Commit Graph

1446 Commits

Author SHA1 Message Date
Linus Torvalds
cac03ac368 Various fixes: a deadline scheduler fix, a migration fix, a Sparse fix and a comment fix.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-urgent-2022-08-06' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler fixes from Ingo Molnar:
 "Various fixes: a deadline scheduler fix, a migration fix, a Sparse fix
  and a comment fix"

* tag 'sched-urgent-2022-08-06' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/core: Do not requeue task on CPU excluded from cpus_mask
  sched/rt: Fix Sparse warnings due to undefined rt.c declarations
  exit: Fix typo in comment: s/sub-theads/sub-threads
  sched, cpuset: Fix dl_cpu_busy() panic due to empty cs->cpus_allowed
2022-08-06 17:34:06 -07:00
Mel Gorman
751d4cbc43 sched/core: Do not requeue task on CPU excluded from cpus_mask
The following warning was triggered on a large machine early in boot on
a distribution kernel but the same problem should also affect mainline.

   WARNING: CPU: 439 PID: 10 at ../kernel/workqueue.c:2231 process_one_work+0x4d/0x440
   Call Trace:
    <TASK>
    rescuer_thread+0x1f6/0x360
    kthread+0x156/0x180
    ret_from_fork+0x22/0x30
    </TASK>

Commit c6e7bd7afa ("sched/core: Optimize ttwu() spinning on p->on_cpu")
optimises ttwu by queueing a task that is descheduling on the wakelist,
but does not check if the task descheduling is still allowed to run on that CPU.

In this warning, the problematic task is a workqueue rescue thread which
checks if the rescue is for a per-cpu workqueue and running on the wrong CPU.
While this is early in boot and it should be possible to create workers,
the rescue thread may still used if the MAYDAY_INITIAL_TIMEOUT is reached
or MAYDAY_INTERVAL and on a sufficiently large machine, the rescue
thread is being used frequently.

Tracing confirmed that the task should have migrated properly using the
stopper thread to handle the migration. However, a parallel wakeup from udev
running on another CPU that does not share CPU cache observes p->on_cpu and
uses task_cpu(p), queues the task on the old CPU and triggers the warning.

Check that the wakee task that is descheduling is still allowed to run
on its current CPU and if not, wait for the descheduling to complete
and select an allowed CPU.

Fixes: c6e7bd7afa ("sched/core: Optimize ttwu() spinning on p->on_cpu")
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20220804092119.20137-1-mgorman@techsingularity.net
2022-08-04 11:26:13 +02:00
Waiman Long
b6e8d40d43 sched, cpuset: Fix dl_cpu_busy() panic due to empty cs->cpus_allowed
With cgroup v2, the cpuset's cpus_allowed mask can be empty indicating
that the cpuset will just use the effective CPUs of its parent. So
cpuset_can_attach() can call task_can_attach() with an empty mask.
This can lead to cpumask_any_and() returns nr_cpu_ids causing the call
to dl_bw_of() to crash due to percpu value access of an out of bound
CPU value. For example:

	[80468.182258] BUG: unable to handle page fault for address: ffffffff8b6648b0
	  :
	[80468.191019] RIP: 0010:dl_cpu_busy+0x30/0x2b0
	  :
	[80468.207946] Call Trace:
	[80468.208947]  cpuset_can_attach+0xa0/0x140
	[80468.209953]  cgroup_migrate_execute+0x8c/0x490
	[80468.210931]  cgroup_update_dfl_csses+0x254/0x270
	[80468.211898]  cgroup_subtree_control_write+0x322/0x400
	[80468.212854]  kernfs_fop_write_iter+0x11c/0x1b0
	[80468.213777]  new_sync_write+0x11f/0x1b0
	[80468.214689]  vfs_write+0x1eb/0x280
	[80468.215592]  ksys_write+0x5f/0xe0
	[80468.216463]  do_syscall_64+0x5c/0x80
	[80468.224287]  entry_SYSCALL_64_after_hwframe+0x44/0xae

Fix that by using effective_cpus instead. For cgroup v1, effective_cpus
is the same as cpus_allowed. For v2, effective_cpus is the real cpumask
to be used by tasks within the cpuset anyway.

