (on_list=1) in an about to be kfree()'d task group in
free_fair_sched_group(). However, it was unclear how that can happen.
His kernel config happened to lead to a layout of struct sched_entity
that put the 'my_q' member directly into the middle of the object
which makes it incidentally overlap with SLUB's freelist pointer.
That, in combination with SLAB_FREELIST_HARDENED's freelist pointer
mangling, leads to a reliable access violation in form of a #GP which
made the UAF fail fast.
Michal seems to have run into the same issue[1]. He already correctly
diagnosed that commit a7b359fc6a ("sched/fair: Correctly insert
cfs_rq's to list on unthrottle") is causing the preconditions for the
UAF to happen by re-adding cfs_rq's also to task groups that have no
more running tasks, i.e. also to dead ones. His analysis, however,
misses the real root cause and it cannot be seen from the crash
backtrace only, as the real offender is tg_unthrottle_up() getting
called via sched_cfs_period_timer() via the timer interrupt at an
inconvenient time.
When unregister_fair_sched_group() unlinks all cfs_rq's from the dying
task group, it doesn't protect itself from getting interrupted. If the
timer interrupt triggers while we iterate over all CPUs or after
unregister_fair_sched_group() has finished but prior to unlinking the
task group, sched_cfs_period_timer() will execute and walk the list of
task groups, trying to unthrottle cfs_rq's, i.e. re-add them to the
dying task group. These will later -- in free_fair_sched_group() -- be
kfree()'ed while still being linked, leading to the fireworks Kevin
and Michal are seeing.
To fix this race, ensure the dying task group gets unlinked first.
However, simply switching the order of unregistering and unlinking the
task group isn't sufficient, as concurrent RCU walkers might still see
it, as can be seen below:
CPU1: CPU2:
: timer IRQ:
: do_sched_cfs_period_timer():
: :
: distribute_cfs_runtime():
: rcu_read_lock();
: :
: unthrottle_cfs_rq():
sched_offline_group(): :
: walk_tg_tree_from(…,tg_unthrottle_up,…):
list_del_rcu(&tg->list); :
(1) : list_for_each_entry_rcu(child, &parent->children, siblings)
: :
(2) list_del_rcu(&tg->siblings); :
: tg_unthrottle_up():
unregister_fair_sched_group(): struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
: :
list_del_leaf_cfs_rq(tg->cfs_rq[cpu]); :
: :
: if (!cfs_rq_is_decayed(cfs_rq) || cfs_rq->nr_running)
(3) : list_add_leaf_cfs_rq(cfs_rq);
: :
: :
: :
: :
: :
(4) : rcu_read_unlock();
CPU 2 walks the task group list in parallel to sched_offline_group(),
specifically, it'll read the soon to be unlinked task group entry at
(1). Unlinking it on CPU 1 at (2) therefore won't prevent CPU 2 from
still passing it on to tg_unthrottle_up(). CPU 1 now tries to unlink
all cfs_rq's via list_del_leaf_cfs_rq() in
unregister_fair_sched_group(). Meanwhile CPU 2 will re-add some of
these at (3), which is the cause of the UAF later on.
To prevent this additional race from happening, we need to wait until
walk_tg_tree_from() has finished traversing the task groups, i.e.
after the RCU read critical section ends in (4). Afterwards we're safe
to call unregister_fair_sched_group(), as each new walk won't see the
dying task group any more.
On top of that, we need to wait yet another RCU grace period after
unregister_fair_sched_group() to ensure print_cfs_stats(), which might
run concurrently, always sees valid objects, i.e. not already free'd
ones.
This patch survives Michal's reproducer[2] for 8h+ now, which used to
trigger within minutes before.
