Extend 8fb12156b8 ("init: Pin init task to the boot CPU, initially")
to cover the new PF_NO_SETAFFINITY requirement.
While there, move wait_for_completion(&kthreadd_done) into kernel_init()
to make it absolutely clear it is the very first thing done by the init
thread.
Fixes: 570a752b7a ("lib/smp_processor_id: Use is_percpu_thread() instead of nr_cpus_allowed")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Tested-by: Valentin Schneider <valentin.schneider@arm.com>
Tested-by: Borislav Petkov <bp@alien8.de>
Link: https://lkml.kernel.org/r/YLS4mbKUrA3Gnb4t@hirez.programming.kicks-ass.net
fair_sched_class->next no longer exists since commit:
a87e749e8f ("sched: Remove struct sched_class::next field").
Now the sched_class order is specified by the linker script.
Rewrite the comment in a more generic way.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210519063709.323162-1-masahiroy@kernel.org
cpu_cgroup_css_online() calls cpu_util_update_eff() without holding the
uclamp_mutex or rcu_read_lock() like other call sites, which is
a mistake.
The uclamp_mutex is required to protect against concurrent reads and
writes that could update the cgroup hierarchy.
The rcu_read_lock() is required to traverse the cgroup data structures
in cpu_util_update_eff().
Surround the caller with the required locks and add some asserts to
better document the dependency in cpu_util_update_eff().
Fixes: 7226017ad3 ("sched/uclamp: Fix a bug in propagating uclamp value in new cgroups")
Reported-by: Quentin Perret <qperret@google.com>
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210510145032.1934078-3-qais.yousef@arm.com
cpu.uclamp.min is a protection as described in cgroup-v2 Resource
Distribution Model
Documentation/admin-guide/cgroup-v2.rst
which means we try our best to preserve the minimum performance point of
tasks in this group. See full description of cpu.uclamp.min in the
cgroup-v2.rst.
But the current implementation makes it a limit, which is not what was
intended.
For example:
tg->cpu.uclamp.min = 20%
p0->uclamp[UCLAMP_MIN] = 0
p1->uclamp[UCLAMP_MIN] = 50%
Previous Behavior (limit):
p0->effective_uclamp = 0
p1->effective_uclamp = 20%
New Behavior (Protection):
p0->effective_uclamp = 20%
p1->effective_uclamp = 50%
Which is inline with how protections should work.
With this change the cgroup and per-task behaviors are the same, as
expected.
Additionally, we remove the confusing relationship between cgroup and
!user_defined flag.
We don't want for example RT tasks that are boosted by default to max to
change their boost value when they attach to a cgroup. If a cgroup wants
to limit the max performance point of tasks attached to it, then
cpu.uclamp.max must be set accordingly.
Or if they want to set different boost value based on cgroup, then
sysctl_sched_util_clamp_min_rt_default must be used to NOT boost to max
and set the right cpu.uclamp.min for each group to let the RT tasks
obtain the desired boost value when attached to that group.
As it stands the dependency on !user_defined flag adds an extra layer of
complexity that is not required now cpu.uclamp.min behaves properly as
a protection.
The propagation model of effective cpu.uclamp.min in child cgroups as
implemented by cpu_util_update_eff() is still correct. The parent
protection sets an upper limit of what the child cgroups will
effectively get.
Fixes: 3eac870a32 (sched/uclamp: Use TG's clamps to restrict TASK's clamps)
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210510145032.1934078-2-qais.yousef@arm.com
For all intents and purposes, the idle task is a per-CPU kthread. It isn't
created via the same route as other pcpu kthreads however, and as a result
it is missing a few bells and whistles: it fails kthread_is_per_cpu() and
it doesn't have PF_NO_SETAFFINITY set.
Fix the former by giving the idle task a kthread struct along with the
KTHREAD_IS_PER_CPU flag. This requires some extra iffery as init_idle()
call be called more than once on the same idle task.
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210510151024.2448573-2-valentin.schneider@arm.com
Creating 2**32 tasks to wait in D-state is impossible and wasteful.
Return "unsigned int" and save on REX prefixes.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210422200228.1423391-2-adobriyan@gmail.com
Creating 2**32 tasks is impossible due to futex pid limits and wasteful
anyway. Nobody has done it.
Bring nr_running() into 32-bit world to save on REX prefixes.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210422200228.1423391-1-adobriyan@gmail.com
As pointed out by commit
de9b8f5dcb ("sched: Fix crash trying to dequeue/enqueue the idle thread")
init_idle() can and will be invoked more than once on the same idle
task. At boot time, it is invoked for the boot CPU thread by
sched_init(). Then smp_init() creates the threads for all the secondary
CPUs and invokes init_idle() on them.