Also update task_can_attach()'s 2nd argument name to cs_effective_cpus to
reflect the change. In addition, a check is added to task_can_attach()
to guard against the possibility that cpumask_any_and() may return a
value >= nr_cpu_ids.

Fixes: 7f51412a41 ("sched/deadline: Fix bandwidth check/update when migrating tasks between exclusive cpusets")
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lore.kernel.org/r/20220803015451.2219567-1-longman@redhat.com
2022-08-03 10:34:26 +02:00
Linus Torvalds
7d9d077c78 RCU pull request for v5.20 (or whatever)
This pull request contains the following branches:
 
 doc.2022.06.21a: Documentation updates.
 
 fixes.2022.07.19a: Miscellaneous fixes.
 
 nocb.2022.07.19a: Callback-offload updates, perhaps most notably a new
 	RCU_NOCB_CPU_DEFAULT_ALL Kconfig option that causes all CPUs to
 	be offloaded at boot time, regardless of kernel boot parameters.
 	This is useful to battery-powered systems such as ChromeOS
 	and Android.  In addition, a new RCU_NOCB_CPU_CB_BOOST kernel
 	boot parameter prevents offloaded callbacks from interfering
 	with real-time workloads and with energy-efficiency mechanisms.
 
 poll.2022.07.21a: Polled grace-period updates, perhaps most notably
 	making these APIs account for both normal and expedited grace
 	periods.
 
 rcu-tasks.2022.06.21a: Tasks RCU updates, perhaps most notably reducing
 	the CPU overhead of RCU tasks trace grace periods by more than
 	a factor of two on a system with 15,000 tasks.	The reduction
 	is expected to increase with the number of tasks, so it seems
 	reasonable to hypothesize that a system with 150,000 tasks might
 	see a 20-fold reduction in CPU overhead.
 
 torture.2022.06.21a: Torture-test updates.
 
 ctxt.2022.07.05a: Updates that merge RCU's dyntick-idle tracking into
 	context tracking, thus reducing the overhead of transitioning to
 	kernel mode from either idle or nohz_full userspace execution
 	for kernels that track context independently of RCU.  This is
 	expected to be helpful primarily for kernels built with
 	CONFIG_NO_HZ_FULL=y.
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Merge tag 'rcu.2022.07.26a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu

Pull RCU updates from Paul McKenney:

 - Documentation updates

 - Miscellaneous fixes

 - Callback-offload updates, perhaps most notably a new
   RCU_NOCB_CPU_DEFAULT_ALL Kconfig option that causes all CPUs to be
   offloaded at boot time, regardless of kernel boot parameters.

   This is useful to battery-powered systems such as ChromeOS and
   Android. In addition, a new RCU_NOCB_CPU_CB_BOOST kernel boot
   parameter prevents offloaded callbacks from interfering with
   real-time workloads and with energy-efficiency mechanisms

 - Polled grace-period updates, perhaps most notably making these APIs
   account for both normal and expedited grace periods

 - Tasks RCU updates, perhaps most notably reducing the CPU overhead of
   RCU tasks trace grace periods by more than a factor of two on a
   system with 15,000 tasks.

   The reduction is expected to increase with the number of tasks, so it
   seems reasonable to hypothesize that a system with 150,000 tasks
   might see a 20-fold reduction in CPU overhead

 - Torture-test updates

 - Updates that merge RCU's dyntick-idle tracking into context tracking,
   thus reducing the overhead of transitioning to kernel mode from
   either idle or nohz_full userspace execution for kernels that track
   context independently of RCU.