[1] https://lore.kernel.org/lkml/20211011172236.11223-1-mkoutny@suse.com/
[2] https://lore.kernel.org/lkml/20211102160228.GA57072@blackbody.suse.cz/
Fixes: a7b359fc6a ("sched/fair: Correctly insert cfs_rq's to list on unthrottle")
[peterz: shuffle code around a bit]
Reported-by: Kevin Tanguy <kevin.tanguy@corp.ovh.com>
Signed-off-by: Mathias Krause <minipli@grsecurity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Nothing protects the access to the per_cpu variable sd_llc_id. When testing
the same CPU (i.e. this_cpu == that_cpu), a race condition exists with
update_top_cache_domain(). One scenario being:
CPU1 CPU2
==================================================================
per_cpu(sd_llc_id, CPUX) => 0
partition_sched_domains_locked()
detach_destroy_domains()
cpus_share_cache(CPUX, CPUX) update_top_cache_domain(CPUX)
per_cpu(sd_llc_id, CPUX) => 0
per_cpu(sd_llc_id, CPUX) = CPUX
per_cpu(sd_llc_id, CPUX) => CPUX
return false
ttwu_queue_cond() wouldn't catch smp_processor_id() == cpu and the result
is a warning triggered from ttwu_queue_wakelist().
Avoid a such race in cpus_share_cache() by always returning true when
this_cpu == that_cpu.
Fixes: 518cd62341 ("sched: Only queue remote wakeups when crossing cache boundaries")
Reported-by: Jing-Ting Wu <jing-ting.wu@mediatek.com>
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20211104175120.857087-1-vincent.donnefort@arm.com
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Merge tag 'kernel.sys.v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux
Pull prctl updates from Christian Brauner:
"This contains the missing prctl uapi pieces for PR_SCHED_CORE.
In order to activate core scheduling the caller is expected to specify
the scope of the new core scheduling domain.
For example, passing 2 in the 4th argument of
prctl(PR_SCHED_CORE, PR_SCHED_CORE_CREATE, <pid>, 2, 0);
would indicate that the new core scheduling domain encompasses all
tasks in the process group of <pid>. Specifying 0 would only create a
core scheduling domain for the thread identified by <pid> and 2 would
encompass the whole thread-group of <pid>.
Note, the values 0, 1, and 2 correspond to PIDTYPE_PID, PIDTYPE_TGID,
and PIDTYPE_PGID. A first version tried to expose those values
directly to which I objected because:
- PIDTYPE_* is an enum that is kernel internal which we should not
expose to userspace directly.
- PIDTYPE_* indicates what a given struct pid is used for it doesn't
express a scope.
But what the 4th argument of PR_SCHED_CORE prctl() expresses is the
scope of the operation, i.e. the scope of the core scheduling domain
at creation time. So Eugene's patch now simply introduces three new
defines PR_SCHED_CORE_SCOPE_THREAD, PR_SCHED_CORE_SCOPE_THREAD_GROUP,
and PR_SCHED_CORE_SCOPE_PROCESS_GROUP. They simply express what
happens.
This has been on the mailing list for quite a while with all relevant
scheduler folks Cced. I announced multiple times that I'd pick this up
if I don't see or her anyone else doing it. None of this touches
proper scheduler code but only concerns uapi so I think this is fine.
With core scheduling being quite common now for vm managers (e.g.
moving individual vcpu threads into their own core scheduling domain)
and container managers (e.g. moving the init process into its own core
scheduling domain and letting all created children inherit it) having
to rely on raw numbers passed as the 4th argument in prctl() is a bit
annoying and everyone is starting to come up with their own defines"
* tag 'kernel.sys.v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
uapi/linux/prctl: provide macro definitions for the PR_SCHED_CORE type argument
Merge misc updates from Andrew Morton:
"257 patches.