As the hotplug machinery brings the secondaries to life, it will issue
calls to idle_thread_get(), which itself invokes init_idle() yet again.
In this case it's invoked twice more per secondary: at _cpu_up(), and at
bringup_cpu().
Given smp_init() already initializes the idle tasks for all *possible*
CPUs, no further initialization should be required. Now, removing
init_idle() from idle_thread_get() exposes some interesting expectations
with regards to the idle task's preempt_count: the secondary startup always
issues a preempt_disable(), requiring some reset of the preempt count to 0
between hot-unplug and hotplug, which is currently served by
idle_thread_get() -> idle_init().
Given the idle task is supposed to have preemption disabled once and never
see it re-enabled, it seems that what we actually want is to initialize its
preempt_count to PREEMPT_DISABLED and leave it there. Do that, and remove
init_idle() from idle_thread_get().
Secondary startups were patched via coccinelle:
@begone@
@@
-preempt_disable();
...
cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210512094636.2958515-1-valentin.schneider@arm.com
In order to not have to use pid_struct, create a new, smaller,
structure to manage task cookies for core scheduling.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Don Hiatt <dhiatt@digitalocean.com>
Tested-by: Hongyu Ning <hongyu.ning@linux.intel.com>
Tested-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210422123308.919768100@infradead.org
When a sibling is forced-idle to match the core-cookie; search for
matching tasks to fill the core.
rcu_read_unlock() can incur an infrequent deadlock in
sched_core_balance(). Fix this by using the RCU-sched flavor instead.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Don Hiatt <dhiatt@digitalocean.com>
Tested-by: Hongyu Ning <hongyu.ning@linux.intel.com>
Tested-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210422123308.800048269@infradead.org
During force-idle, we end up doing cross-cpu comparison of vruntimes
during pick_next_task. If we simply compare (vruntime-min_vruntime)
across CPUs, and if the CPUs only have 1 task each, we will always
end up comparing 0 with 0 and pick just one of the tasks all the time.
This starves the task that was not picked. To fix this, take a snapshot
of the min_vruntime when entering force idle and use it for comparison.
This min_vruntime snapshot will only be used for cross-CPU vruntime
comparison, and nothing else.
A note about the min_vruntime snapshot and force idling:
During selection:
When we're not fi, we need to update snapshot.
when we're fi and we were not fi, we must update snapshot.
When we're fi and we were already fi, we must not update snapshot.
Which gives:
fib fi update
0 0 1
0 1 1
1 0 1
1 1 0
Where:
fi: force-idled now
fib: force-idled before
So the min_vruntime snapshot needs to be updated when: !(fib && fi).
Also, the cfs_prio_less() function needs to be aware of whether the
core is in force idle or not, since it will be use this information to
know whether to advance a cfs_rq's min_vruntime_fi in the hierarchy.
So pass this information along via pick_task() -> prio_less().
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Don Hiatt <dhiatt@digitalocean.com>
Tested-by: Hongyu Ning <hongyu.ning@linux.intel.com>
Tested-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210422123308.738542617@infradead.org
The rationale is as follows. In the core-wide pick logic, even if
need_sync == false, we need to go look at other CPUs (non-local CPUs)
to see if they could be running RT.
Say the RQs in a particular core look like this:
Let CFS1 and CFS2 be 2 tagged CFS tags.
Let RT1 be an untagged RT task.
rq0 rq1
CFS1 (tagged) RT1 (no tag)
CFS2 (tagged)
Say schedule() runs on rq0. Now, it will enter the above loop and
pick_task(RT) will return NULL for 'p'. It will enter the above if()
block and see that need_sync == false and will skip RT entirely.
The end result of the selection will be (say prio(CFS1) > prio(CFS2)):
rq0 rq1
CFS1 IDLE
When it should have selected:
rq0 rq1
IDLE RT
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Don Hiatt <dhiatt@digitalocean.com>
Tested-by: Hongyu Ning <hongyu.ning@linux.intel.com>
Tested-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210422123308.678425748@infradead.org
If there is only one long running local task and the sibling is
forced idle, it might not get a chance to run until a schedule
event happens on any cpu in the core.
So we check for this condition during a tick to see if a sibling
is starved and then give it a chance to schedule.
Signed-off-by: Vineeth Pillai <viremana@linux.microsoft.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Don Hiatt <dhiatt@digitalocean.com>
Tested-by: Hongyu Ning <hongyu.ning@linux.intel.com>
Tested-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210422123308.617407840@infradead.org
Instead of only selecting a local task, select a task for all SMT
siblings for every reschedule on the core (irrespective which logical
CPU does the reschedule).