   This is expected to be helpful primarily for kernels built with
   CONFIG_NO_HZ_FULL=y

* tag 'rcu.2022.07.26a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu: (98 commits)
  rcu: Add irqs-disabled indicator to expedited RCU CPU stall warnings
  rcu: Diagnose extended sync_rcu_do_polled_gp() loops
  rcu: Put panic_on_rcu_stall() after expedited RCU CPU stall warnings
  rcutorture: Test polled expedited grace-period primitives
  rcu: Add polled expedited grace-period primitives
  rcutorture: Verify that polled GP API sees synchronous grace periods
  rcu: Make Tiny RCU grace periods visible to polled APIs
  rcu: Make polled grace-period API account for expedited grace periods
  rcu: Switch polled grace-period APIs to ->gp_seq_polled
  rcu/nocb: Avoid polling when my_rdp->nocb_head_rdp list is empty
  rcu/nocb: Add option to opt rcuo kthreads out of RT priority
  rcu: Add nocb_cb_kthread check to rcu_is_callbacks_kthread()
  rcu/nocb: Add an option to offload all CPUs on boot
  rcu/nocb: Fix NOCB kthreads spawn failure with rcu_nocb_rdp_deoffload() direct call
  rcu/nocb: Invert rcu_state.barrier_mutex VS hotplug lock locking order
  rcu/nocb: Add/del rdp to iterate from rcuog itself
  rcu/tree: Add comment to describe GP-done condition in fqs loop
  rcu: Initialize first_gp_fqs at declaration in rcu_gp_fqs()
  rcu/kvfree: Remove useless monitor_todo flag
  rcu: Cleanup RCU urgency state for offline CPU
  ...
2022-08-02 19:12:45 -07:00
Linus Torvalds
b349b1181d for-5.20/io_uring-2022-07-29
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Merge tag 'for-5.20/io_uring-2022-07-29' of git://git.kernel.dk/linux-block

Pull io_uring updates from Jens Axboe:

 - As per (valid) complaint in the last merge window, fs/io_uring.c has
   grown quite large these days. io_uring isn't really tied to fs
   either, as it supports a wide variety of functionality outside of
   that.

   Move the code to io_uring/ and split it into files that either
   implement a specific request type, and split some code into helpers
   as well. The code is organized a lot better like this, and io_uring.c
   is now < 4K LOC (me).

 - Deprecate the epoll_ctl opcode. It'll still work, just trigger a
   warning once if used. If we don't get any complaints on this, and I
   don't expect any, then we can fully remove it in a future release
   (me).

 - Improve the cancel hash locking (Hao)

 - kbuf cleanups (Hao)

 - Efficiency improvements to the task_work handling (Dylan, Pavel)

 - Provided buffer improvements (Dylan)

 - Add support for recv/recvmsg multishot support. This is similar to
   the accept (or poll) support for have for multishot, where a single
   SQE can trigger everytime data is received. For applications that
   expect to do more than a few receives on an instantiated socket, this
   greatly improves efficiency (Dylan).

 - Efficiency improvements for poll handling (Pavel)

 - Poll cancelation improvements (Pavel)

 - Allow specifiying a range for direct descriptor allocations (Pavel)

 - Cleanup the cqe32 handling (Pavel)

 - Move io_uring types to greatly cleanup the tracing (Pavel)

 - Tons of great code cleanups and improvements (Pavel)

 - Add a way to do sync cancelations rather than through the sqe -> cqe
   interface, as that's a lot easier to use for some use cases (me).

 - Add support to IORING_OP_MSG_RING for sending direct descriptors to a
   different ring. This avoids the usually problematic SCM case, as we
   disallow those. (me)

 - Make the per-command alloc cache we use for apoll generic, place
   limits on it, and use it for netmsg as well (me).