Subsystems affected by this patch series: scripts, ocfs2, vfs, and
mm (slab-generic, slab, slub, kconfig, dax, kasan, debug, pagecache,
gup, swap, memcg, pagemap, mprotect, mremap, iomap, tracing, vmalloc,
pagealloc, memory-failure, hugetlb, userfaultfd, vmscan, tools,
memblock, oom-kill, hugetlbfs, migration, thp, readahead, nommu, ksm,
vmstat, madvise, memory-hotplug, rmap, zsmalloc, highmem, zram,
cleanups, kfence, and damon)"
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (257 commits)
mm/damon: remove return value from before_terminate callback
mm/damon: fix a few spelling mistakes in comments and a pr_debug message
mm/damon: simplify stop mechanism
Docs/admin-guide/mm/pagemap: wordsmith page flags descriptions
Docs/admin-guide/mm/damon/start: simplify the content
Docs/admin-guide/mm/damon/start: fix a wrong link
Docs/admin-guide/mm/damon/start: fix wrong example commands
mm/damon/dbgfs: add adaptive_targets list check before enable monitor_on
mm/damon: remove unnecessary variable initialization
Documentation/admin-guide/mm/damon: add a document for DAMON_RECLAIM
mm/damon: introduce DAMON-based Reclamation (DAMON_RECLAIM)
selftests/damon: support watermarks
mm/damon/dbgfs: support watermarks
mm/damon/schemes: activate schemes based on a watermarks mechanism
tools/selftests/damon: update for regions prioritization of schemes
mm/damon/dbgfs: support prioritization weights
mm/damon/vaddr,paddr: support pageout prioritization
mm/damon/schemes: prioritize regions within the quotas
mm/damon/selftests: support schemes quotas
mm/damon/dbgfs: support quotas of schemes
...
Patch series "Fix NUMA without SMP".
SuperH is the only architecture which still supports NUMA without SMP,
for good reasons (various memories scattered around the address space,
each with varying latencies).
This series fixes two build errors due to variables and functions used
by the NUMA code being provided by SMP-only source files or sections.
This patch (of 2):
If CONFIG_NUMA=y, but CONFIG_SMP=n (e.g. sh/migor_defconfig):
sh4-linux-gnu-ld: mm/page_alloc.o: in function `get_page_from_freelist':
page_alloc.c:(.text+0x2c24): undefined reference to `node_reclaim_distance'
Fix this by moving the declaration of node_reclaim_distance from an
SMP-only to a generic file.
Link: https://lkml.kernel.org/r/cover.1631781495.git.geert+renesas@glider.be
Link: https://lkml.kernel.org/r/6432666a648dde85635341e6c918cee97c97d264.1631781495.git.geert+renesas@glider.be
Fixes: a55c7454a8 ("sched/topology: Improve load balancing on AMD EPYC systems")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Suggested-by: Matt Fleming <matt@codeblueprint.co.uk>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yoshinori Sato <ysato@users.osdn.me>
Cc: Rich Felker <dalias@libc.org>
Cc: Gon Solo <gonsolo@gmail.com>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cross-architecture update to move task_struct::cpu back into thread_info
on arm64, x86, s390, powerpc, and riscv. All Acked by arch maintainers.
Quoting Ard Biesheuvel:
"Move task_struct::cpu back into thread_info
Keeping CPU in task_struct is problematic for architectures that define
raw_smp_processor_id() in terms of this field, as it requires
linux/sched.h to be included, which causes a lot of pain in terms of
circular dependencies (aka 'header soup')
This series moves it back into thread_info (where it came from) for all
architectures that enable THREAD_INFO_IN_TASK, addressing the header
soup issue as well as some pointless differences in the implementations
of task_cpu() and set_task_cpu()."
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Merge tag 'cpu-to-thread_info-v5.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux
Pull thread_info update to move 'cpu' back from task_struct from Kees Cook:
"Cross-architecture update to move task_struct::cpu back into
thread_info on arm64, x86, s390, powerpc, and riscv. All Acked by arch
maintainers.