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Don Hiatt <dhiatt@digitalocean.com>
Tested-by: Hongyu Ning <hongyu.ning@linux.intel.com>
Tested-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210422123308.557559654@infradead.org
Introduce task_struct::core_cookie as an opaque identifier for core
scheduling. When enabled; core scheduling will only allow matching
task to be on the core; where idle matches everything.
When task_struct::core_cookie is set (and core scheduling is enabled)
these tasks are indexed in a second RB-tree, first on cookie value
then on scheduling function, such that matching task selection always
finds the most elegible match.
NOTE: *shudder* at the overhead...
NOTE: *sigh*, a 3rd copy of the scheduling function; the alternative
is per class tracking of cookies and that just duplicates a lot of
stuff for no raisin (the 2nd copy lives in the rt-mutex PI code).
[Joel: folded fixes]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Don Hiatt <dhiatt@digitalocean.com>
Tested-by: Hongyu Ning <hongyu.ning@linux.intel.com>
Tested-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210422123308.496975854@infradead.org
Stuff the meat of sched_core_put() into a work such that we can use
sched_core_put() from atomic context.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Don Hiatt <dhiatt@digitalocean.com>
Tested-by: Hongyu Ning <hongyu.ning@linux.intel.com>
Tested-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210422123308.377455632@infradead.org
rq_lockp() includes a static_branch(), which is asm-goto, which is
asm volatile which defeats regular CSE. This means that:
if (!static_branch(&foo))
return simple;
if (static_branch(&foo) && cond)
return complex;
Doesn't fold and we get horrible code. Introduce __rq_lockp() without
the static_branch() on.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Don Hiatt <dhiatt@digitalocean.com>
Tested-by: Hongyu Ning <hongyu.ning@linux.intel.com>
Tested-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210422123308.316696988@infradead.org
Introduce the basic infrastructure to have a core wide rq->lock.
This relies on the rq->__lock order being in increasing CPU number
(inside a core). It is also constrained to SMT8 per lockdep (and
SMT256 per preempt_count).
Luckily SMT8 is the max supported SMT count for Linux (Mips, Sparc and
Power are known to have this).
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Don Hiatt <dhiatt@digitalocean.com>
Tested-by: Hongyu Ning <hongyu.ning@linux.intel.com>
Tested-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/YJUNfzSgptjX7tG6@hirez.programming.kicks-ass.net
When switching on core-sched, CPUs need to agree which lock to use for
their RQ.
The new rule will be that rq->core_enabled will be toggled while
holding all rq->__locks that belong to a core. This means we need to
double check the rq->core_enabled value after each lock acquire and
retry if it changed.
This also has implications for those sites that take multiple RQ
locks, they need to be careful that the second lock doesn't end up
being the first lock.
Verify the lock pointer after acquiring the first lock, because if
they're on the same core, holding any of the rq->__lock instances will
pin the core state.
While there, change the rq->__lock order to CPU number, instead of rq
address, this greatly simplifies the next patch.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Don Hiatt <dhiatt@digitalocean.com>
Tested-by: Hongyu Ning <hongyu.ning@linux.intel.com>
Tested-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/YJUNY0dmrJMD/BIm@hirez.programming.kicks-ass.net
In preparation of playing games with rq->lock, abstract the thing
using an accessor.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Don Hiatt <dhiatt@digitalocean.com>
Tested-by: Hongyu Ning <hongyu.ning@linux.intel.com>
Tested-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210422123308.136465446@infradead.org
In prepration for playing games with rq->lock, add some rq_lock
wrappers.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Don Hiatt <dhiatt@digitalocean.com>
Tested-by: Hongyu Ning <hongyu.ning@linux.intel.com>
Tested-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20210422123308.075967879@infradead.org
container_of() can never return NULL - so don't check for it pointlessly.
[ mingo: Twiddled the changelog. ]
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210510161522.GA32644@redhat.com
Util-clamp places tasks in different buckets based on their clamp values
for performance reasons. However, the size of buckets is currently
computed using a rounding division, which can lead to an off-by-one
error in some configurations.
For instance, with 20 buckets, the bucket size will be 1024/20=51. A
task with a clamp of 1024 will be mapped to bucket id 1024/51=20. Sadly,
correct indexes are in range [0,19], hence leading to an out of bound
memory access.
Clamp the bucket id to fix the issue.
Fixes: 69842cba9a ("sched/uclamp: Add CPU's clamp buckets refcounting")
Suggested-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lkml.kernel.org/r/20210430151412.160913-1-qperret@google.com
- Clean up SCHED_DEBUG: move the decades old mess of sysctl, procfs and debugfs interfaces
to a unified debugfs interface.