 - Various cleanups (me, Michal, Gustavo, Uros)

* tag 'for-5.20/io_uring-2022-07-29' of git://git.kernel.dk/linux-block: (172 commits)
  io_uring: ensure REQ_F_ISREG is set async offload
  net: fix compat pointer in get_compat_msghdr()
  io_uring: Don't require reinitable percpu_ref
  io_uring: fix types in io_recvmsg_multishot_overflow
  io_uring: Use atomic_long_try_cmpxchg in __io_account_mem
  io_uring: support multishot in recvmsg
  net: copy from user before calling __get_compat_msghdr
  net: copy from user before calling __copy_msghdr
  io_uring: support 0 length iov in buffer select in compat
  io_uring: fix multishot ending when not polled
  io_uring: add netmsg cache
  io_uring: impose max limit on apoll cache
  io_uring: add abstraction around apoll cache
  io_uring: move apoll cache to poll.c
  io_uring: consolidate hash_locked io-wq handling
  io_uring: clear REQ_F_HASH_LOCKED on hash removal
  io_uring: don't race double poll setting REQ_F_ASYNC_DATA
  io_uring: don't miss setting REQ_F_DOUBLE_POLL
  io_uring: disable multishot recvmsg
  io_uring: only trace one of complete or overflow
  ...
2022-08-02 13:20:44 -07:00
Linus Torvalds
b167fdffe9 This cycle's scheduler updates for v6.0 are:
Load-balancing improvements:
 ============================
 
 - Improve NUMA balancing on AMD Zen systems for affine workloads.
 
 - Improve the handling of reduced-capacity CPUs in load-balancing.
 
 - Energy Model improvements: fix & refine all the energy fairness metrics (PELT),
   and remove the conservative threshold requiring 6% energy savings to
   migrate a task. Doing this improves power efficiency for most workloads,
   and also increases the reliability of energy-efficiency scheduling.
 
 - Optimize/tweak select_idle_cpu() to spend (much) less time searching
   for an idle CPU on overloaded systems. There's reports of several
   milliseconds spent there on large systems with large workloads ...
 
   [ Since the search logic changed, there might be behavioral side effects. ]
 
 - Improve NUMA imbalance behavior. On certain systems
   with spare capacity, initial placement of tasks is non-deterministic,
   and such an artificial placement imbalance can persist for a long time,
   hurting (and sometimes helping) performance.
 
   The fix is to make fork-time task placement consistent with runtime
   NUMA balancing placement.
 
   Note that some performance regressions were reported against this,
   caused by workloads that are not memory bandwith limited, which benefit
   from the artificial locality of the placement bug(s). Mel Gorman's
   conclusion, with which we concur, was that consistency is better than
   random workload benefits from non-deterministic bugs:
 
      "Given there is no crystal ball and it's a tradeoff, I think it's
       better to be consistent and use similar logic at both fork time
       and runtime even if it doesn't have universal benefit."
 
 - Improve core scheduling by fixing a bug in sched_core_update_cookie() that
   caused unnecessary forced idling.
 
 - Improve wakeup-balancing by allowing same-LLC wakeup of idle CPUs for newly
   woken tasks.
 
 - Fix a newidle balancing bug that introduced unnecessary wakeup latencies.
 
 ABI improvements/fixes:
 =======================
 
 - Do not check capabilities and do not issue capability check denial messages
   when a scheduler syscall doesn't require privileges. (Such as increasing niceness.)
 
 - Add forced-idle accounting to cgroups too.
 
 - Fix/improve the RSEQ ABI to not just silently accept unknown flags.
   (No existing tooling is known to have learned to rely on the previous behavior.)
 
 - Depreciate the (unused) RSEQ_CS_FLAG_NO_RESTART_ON_* flags.
 
 Optimizations:
 ==============
 
 - Optimize & simplify leaf_cfs_rq_list()
 
 - Micro-optimize set_nr_{and_not,if}_polling() via try_cmpxchg().
 
 Misc fixes & cleanups:
 ======================
 
 - Fix the RSEQ self-tests on RISC-V and Glibc 2.35 systems.
 