Quoting Ard Biesheuvel:
'Move task_struct::cpu back into thread_info
Keeping CPU in task_struct is problematic for architectures that
define raw_smp_processor_id() in terms of this field, as it
requires linux/sched.h to be included, which causes a lot of pain
in terms of circular dependencies (aka 'header soup')
This series moves it back into thread_info (where it came from)
for all architectures that enable THREAD_INFO_IN_TASK, addressing
the header soup issue as well as some pointless differences in the
implementations of task_cpu() and set_task_cpu()'"
* tag 'cpu-to-thread_info-v5.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
riscv: rely on core code to keep thread_info::cpu updated
powerpc: smp: remove hack to obtain offset of task_struct::cpu
sched: move CPU field back into thread_info if THREAD_INFO_IN_TASK=y
powerpc: add CPU field to struct thread_info
s390: add CPU field to struct thread_info
x86: add CPU field to struct thread_info
arm64: add CPU field to struct thread_info
- Revert the printk format based wchan() symbol resolution as it can leak
the raw value in case that the symbol is not resolvable.
- Make wchan() more robust and work with all kind of unwinders by
enforcing that the task stays blocked while unwinding is in progress.
- Prevent sched_fork() from accessing an invalid sched_task_group
- Improve asymmetric packing logic
- Extend scheduler statistics to RT and DL scheduling classes and add
statistics for bandwith burst to the SCHED_FAIR class.
- Properly account SCHED_IDLE entities
- Prevent a potential deadlock when initial priority is assigned to a
newly created kthread. A recent change to plug a race between cpuset and
__sched_setscheduler() introduced a new lock dependency which is now
triggered. Break the lock dependency chain by moving the priority
assignment to the thread function.
- Fix the idle time reporting in /proc/uptime for NOHZ enabled systems.
- Improve idle balancing in general and especially for NOHZ enabled
systems.
- Provide proper interfaces for live patching so it does not have to
fiddle with scheduler internals.
- Add cluster aware scheduling support.
- A small set of tweaks for RT (irqwork, wait_task_inactive(), various
scheduler options and delaying mmdrop)
- The usual small tweaks and improvements all over the place
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Merge tag 'sched-core-2021-11-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Thomas Gleixner:
- Revert the printk format based wchan() symbol resolution as it can
leak the raw value in case that the symbol is not resolvable.
- Make wchan() more robust and work with all kind of unwinders by
enforcing that the task stays blocked while unwinding is in progress.
- Prevent sched_fork() from accessing an invalid sched_task_group
- Improve asymmetric packing logic
- Extend scheduler statistics to RT and DL scheduling classes and add
statistics for bandwith burst to the SCHED_FAIR class.
- Properly account SCHED_IDLE entities
- Prevent a potential deadlock when initial priority is assigned to a
newly created kthread. A recent change to plug a race between cpuset
and __sched_setscheduler() introduced a new lock dependency which is
now triggered. Break the lock dependency chain by moving the priority
assignment to the thread function.
- Fix the idle time reporting in /proc/uptime for NOHZ enabled systems.
- Improve idle balancing in general and especially for NOHZ enabled
systems.
- Provide proper interfaces for live patching so it does not have to
fiddle with scheduler internals.
- Add cluster aware scheduling support.
- A small set of tweaks for RT (irqwork, wait_task_inactive(), various
scheduler options and delaying mmdrop)
- The usual small tweaks and improvements all over the place
* tag 'sched-core-2021-11-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (69 commits)
sched/fair: Cleanup newidle_balance
sched/fair: Remove sysctl_sched_migration_cost condition
sched/fair: Wait before decaying max_newidle_lb_cost
sched/fair: Skip update_blocked_averages if we are defering load balance
sched/fair: Account update_blocked_averages in newidle_balance cost
x86: Fix __get_wchan() for !STACKTRACE
sched,x86: Fix L2 cache mask
sched/core: Remove rq_relock()
sched: Improve wake_up_all_idle_cpus() take #2
irq_work: Also rcuwait for !IRQ_WORK_HARD_IRQ on PREEMPT_RT
irq_work: Handle some irq_work in a per-CPU thread on PREEMPT_RT
irq_work: Allow irq_work_sync() to sleep if irq_work() no IRQ support.
sched/rt: Annotate the RT balancing logic irqwork as IRQ_WORK_HARD_IRQ
sched: Add cluster scheduler level for x86
sched: Add cluster scheduler level in core and related Kconfig for ARM64
topology: Represent clusters of CPUs within a die
sched: Disable -Wunused-but-set-variable
sched: Add wrapper for get_wchan() to keep task blocked
x86: Fix get_wchan() to support the ORC unwinder
proc: Use task_is_running() for wchan in /proc/$pid/stat
...