- Signals: Allow caching one sigqueue object per task, to improve performance & latencies.
- Improve newidle_balance() irq-off latencies on systems with a large number of CPU cgroups.
- Improve energy-aware scheduling
- Improve the PELT metrics for certain workloads
- Reintroduce select_idle_smt() to improve load-balancing locality - but without the previous
regressions
- Add 'scheduler latency debugging': warn after long periods of pending need_resched. This
is an opt-in feature that requires the enabling of the LATENCY_WARN scheduler feature,
or the use of the resched_latency_warn_ms=xx boot parameter.
- CPU hotplug fixes for HP-rollback, and for the 'fail' interface. Fix remaining
balance_push() vs. hotplug holes/races
- PSI fixes, plus allow /proc/pressure/ files to be written by CAP_SYS_RESOURCE tasks as well
- Fix/improve various load-balancing corner cases vs. capacity margins
- Fix sched topology on systems with NUMA diameter of 3 or above
- Fix PF_KTHREAD vs to_kthread() race
- Minor rseq optimizations
- Misc cleanups, optimizations, fixes and smaller updates
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-core-2021-04-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
- Clean up SCHED_DEBUG: move the decades old mess of sysctl, procfs and
debugfs interfaces to a unified debugfs interface.
- Signals: Allow caching one sigqueue object per task, to improve
performance & latencies.
- Improve newidle_balance() irq-off latencies on systems with a large
number of CPU cgroups.
- Improve energy-aware scheduling
- Improve the PELT metrics for certain workloads
- Reintroduce select_idle_smt() to improve load-balancing locality -
but without the previous regressions
- Add 'scheduler latency debugging': warn after long periods of pending
need_resched. This is an opt-in feature that requires the enabling of
the LATENCY_WARN scheduler feature, or the use of the
resched_latency_warn_ms=xx boot parameter.
- CPU hotplug fixes for HP-rollback, and for the 'fail' interface. Fix
remaining balance_push() vs. hotplug holes/races
- PSI fixes, plus allow /proc/pressure/ files to be written by
CAP_SYS_RESOURCE tasks as well
- Fix/improve various load-balancing corner cases vs. capacity margins
- Fix sched topology on systems with NUMA diameter of 3 or above
- Fix PF_KTHREAD vs to_kthread() race
- Minor rseq optimizations
- Misc cleanups, optimizations, fixes and smaller updates
* tag 'sched-core-2021-04-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (61 commits)
cpumask/hotplug: Fix cpu_dying() state tracking
kthread: Fix PF_KTHREAD vs to_kthread() race
sched/debug: Fix cgroup_path[] serialization
sched,psi: Handle potential task count underflow bugs more gracefully
sched: Warn on long periods of pending need_resched
sched/fair: Move update_nohz_stats() to the CONFIG_NO_HZ_COMMON block to simplify the code & fix an unused function warning
sched/debug: Rename the sched_debug parameter to sched_verbose
sched,fair: Alternative sched_slice()
sched: Move /proc/sched_debug to debugfs
sched,debug: Convert sysctl sched_domains to debugfs
debugfs: Implement debugfs_create_str()
sched,preempt: Move preempt_dynamic to debug.c
sched: Move SCHED_DEBUG sysctl to debugfs
sched: Don't make LATENCYTOP select SCHED_DEBUG
sched: Remove sched_schedstats sysctl out from under SCHED_DEBUG
sched/numa: Allow runtime enabling/disabling of NUMA balance without SCHED_DEBUG
sched: Use cpu_dying() to fix balance_push vs hotplug-rollback
cpumask: Introduce DYING mask
cpumask: Make cpu_{online,possible,present,active}() inline
rseq: Optimise rseq_get_rseq_cs() and clear_rseq_cs()
...