 - Fix a full-NOHZ bug that can in some cases result in the tick not being
   re-enabled when the last SCHED_RT task is gone from a runqueue but there's
   still SCHED_OTHER tasks around.
 
 - Various PREEMPT_RT related fixes.
 
 - Misc cleanups & smaller fixes.
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-core-2022-08-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler updates from Ingo Molnar:
"Load-balancing improvements:

   - Improve NUMA balancing on AMD Zen systems for affine workloads.

   - Improve the handling of reduced-capacity CPUs in load-balancing.

   - Energy Model improvements: fix & refine all the energy fairness
     metrics (PELT), and remove the conservative threshold requiring 6%
     energy savings to migrate a task. Doing this improves power
     efficiency for most workloads, and also increases the reliability
     of energy-efficiency scheduling.

   - Optimize/tweak select_idle_cpu() to spend (much) less time
     searching for an idle CPU on overloaded systems. There's reports of
     several milliseconds spent there on large systems with large
     workloads ...

     [ Since the search logic changed, there might be behavioral side
       effects. ]

   - Improve NUMA imbalance behavior. On certain systems with spare
     capacity, initial placement of tasks is non-deterministic, and such
     an artificial placement imbalance can persist for a long time,
     hurting (and sometimes helping) performance.

     The fix is to make fork-time task placement consistent with runtime
     NUMA balancing placement.

     Note that some performance regressions were reported against this,
     caused by workloads that are not memory bandwith limited, which
     benefit from the artificial locality of the placement bug(s). Mel
     Gorman's conclusion, with which we concur, was that consistency is
     better than random workload benefits from non-deterministic bugs:

        "Given there is no crystal ball and it's a tradeoff, I think
         it's better to be consistent and use similar logic at both fork
         time and runtime even if it doesn't have universal benefit."

   - Improve core scheduling by fixing a bug in
     sched_core_update_cookie() that caused unnecessary forced idling.

   - Improve wakeup-balancing by allowing same-LLC wakeup of idle CPUs
     for newly woken tasks.

   - Fix a newidle balancing bug that introduced unnecessary wakeup
     latencies.

  ABI improvements/fixes:

   - Do not check capabilities and do not issue capability check denial
     messages when a scheduler syscall doesn't require privileges. (Such
     as increasing niceness.)

   - Add forced-idle accounting to cgroups too.

   - Fix/improve the RSEQ ABI to not just silently accept unknown flags.
     (No existing tooling is known to have learned to rely on the
     previous behavior.)

   - Depreciate the (unused) RSEQ_CS_FLAG_NO_RESTART_ON_* flags.

  Optimizations:

   - Optimize & simplify leaf_cfs_rq_list()

   - Micro-optimize set_nr_{and_not,if}_polling() via try_cmpxchg().

  Misc fixes & cleanups:

   - Fix the RSEQ self-tests on RISC-V and Glibc 2.35 systems.

   - Fix a full-NOHZ bug that can in some cases result in the tick not
     being re-enabled when the last SCHED_RT task is gone from a
     runqueue but there's still SCHED_OTHER tasks around.

   - Various PREEMPT_RT related fixes.

   - Misc cleanups & smaller fixes"