- Move futex code into kernel/futex/ and split up the kitchen sink into
seperate files to make integration of sys_futex_waitv() simpler.
- Add a new sys_futex_waitv() syscall which allows to wait on multiple
futexes. The main use case is emulating Windows' WaitForMultipleObjects
which allows Wine to improve the performance of Windows Games. Also
native Linux games can benefit from this interface as this is a common
wait pattern for this kind of applications.
- Add context to ww_mutex_trylock() to provide a path for i915 to rework
their eviction code step by step without making lockdep upset until the
final steps of rework are completed. It's also useful for regulator and
TTM to avoid dropping locks in the non contended path.
- Lockdep and might_sleep() cleanups and improvements
- A few improvements for the RT substitutions.
- The usual small improvements and cleanups.
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Merge tag 'locking-core-2021-10-31' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking updates from Thomas Gleixner:
- Move futex code into kernel/futex/ and split up the kitchen sink into
seperate files to make integration of sys_futex_waitv() simpler.
- Add a new sys_futex_waitv() syscall which allows to wait on multiple
futexes.
The main use case is emulating Windows' WaitForMultipleObjects which
allows Wine to improve the performance of Windows Games. Also native
Linux games can benefit from this interface as this is a common wait
pattern for this kind of applications.
- Add context to ww_mutex_trylock() to provide a path for i915 to
rework their eviction code step by step without making lockdep upset
until the final steps of rework are completed. It's also useful for
regulator and TTM to avoid dropping locks in the non contended path.
- Lockdep and might_sleep() cleanups and improvements
- A few improvements for the RT substitutions.
- The usual small improvements and cleanups.
* tag 'locking-core-2021-10-31' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (44 commits)
locking: Remove spin_lock_flags() etc
locking/rwsem: Fix comments about reader optimistic lock stealing conditions
locking: Remove rcu_read_{,un}lock() for preempt_{dis,en}able()
locking/rwsem: Disable preemption for spinning region
docs: futex: Fix kernel-doc references
futex: Fix PREEMPT_RT build
futex2: Documentation: Document sys_futex_waitv() uAPI
selftests: futex: Test sys_futex_waitv() wouldblock
selftests: futex: Test sys_futex_waitv() timeout
selftests: futex: Add sys_futex_waitv() test
futex,arm: Wire up sys_futex_waitv()
futex,x86: Wire up sys_futex_waitv()
futex: Implement sys_futex_waitv()
futex: Simplify double_lock_hb()
futex: Split out wait/wake
futex: Split out requeue
futex: Rename mark_wake_futex()
futex: Rename: match_futex()
futex: Rename: hb_waiter_{inc,dec,pending}()
futex: Split out PI futex
...
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Merge tag 'for-5.16/block-2021-10-29' of git://git.kernel.dk/linux-block
Pull block updates from Jens Axboe:
- mq-deadline accounting improvements (Bart)
- blk-wbt timer fix (Andrea)
- Untangle the block layer includes (Christoph)
- Rework the poll support to be bio based, which will enable adding
support for polling for bio based drivers (Christoph)
- Block layer core support for multi-actuator drives (Damien)
- blk-crypto improvements (Eric)
- Batched tag allocation support (me)
- Request completion batching support (me)
- Plugging improvements (me)
- Shared tag set improvements (John)
- Concurrent queue quiesce support (Ming)
- Cache bdev in ->private_data for block devices (Pavel)
- bdev dio improvements (Pavel)
- Block device invalidation and block size improvements (Xie)
- Various cleanups, fixes, and improvements (Christoph, Jackie,
Masahira, Tejun, Yu, Pavel, Zheng, me)
* tag 'for-5.16/block-2021-10-29' of git://git.kernel.dk/linux-block: (174 commits)
blk-mq-debugfs: Show active requests per queue for shared tags
block: improve readability of blk_mq_end_request_batch()
virtio-blk: Use blk_validate_block_size() to validate block size
loop: Use blk_validate_block_size() to validate block size
nbd: Use blk_validate_block_size() to validate block size
block: Add a helper to validate the block size
block: re-flow blk_mq_rq_ctx_init()
block: prefetch request to be initialized
block: pass in blk_mq_tags to blk_mq_rq_ctx_init()
block: add rq_flags to struct blk_mq_alloc_data
block: add async version of bio_set_polled
block: kill DIO_MULTI_BIO
block: kill unused polling bits in __blkdev_direct_IO()
block: avoid extra iter advance with async iocb
block: Add independent access ranges support
blk-mq: don't issue request directly in case that current is to be blocked
sbitmap: silence data race warning
blk-cgroup: synchronize blkg creation against policy deactivation
block: refactor bio_iov_bvec_set()
block: add single bio async direct IO helper
...