- rtmutex cleanup & spring cleaning pass that removes ~400 lines of code
- Futex simplifications & cleanups
- Add debugging to the CSD code, to help track down a tenacious race (or hw problem)
- Add lockdep_assert_not_held(), to allow code to require a lock to not be held,
and propagate this into the ath10k driver
- Misc LKMM documentation updates
- Misc KCSAN updates: cleanups & documentation updates
- Misc fixes and cleanups
- Fix locktorture bugs with ww_mutexes
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'locking-core-2021-04-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking updates from Ingo Molnar:
- rtmutex cleanup & spring cleaning pass that removes ~400 lines of
code
- Futex simplifications & cleanups
- Add debugging to the CSD code, to help track down a tenacious race
(or hw problem)
- Add lockdep_assert_not_held(), to allow code to require a lock to not
be held, and propagate this into the ath10k driver
- Misc LKMM documentation updates
- Misc KCSAN updates: cleanups & documentation updates
- Misc fixes and cleanups
- Fix locktorture bugs with ww_mutexes
* tag 'locking-core-2021-04-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (44 commits)
kcsan: Fix printk format string
static_call: Relax static_call_update() function argument type
static_call: Fix unused variable warn w/o MODULE
locking/rtmutex: Clean up signal handling in __rt_mutex_slowlock()
locking/rtmutex: Restrict the trylock WARN_ON() to debug
locking/rtmutex: Fix misleading comment in rt_mutex_postunlock()
locking/rtmutex: Consolidate the fast/slowpath invocation
locking/rtmutex: Make text section and inlining consistent
locking/rtmutex: Move debug functions as inlines into common header
locking/rtmutex: Decrapify __rt_mutex_init()
locking/rtmutex: Remove pointless CONFIG_RT_MUTEXES=n stubs
locking/rtmutex: Inline chainwalk depth check
locking/rtmutex: Move rt_mutex_debug_task_free() to rtmutex.c
locking/rtmutex: Remove empty and unused debug stubs
locking/rtmutex: Consolidate rt_mutex_init()
locking/rtmutex: Remove output from deadlock detector
locking/rtmutex: Remove rtmutex deadlock tester leftovers
locking/rtmutex: Remove rt_mutex_timed_lock()
MAINTAINERS: Add myself as futex reviewer
locking/mutex: Remove repeated declaration
...
The kthread_is_per_cpu() construct relies on only being called on
PF_KTHREAD tasks (per the WARN in to_kthread). This gives rise to the
following usage pattern:
if ((p->flags & PF_KTHREAD) && kthread_is_per_cpu(p))
However, as reported by syzcaller, this is broken. The scenario is:
CPU0 CPU1 (running p)
(p->flags & PF_KTHREAD) // true
begin_new_exec()
me->flags &= ~(PF_KTHREAD|...);
kthread_is_per_cpu(p)
to_kthread(p)
WARN(!(p->flags & PF_KTHREAD) <-- *SPLAT*
Introduce __to_kthread() that omits the WARN and is sure to check both
values.
Use this to remove the problematic pattern for kthread_is_per_cpu()
and fix a number of other kthread_*() functions that have similar
issues but are currently not used in ways that would expose the
problem.
Notably kthread_func() is only ever called on 'current', while
kthread_probe_data() is only used for PF_WQ_WORKER, which implies the
task is from kthread_create*().
Fixes: ac687e6e8c ("kthread: Extract KTHREAD_IS_PER_CPU")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <Valentin.Schneider@arm.com>
Link: https://lkml.kernel.org/r/YH6WJc825C4P0FCK@hirez.programming.kicks-ass.net
CPU scheduler marks need_resched flag to signal a schedule() on a
particular CPU. But, schedule() may not happen immediately in cases
where the current task is executing in the kernel mode (no
preemption state) for extended periods of time.
This patch adds a warn_on if need_resched is pending for more than the
time specified in sysctl resched_latency_warn_ms. If it goes off, it is
likely that there is a missing cond_resched() somewhere. Monitoring is
done via the tick and the accuracy is hence limited to jiffy scale. This
also means that we won't trigger the warning if the tick is disabled.
This feature (LATENCY_WARN) is default disabled.
Signed-off-by: Paul Turner <pjt@google.com>
Signed-off-by: Josh Don <joshdon@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210416212936.390566-1-joshdon@google.com
Move the #ifdef SCHED_DEBUG bits to kernel/sched/debug.c in order to
collect all the debugfs bits.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210412102001.353833279@infradead.org
Stop polluting sysctl with undocumented knobs that really are debug
only, move them all to /debug/sched/ along with the existing
/debug/sched_* files that already exist.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Tested-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210412102001.287610138@infradead.org
Use the new cpu_dying() state to simplify and fix the balance_push()
vs CPU hotplug rollback state.
Specifically, we currently rely on notifiers sched_cpu_dying() /
sched_cpu_activate() to terminate balance_push, however if the
cpu_down() fails when we're past sched_cpu_deactivate(), it should
terminate balance_push at that point and not wait until we hit
sched_cpu_activate().
Similarly, when cpu_up() fails and we're going back down, balance_push
should be active, where it currently is not.
So instead, make sure balance_push is enabled below SCHED_AP_ACTIVE
(when !cpu_active()), and gate it's utility with cpu_dying().
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/YHgAYef83VQhKdC2@hirez.programming.kicks-ass.net
Pull ARM cpufreq updates for v5.13 from Viresh Kumar:
"- Fix typos in s5pv210 cpufreq driver (Bhaskar Chowdhury).