* tag 'sched-core-2022-08-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (32 commits)
  rseq: Kill process when unknown flags are encountered in ABI structures
  rseq: Deprecate RSEQ_CS_FLAG_NO_RESTART_ON_* flags
  sched/core: Fix the bug that task won't enqueue into core tree when update cookie
  nohz/full, sched/rt: Fix missed tick-reenabling bug in dequeue_task_rt()
  sched/core: Always flush pending blk_plug
  sched/fair: fix case with reduced capacity CPU
  sched/core: Use try_cmpxchg in set_nr_{and_not,if}_polling
  sched/core: add forced idle accounting for cgroups
  sched/fair: Remove the energy margin in feec()
  sched/fair: Remove task_util from effective utilization in feec()
  sched/fair: Use the same cpumask per-PD throughout find_energy_efficient_cpu()
  sched/fair: Rename select_idle_mask to select_rq_mask
  sched, drivers: Remove max param from effective_cpu_util()/sched_cpu_util()
  sched/fair: Decay task PELT values during wakeup migration
  sched/fair: Provide u64 read for 32-bits arch helper
  sched/fair: Introduce SIS_UTIL to search idle CPU based on sum of util_avg
  sched: only perform capability check on privileged operation
  sched: Remove unused function group_first_cpu()
  sched/fair: Remove redundant word " *"
  selftests/rseq: check if libc rseq support is registered
  ...
2022-08-01 11:49:06 -07:00
Jens Axboe
ed29b0b4fd io_uring: move to separate directory
In preparation for splitting io_uring up a bit, move it into its own
top level directory. It didn't really belong in fs/ anyway, as it's
not a file system only API.

This adds io_uring/ and moves the core files in there, and updates the
MAINTAINERS file for the new location.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-07-24 18:39:10 -06:00
Paul E. McKenney
34bc7b454d Merge branch 'ctxt.2022.07.05a' into HEAD
ctxt.2022.07.05a: Linux-kernel memory model development branch.
2022-07-21 17:46:18 -07:00
John Keeping
401e4963bf sched/core: Always flush pending blk_plug
With CONFIG_PREEMPT_RT, it is possible to hit a deadlock between two
normal priority tasks (SCHED_OTHER, nice level zero):

	INFO: task kworker/u8:0:8 blocked for more than 491 seconds.
	      Not tainted 5.15.49-rt46 #1
	"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
	task:kworker/u8:0    state:D stack:    0 pid:    8 ppid:     2 flags:0x00000000
	Workqueue: writeback wb_workfn (flush-7:0)
	[<c08a3a10>] (__schedule) from [<c08a3d84>] (schedule+0xdc/0x134)
	[<c08a3d84>] (schedule) from [<c08a65a0>] (rt_mutex_slowlock_block.constprop.0+0xb8/0x174)
	[<c08a65a0>] (rt_mutex_slowlock_block.constprop.0) from [<c08a6708>]
	+(rt_mutex_slowlock.constprop.0+0xac/0x174)
	[<c08a6708>] (rt_mutex_slowlock.constprop.0) from [<c0374d60>] (fat_write_inode+0x34/0x54)
	[<c0374d60>] (fat_write_inode) from [<c0297304>] (__writeback_single_inode+0x354/0x3ec)
	[<c0297304>] (__writeback_single_inode) from [<c0297998>] (writeback_sb_inodes+0x250/0x45c)
	[<c0297998>] (writeback_sb_inodes) from [<c0297c20>] (__writeback_inodes_wb+0x7c/0xb8)
	[<c0297c20>] (__writeback_inodes_wb) from [<c0297f24>] (wb_writeback+0x2c8/0x2e4)
	[<c0297f24>] (wb_writeback) from [<c0298c40>] (wb_workfn+0x1a4/0x3e4)
	[<c0298c40>] (wb_workfn) from [<c0138ab8>] (process_one_work+0x1fc/0x32c)
	[<c0138ab8>] (process_one_work) from [<c0139120>] (worker_thread+0x22c/0x2d8)
	[<c0139120>] (worker_thread) from [<c013e6e0>] (kthread+0x16c/0x178)
	[<c013e6e0>] (kthread) from [<c01000fc>] (ret_from_fork+0x14/0x38)
	Exception stack(0xc10e3fb0 to 0xc10e3ff8)
	3fa0:                                     00000000 00000000 00000000 00000000
	3fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
	3fe0: 00000000 00000000 00000000 00000000 00000013 00000000