update_next_balance() uses sd->last_balance which is not modified by
load_balance() so we can merge the 2 calls in one place.
No functional change
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lore.kernel.org/r/20211019123537.17146-6-vincent.guittot@linaro.org
With a default value of 500us, sysctl_sched_migration_cost is
significanlty higher than the cost of load_balance. Remove the
condition and rely on the sd->max_newidle_lb_cost to abort
newidle_balance.
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lore.kernel.org/r/20211019123537.17146-5-vincent.guittot@linaro.org
Decay max_newidle_lb_cost only when it has not been updated for a while
and ensure to not decay a recently changed value.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lore.kernel.org/r/20211019123537.17146-4-vincent.guittot@linaro.org
In newidle_balance(), the scheduler skips load balance to the new idle cpu
when the 1st sd of this_rq is:
this_rq->avg_idle < sd->max_newidle_lb_cost
Doing a costly call to update_blocked_averages() will not be useful and
simply adds overhead when this condition is true.
Check the condition early in newidle_balance() to skip
update_blocked_averages() when possible.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lore.kernel.org/r/20211019123537.17146-3-vincent.guittot@linaro.org
The time spent to update the blocked load can be significant depending of
the complexity fo the cgroup hierarchy. Take this time into account in
the cost of the 1st load balance of a newly idle cpu.
Also reduce the number of call to sched_clock_cpu() and track more actual
work.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lore.kernel.org/r/20211019123537.17146-2-vincent.guittot@linaro.org
Consolidate the various helpers into a single blk_flush_plug helper that
takes a plk_plug and the from_scheduler bool and switch all callsites to
call it directly. Checks that the plug is non-NULL must be performed by
the caller, something that most already do anyway.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211020144119.142582-5-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Commit f1a0a376ca ("sched/core: Initialize the idle task with
preemption disabled") removed the init_idle() call from
idle_thread_get(). This was the sole call-path on hotplug that resets
the Shadow Call Stack (scs) Stack Pointer (sp).
Not resetting the scs-sp leads to scs overflow after enough hotplug
cycles. Therefore add an explicit scs_task_reset() to the hotplug code
to make sure the scs-sp does get reset on hotplug.
Fixes: f1a0a376ca ("sched/core: Initialize the idle task with preemption disabled")
Signed-off-by: Woody Lin <woodylin@google.com>
[peterz: Changelog]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lore.kernel.org/r/20211012083521.973587-1-woodylin@google.com
Only core.c needs blkdev.h, so move the #include statement there.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20210920123328.1399408-8-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The push-IPI logic for RT tasks expects to be invoked from hardirq
context. One reason is that a RT task on the remote CPU would block the
softirq processing on PREEMPT_RT and so avoid pulling / balancing the RT
tasks as intended.
Annotate root_domain::rto_push_work as IRQ_WORK_HARD_IRQ.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211006111852.1514359-2-bigeasy@linutronix.de
The compilers can't deal with obvious DCE vs that warning, resulting
in code like:
if (0) {
sched sched_statistics *stats;
stats = __schedstats_from_se(se);
...