- Armada 37xx: Fix cpufreq changing base CPU speed to 800 MHz from
1000 MHz (Pali Rohár and Marek Behún).
- cpufreq-dt: Return -EPROBE_DEFER on failure to add table (Quanyang
Wang).
- Minor cleanup in cppc driver (Tom Saeger).
- Add frequency invariance support for CPPC driver and generalize
freq invariance support arch-topology driver (Viresh Kumar)."
* 'cpufreq/arm/linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/vireshk/pm:
cpufreq: armada-37xx: Fix module unloading
cpufreq: armada-37xx: Remove cur_frequency variable
cpufreq: armada-37xx: Fix determining base CPU frequency
cpufreq: armada-37xx: Fix driver cleanup when registration failed
clk: mvebu: armada-37xx-periph: Fix workaround for switching from L1 to L0
clk: mvebu: armada-37xx-periph: Fix switching CPU freq from 250 Mhz to 1 GHz
cpufreq: armada-37xx: Fix the AVS value for load L1
clk: mvebu: armada-37xx-periph: remove .set_parent method for CPU PM clock
cpufreq: armada-37xx: Fix setting TBG parent for load levels
cpufreq: dt: dev_pm_opp_of_cpumask_add_table() may return -EPROBE_DEFER
cpufreq: cppc: simplify default delay_us setting
cpufreq: Rudimentary typos fix in the file s5pv210-cpufreq.c
cpufreq: CPPC: Add support for frequency invariance
arch_topology: Export arch_freq_scale and helpers
arch_topology: Allow multiple entities to provide sched_freq_tick() callback
arch_topology: Rename freq_scale as arch_freq_scale
static_call_update() had stronger type requirements than regular C,
relax them to match. Instead of requiring the @func argument has the
exact matching type, allow any type which C is willing to promote to the
right (function) pointer type. Specifically this allows (void *)
arguments.
This cleans up a bunch of static_call_update() callers for
PREEMPT_DYNAMIC and should get around silly GCC11 warnings for free.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/YFoN7nCl8OfGtpeh@hirez.programming.kicks-ass.net
-1 is -EPERM which is a somewhat odd error to return from
sched_dynamic_write(). No other callers care about which negative
value is used.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: https://lore.kernel.org/r/20210325004515.531631-2-linux@rasmusvillemoes.dk
Use the enum names which are also what is used in the switch() in
sched_dynamic_update().
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: https://lore.kernel.org/r/20210325004515.531631-1-linux@rasmusvillemoes.dk
The Frequency Invariance Engine (FIE) is providing a frequency scaling
correction factor that helps achieve more accurate load-tracking.
Normally, this scaling factor can be obtained directly with the help of
the cpufreq drivers as they know the exact frequency the hardware is
running at. But that isn't the case for CPPC cpufreq driver.
Another way of obtaining that is using the arch specific counter
support, which is already present in kernel, but that hardware is
optional for platforms.
This patch updates the CPPC driver to register itself with the topology
core to provide its own implementation (cppc_scale_freq_tick()) of
topology_scale_freq_tick() which gets called by the scheduler on every
tick. Note that the arch specific counters have higher priority than
CPPC counters, if available, though the CPPC driver doesn't need to have
any special handling for that.
On an invocation of cppc_scale_freq_tick(), we schedule an irq work
(since we reach here from hard-irq context), which then schedules a
normal work item and cppc_scale_freq_workfn() updates the per_cpu
arch_freq_scale variable based on the counter updates since the last
tick.
To allow platforms to disable this CPPC counter-based frequency
invariance support, this is all done under CONFIG_ACPI_CPPC_CPUFREQ_FIE,
which is enabled by default.
This also exports sched_setattr_nocheck() as the CPPC driver can be
built as a module.
Cc: linux-acpi@vger.kernel.org
Reviewed-by: Ionela Voinescu <ionela.voinescu@arm.com>
Tested-by: Ionela Voinescu <ionela.voinescu@arm.com>
Tested-by: Vincent Guittot <vincent.guittot@linaro.org>
Acked-by: Rafael J. Wysocki <rafael@kernel.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Fix ~42 single-word typos in scheduler code comments.
We have accumulated a few fun ones over the years. :-)
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: linux-kernel@vger.kernel.org
Since 565790d28b (sched: Fix balance_callback(), 2020-05-11), there
is no longer a need to reuse the result value of the call to finish_task_switch()
inside schedule_tail(), therefore the variable used to hold that value
(rq) is no longer needed.
Signed-off-by: Edmundo Carmona Antoranz <eantoranz@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210306210739.1370486-1-eantoranz@gmail.com
Move the reclaim detection from the timer tick to the task state
tracking machinery using the recently added ONCPU state. And we
also add task psi_flags changes checking in the psi_task_switch()
optimization to update the parents properly.