	INFO: task tar:2083 blocked for more than 491 seconds.
	      Not tainted 5.15.49-rt46 #1
	"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
	task:tar             state:D stack:    0 pid: 2083 ppid:  2082 flags:0x00000000
	[<c08a3a10>] (__schedule) from [<c08a3d84>] (schedule+0xdc/0x134)
	[<c08a3d84>] (schedule) from [<c08a41b0>] (io_schedule+0x14/0x24)
	[<c08a41b0>] (io_schedule) from [<c08a455c>] (bit_wait_io+0xc/0x30)
	[<c08a455c>] (bit_wait_io) from [<c08a441c>] (__wait_on_bit_lock+0x54/0xa8)
	[<c08a441c>] (__wait_on_bit_lock) from [<c08a44f4>] (out_of_line_wait_on_bit_lock+0x84/0xb0)
	[<c08a44f4>] (out_of_line_wait_on_bit_lock) from [<c0371fb0>] (fat_mirror_bhs+0xa0/0x144)
	[<c0371fb0>] (fat_mirror_bhs) from [<c0372a68>] (fat_alloc_clusters+0x138/0x2a4)
	[<c0372a68>] (fat_alloc_clusters) from [<c0370b14>] (fat_alloc_new_dir+0x34/0x250)
	[<c0370b14>] (fat_alloc_new_dir) from [<c03787c0>] (vfat_mkdir+0x58/0x148)
	[<c03787c0>] (vfat_mkdir) from [<c0277b60>] (vfs_mkdir+0x68/0x98)
	[<c0277b60>] (vfs_mkdir) from [<c027b484>] (do_mkdirat+0xb0/0xec)
	[<c027b484>] (do_mkdirat) from [<c0100060>] (ret_fast_syscall+0x0/0x1c)
	Exception stack(0xc2e1bfa8 to 0xc2e1bff0)
	bfa0:                   01ee42f0 01ee4208 01ee42f0 000041ed 00000000 00004000
	bfc0: 01ee42f0 01ee4208 00000000 00000027 01ee4302 00000004 000dcb00 01ee4190
	bfe0: 000dc368 bed11924 0006d4b0 b6ebddfc

Here the kworker is waiting on msdos_sb_info::s_lock which is held by
tar which is in turn waiting for a buffer which is locked waiting to be
flushed, but this operation is plugged in the kworker.

The lock is a normal struct mutex, so tsk_is_pi_blocked() will always
return false on !RT and thus the behaviour changes for RT.

It seems that the intent here is to skip blk_flush_plug() in the case
where a non-preemptible lock (such as a spinlock) has been converted to
a rtmutex on RT, which is the case covered by the SM_RTLOCK_WAIT
schedule flag.  But sched_submit_work() is only called from schedule()
which is never called in this scenario, so the check can simply be
deleted.

Looking at the history of the -rt patchset, in fact this change was
present from v5.9.1-rt20 until being dropped in v5.13-rt1 as it was part
of a larger patch [1] most of which was replaced by commit b4bfa3fcfe
("sched/core: Rework the __schedule() preempt argument").

As described in [1]:

   The schedule process must distinguish between blocking on a regular
   sleeping lock (rwsem and mutex) and a RT-only sleeping lock (spinlock
   and rwlock):
   - rwsem and mutex must flush block requests (blk_schedule_flush_plug())
     even if blocked on a lock. This can not deadlock because this also
     happens for non-RT.
     There should be a warning if the scheduling point is within a RCU read
     section.

   - spinlock and rwlock must not flush block requests. This will deadlock
     if the callback attempts to acquire a lock which is already acquired.
     Similarly to being preempted, there should be no warning if the
     scheduling point is within a RCU read section.

and with the tsk_is_pi_blocked() in the scheduler path, we hit the first
issue.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git/tree/patches/0022-locking-rtmutex-Use-custom-scheduling-function-for-s.patch?h=linux-5.10.y-rt-patches

Signed-off-by: John Keeping <john@metanate.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lkml.kernel.org/r/20220708162702.1758865-1-john@metanate.com
2022-07-13 11:29:17 +02:00
Uros Bizjak
c02d5546ea sched/core: Use try_cmpxchg in set_nr_{and_not,if}_polling
Use try_cmpxchg instead of cmpxchg (*ptr, old, new) != old in
set_nr_{and_not,if}_polling. x86 cmpxchg returns success in ZF flag,
so this change saves a compare after cmpxchg.