}
triggering the warning. Kill the warning to make the robots stop
reporting this.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lkml.kernel.org/r/YWWPLnaZGybHsTkv@hirez.programming.kicks-ass.net
Having a stable wchan means the process must be blocked and for it to
stay that way while performing stack unwinding.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk> [arm]
Tested-by: Mark Rutland <mark.rutland@arm.com> [arm64]
Link: https://lkml.kernel.org/r/20211008111626.332092234@infradead.org
There is a small race between copy_process() and sched_fork()
where child->sched_task_group point to an already freed pointer.
parent doing fork() | someone moving the parent
| to another cgroup
-------------------------------+-------------------------------
copy_process()
+ dup_task_struct()<1>
parent move to another cgroup,
and free the old cgroup. <2>
+ sched_fork()
+ __set_task_cpu()<3>
+ task_fork_fair()
+ sched_slice()<4>
In the worst case, this bug can lead to "use-after-free" and
cause panic as shown above:
(1) parent copy its sched_task_group to child at <1>;
(2) someone move the parent to another cgroup and free the old
cgroup at <2>;
(3) the sched_task_group and cfs_rq that belong to the old cgroup
will be accessed at <3> and <4>, which cause a panic:
[] BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
[] PGD 8000001fa0a86067 P4D 8000001fa0a86067 PUD 2029955067 PMD 0
[] Oops: 0000 [#1] SMP PTI
[] CPU: 7 PID: 648398 Comm: ebizzy Kdump: loaded Tainted: G OE --------- - - 4.18.0.x86_64+ #1
[] RIP: 0010:sched_slice+0x84/0xc0
[] Call Trace:
[] task_fork_fair+0x81/0x120
[] sched_fork+0x132/0x240
[] copy_process.part.5+0x675/0x20e0
[] ? __handle_mm_fault+0x63f/0x690
[] _do_fork+0xcd/0x3b0
[] do_syscall_64+0x5d/0x1d0
[] entry_SYSCALL_64_after_hwframe+0x65/0xca
[] RIP: 0033:0x7f04418cd7e1
Between cgroup_can_fork() and cgroup_post_fork(), the cgroup
membership and thus sched_task_group can't change. So update child's
sched_task_group at sched_post_fork() and move task_fork() and
__set_task_cpu() (where accees the sched_task_group) from sched_fork()
to sched_post_fork().
Fixes: 8323f26ce3 ("sched: Fix race in task_group")
Signed-off-by: Zhang Qiao <zhangqiao22@huawei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lkml.kernel.org/r/20210915064030.2231-1-zhangqiao22@huawei.com
numa_distance in cpu_attach_domain() is introduced in
commit b5b217346d ("sched/topology: Warn when NUMA diameter > 2")
to warn user when NUMA diameter > 2 as we'll misrepresent
the scheduler topology structures at that time. This is
fixed by Barry in commit 585b6d2723 ("sched/topology: fix the issue
groups don't span domain->span for NUMA diameter > 2") and
numa_distance is unused now. So remove it.
Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Barry Song <baohua@kernel.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lore.kernel.org/r/20210915063158.80639-1-yangyicong@hisilicon.com
Fix a few comments to help understand them better.
Signed-off-by: Bharata B Rao <bharata@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lkml.kernel.org/r/20211004105706.3669-4-bharata@amd.com
numa_group::fault_cpus is actually a pointer to the region
in numa_group::faults[] where NUMA_CPU stats are located.
Remove this redundant member and use numa_group::faults[NUMA_CPU]
directly like it is done for similar per-process numa fault stats.
There is no functionality change due to this commit.
Signed-off-by: Bharata B Rao <bharata@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lkml.kernel.org/r/20211004105706.3669-3-bharata@amd.com
While allocating group fault stats, task_numa_group()
is using a hard coded number 4. Replace this by
NR_NUMA_HINT_FAULT_STATS.
No functionality change in this commit.