In terms of performance and cost, this ONCPU task state tracking
is not cheaper than previous timer tick in aggregate. But the code is
simpler and shorter this way, so it's a maintainability win. And
Johannes did some testing with perf bench, the performace and cost
changes would be acceptable for real workloads.
Thanks to Johannes Weiner for pointing out the psi_task_switch()
optimization things and the clearer changelog.
Co-developed-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lkml.kernel.org/r/20210303034659.91735-3-zhouchengming@bytedance.com
Instead of waking up a random and already idle CPU, we can take advantage
of this_cpu being about to enter idle to run the ILB and update the
blocked load.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210224133007.28644-7-vincent.guittot@linaro.org
Now that we have set_affinity_pending::stop_pending to indicate if a
stopper is in progress, and we have the guarantee that if that stopper
exists, it will (eventually) complete our @pending we can simplify the
refcount scheme by no longer counting the stopper thread.
Fixes: 6d337eab04 ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Cc: stable@kernel.org
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210224131355.724130207@infradead.org
Consider:
sched_setaffinity(p, X); sched_setaffinity(p, Y);
Then the first will install p->migration_pending = &my_pending; and
issue stop_one_cpu_nowait(pending); and the second one will read
p->migration_pending and _also_ issue: stop_one_cpu_nowait(pending),
the _SAME_ @pending.
This causes stopper list corruption.
Add set_affinity_pending::stop_pending, to indicate if a stopper is in
progress.
Fixes: 6d337eab04 ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Cc: stable@kernel.org
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210224131355.649146419@infradead.org
When the purpose of migration_cpu_stop() is to migrate the task to
'any' valid CPU, don't migrate the task when it's already running on a
valid CPU.
Fixes: 6d337eab04 ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Cc: stable@kernel.org
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210224131355.569238629@infradead.org
The SCA_MIGRATE_ENABLE and task_running() cases are almost identical,
collapse them to avoid further duplication.
Fixes: 6d337eab04 ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Cc: stable@kernel.org
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210224131355.500108964@infradead.org
Since, when ->stop_pending, only the stopper can uninstall
p->migration_pending. This could simplify a few ifs, because:
(pending != NULL) => (pending == p->migration_pending)
Also, the fatty comment above affine_move_task() probably needs a bit
of gardening.
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
When affine_move_task() issues a migration_cpu_stop(), the purpose of
that function is to complete that @pending, not any random other
p->migration_pending that might have gotten installed since.
This realization much simplifies migration_cpu_stop() and allows
further necessary steps to fix all this as it provides the guarantee
that @pending's stopper will complete @pending (and not some random
other @pending).
Fixes: 6d337eab04 ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Cc: stable@kernel.org
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210224131355.430014682@infradead.org
When affine_move_task(p) is called on a running task @p, which is not
otherwise already changing affinity, we'll first set
p->migration_pending and then do:
stop_one_cpu(cpu_of_rq(rq), migration_cpu_stop, &arg);
This then gets us to migration_cpu_stop() running on the CPU that was
previously running our victim task @p.
If we find that our task is no longer on that runqueue (this can
happen because of a concurrent migration due to load-balance etc.),
then we'll end up at the:
} else if (dest_cpu < 1 || pending) {
branch. Which we'll take because we set pending earlier. Here we first
check if the task @p has already satisfied the affinity constraints,
if so we bail early [A]. Otherwise we'll reissue migration_cpu_stop()
onto the CPU that is now hosting our task @p:
stop_one_cpu_nowait(cpu_of(rq), migration_cpu_stop,
&pending->arg, &pending->stop_work);
Except, we've never initialized pending->arg, which will be all 0s.
This then results in running migration_cpu_stop() on the next CPU with
arg->p == NULL, which gives the by now obvious result of fireworks.
The cure is to change affine_move_task() to always use pending->arg,
furthermore we can use the exact same pattern as the
SCA_MIGRATE_ENABLE case, since we'll block on the pending->done
completion anyway, no point in adding yet another completion in
stop_one_cpu().
This then gives a clear distinction between the two
migration_cpu_stop() use cases:
- sched_exec() / migrate_task_to() : arg->pending == NULL
- affine_move_task() : arg->pending != NULL;
And we can have it ignore p->migration_pending when !arg->pending. Any
stop work from sched_exec() / migrate_task_to() is in addition to stop
works from affine_move_task(), which will be sufficient to issue the
completion.
Fixes: 6d337eab04 ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Cc: stable@kernel.org
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210224131355.357743989@infradead.org
- Support for userspace to emulate Xen hypercalls
- Raise the maximum number of user memslots
- Scalability improvements for the new MMU. Instead of the complex
"fast page fault" logic that is used in mmu.c, tdp_mmu.c uses an
rwlock so that page faults are concurrent, but the code that can run
against page faults is limited. Right now only page faults take the
lock for reading; in the future this will be extended to some
cases of page table destruction. I hope to switch the default MMU
around 5.12-rc3 (some testing was delayed due to Chinese New Year).
- Cleanups for MAXPHYADDR checks
- Use static calls for vendor-specific callbacks
- On AMD, use VMLOAD/VMSAVE to save and restore host state
- Stop using deprecated jump label APIs
- Workaround for AMD erratum that made nested virtualization unreliable
- Support for LBR emulation in the guest
- Support for communicating bus lock vmexits to userspace
- Add support for SEV attestation command
- Miscellaneous cleanups
PPC:
- Support for second data watchpoint on POWER10
- Remove some complex workarounds for buggy early versions of POWER9
- Guest entry/exit fixes
ARM64
- Make the nVHE EL2 object relocatable
- Cleanups for concurrent translation faults hitting the same page
- Support for the standard TRNG hypervisor call
- A bunch of small PMU/Debug fixes
- Simplification of the early init hypercall handling
Non-KVM changes (with acks):
- Detection of contended rwlocks (implemented only for qrwlocks,
because KVM only needs it for x86)
- Allow __DISABLE_EXPORTS from assembly code
- Provide a saner follow_pfn replacements for modules
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
Pull KVM updates from Paolo Bonzini:
"x86:
- Support for userspace to emulate Xen hypercalls
- Raise the maximum number of user memslots
- Scalability improvements for the new MMU.
Instead of the complex "fast page fault" logic that is used in
mmu.c, tdp_mmu.c uses an rwlock so that page faults are concurrent,
but the code that can run against page faults is limited. Right now
only page faults take the lock for reading; in the future this will
be extended to some cases of page table destruction. I hope to
switch the default MMU around 5.12-rc3 (some testing was delayed
due to Chinese New Year).
- Cleanups for MAXPHYADDR checks
- Use static calls for vendor-specific callbacks
- On AMD, use VMLOAD/VMSAVE to save and restore host state
- Stop using deprecated jump label APIs
- Workaround for AMD erratum that made nested virtualization
unreliable
- Support for LBR emulation in the guest
- Support for communicating bus lock vmexits to userspace
- Add support for SEV attestation command
- Miscellaneous cleanups
PPC:
- Support for second data watchpoint on POWER10
- Remove some complex workarounds for buggy early versions of POWER9
- Guest entry/exit fixes
ARM64:
- Make the nVHE EL2 object relocatable
- Cleanups for concurrent translation faults hitting the same page
- Support for the standard TRNG hypervisor call
- A bunch of small PMU/Debug fixes
- Simplification of the early init hypercall handling
Non-KVM changes (with acks):
- Detection of contended rwlocks (implemented only for qrwlocks,
because KVM only needs it for x86)
- Allow __DISABLE_EXPORTS from assembly code
- Provide a saner follow_pfn replacements for modules"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (192 commits)
KVM: x86/xen: Explicitly pad struct compat_vcpu_info to 64 bytes
KVM: selftests: Don't bother mapping GVA for Xen shinfo test
KVM: selftests: Fix hex vs. decimal snafu in Xen test
KVM: selftests: Fix size of memslots created by Xen tests
KVM: selftests: Ignore recently added Xen tests' build output
KVM: selftests: Add missing header file needed by xAPIC IPI tests
KVM: selftests: Add operand to vmsave/vmload/vmrun in svm.c
KVM: SVM: Make symbol 'svm_gp_erratum_intercept' static
locking/arch: Move qrwlock.h include after qspinlock.h
KVM: PPC: Book3S HV: Fix host radix SLB optimisation with hash guests
KVM: PPC: Book3S HV: Ensure radix guest has no SLB entries
KVM: PPC: Don't always report hash MMU capability for P9 < DD2.2
KVM: PPC: Book3S HV: Save and restore FSCR in the P9 path
KVM: PPC: remove unneeded semicolon
KVM: PPC: Book3S HV: Use POWER9 SLBIA IH=6 variant to clear SLB
KVM: PPC: Book3S HV: No need to clear radix host SLB before loading HPT guest
KVM: PPC: Book3S HV: Fix radix guest SLB side channel
KVM: PPC: Book3S HV: Remove support for running HPT guest on RPT host without mixed mode support
KVM: PPC: Book3S HV: Introduce new capability for 2nd DAWR
KVM: PPC: Book3S HV: Add infrastructure to support 2nd DAWR
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