Signed-off-by: Bharata B Rao <bharata@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lkml.kernel.org/r/20211004105706.3669-2-bharata@amd.com
Simplify and make wake_up_if_idle() more robust, also don't iterate
the whole machine with preempt_disable() in it's caller:
wake_up_all_idle_cpus().
This prepares for another wake_up_if_idle() user that needs a full
do_idle() cycle.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Vasily Gorbik <gor@linux.ibm.com>
Tested-by: Vasily Gorbik <gor@linux.ibm.com> # on s390
Link: https://lkml.kernel.org/r/20210929152428.769328779@infradead.org
Give try_invoke_on_locked_down_task() a saner name and have it return
an int so that the caller might distinguish between different reasons
of failure.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Vasily Gorbik <gor@linux.ibm.com>
Tested-by: Vasily Gorbik <gor@linux.ibm.com> # on s390
Link: https://lkml.kernel.org/r/20210929152428.649944917@infradead.org
Clarify and tighten try_invoke_on_locked_down_task().
Basically the function calls @func under task_rq_lock(), except it
avoids taking rq->lock when possible.
This makes calling @func unconditional (the function will get renamed
in a later patch to remove the try).
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Vasily Gorbik <gor@linux.ibm.com>
Tested-by: Vasily Gorbik <gor@linux.ibm.com> # on s390
Link: https://lkml.kernel.org/r/20210929152428.589323576@infradead.org
When !SCHEDSTATS schedstat_enabled() is an unconditional 0 and the
whole block doesn't exist, however GCC figures the scoped variable
'stats' is unused and complains about it.
Upgrade the warning from -Wunused-variable to -Wunused-but-set-variable
by writing it in two statements. This fixes the build because the new
warning is in W=1.
Given that whole if(0) {} thing, I don't feel motivated to change
things overly much and quite strongly feel this is the compiler being
daft.
Fixes: cb3e971c435d ("sched: Make struct sched_statistics independent of fair sched class")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Since commit 89aafd67f2 ("sched/fair: Use prev instead of new target as recent_used_cpu"),
p->recent_used_cpu is unconditionnaly set with prev.
Fixes: 89aafd67f2 ("sched/fair: Use prev instead of new target as recent_used_cpu")
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lkml.kernel.org/r/20210928103544.27489-1-vincent.guittot@linaro.org
Neither wq_worker_sleeping() nor io_wq_worker_sleeping() require to be invoked
with preemption disabled:
- The worker flag checks operations only need to be serialized against
the worker thread itself.
- The accounting and worker pool operations are serialized with locks.
which means that disabling preemption has neither a reason nor a
value. Remove it and update the stale comment.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Link: https://lkml.kernel.org/r/8735pnafj7.ffs@tglx
Doing cleanups in the tail of schedule() is a latency punishment for the
incoming task. The point of invoking kprobes_task_flush() for a dead task
is that the instances are returned and cannot leak when __schedule() is
kprobed.
Move it into the delayed cleanup.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210928122411.537994026@linutronix.de
The queued remote wakeup mechanism has turned out to be suboptimal for RT
enabled kernels. The maximum latencies go up by a factor of > 5x in certain
scenarious.
This is caused by either long wake lists or by a large number of TTWU IPIs
which are processed back to back.
Disable it for RT.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210928122411.482262764@linutronix.de
Batched task migrations are a source for large latencies as they keep the
scheduler from running while processing the migrations.
Limit the batch size to 8 instead of 32 when running on a RT enabled
kernel.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210928122411.425097596@linutronix.de
mmdrop() is invoked from finish_task_switch() by the incoming task to drop
the mm which was handed over by the previous task. mmdrop() can be quite
expensive which prevents an incoming real-time task from getting useful
work done.
Provide mmdrop_sched() which maps to mmdrop() on !RT kernels. On RT kernels
it delagates the eventually required invocation of __mmdrop() to RCU.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210928122411.648582026@linutronix.de
Make cookie functions static as these are no longer invoked directly
by other code.
No functional change intended.
Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210922085735.52812-1-zhangshaokun@hisilicon.com