The definition of cmpxchg based fetch_or was changed in the
same way as atomic_fetch_##op definitions were changed
in e6790e4b5d.

Also declare these two functions as inline to ensure inlining. In the
case of set_nr_and_not_polling, the compiler (gcc) tries to outsmart
itself by constructing the boolean return value with logic operations
on the fetched value, and these extra operations enlarge the function
over the inlining threshold value.

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220629151552.6015-1-ubizjak@gmail.com
2022-07-04 09:23:08 +02:00
Frederic Weisbecker
24a9c54182 context_tracking: Split user tracking Kconfig
Context tracking is going to be used not only to track user transitions
but also idle/IRQs/NMIs. The user tracking part will then become a
separate feature. Prepare Kconfig for that.

[ frederic: Apply Max Filippov feedback. ]

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Uladzislau Rezki <uladzislau.rezki@sony.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Nicolas Saenz Julienne <nsaenz@kernel.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Cc: Yu Liao <liaoyu15@huawei.com>
Cc: Phil Auld <pauld@redhat.com>
Cc: Paul Gortmaker<paul.gortmaker@windriver.com>
Cc: Alex Belits <abelits@marvell.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Tested-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
2022-06-29 17:04:09 -07:00
Dietmar Eggemann
ec4fc801a0 sched/fair: Rename select_idle_mask to select_rq_mask
On 21/06/2022 11:04, Vincent Donnefort wrote:
> From: Dietmar Eggemann <dietmar.eggemann@arm.com>

https://lkml.kernel.org/r/202206221253.ZVyGQvPX-lkp@intel.com discovered
that this patch doesn't build anymore (on tip sched/core or linux-next)
because of commit f5b2eeb499 ("sched/fair: Consider CPU affinity when
allowing NUMA imbalance in find_idlest_group()").

New version of [PATCH v11 4/7] sched/fair: Rename select_idle_mask to
select_rq_mask below.

-- >8 --

Decouple the name of the per-cpu cpumask select_idle_mask from its usage
in select_idle_[cpu/capacity]() of the CFS run-queue selection
(select_task_rq_fair()).

This is to support the reuse of this cpumask in the Energy Aware
Scheduling (EAS) path (find_energy_efficient_cpu()) of the CFS run-queue
selection.

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>
Tested-by: Lukasz Luba <lukasz.luba@arm.com>
Link: https://lkml.kernel.org/r/250691c7-0e2b-05ab-bedf-b245c11d9400@arm.com
2022-06-28 09:17:47 +02:00
Dietmar Eggemann
bb44799949 sched, drivers: Remove max param from effective_cpu_util()/sched_cpu_util()
effective_cpu_util() already has a `int cpu' parameter which allows to
retrieve the CPU capacity scale factor (or maximum CPU capacity) inside
this function via an arch_scale_cpu_capacity(cpu).

A lot of code calling effective_cpu_util() (or the shim
sched_cpu_util()) needs the maximum CPU capacity, i.e. it will call
arch_scale_cpu_capacity() already.
But not having to pass it into effective_cpu_util() will make the EAS
wake-up code easier, especially when the maximum CPU capacity reduced
by the thermal pressure is passed through the EAS wake-up functions.

Due to the asymmetric CPU capacity support of arm/arm64 architectures,
arch_scale_cpu_capacity(int cpu) is a per-CPU variable read access via
per_cpu(cpu_scale, cpu) on such a system.
On all other architectures it is a a compile-time constant
(SCHED_CAPACITY_SCALE).

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Vincent Guittot <vincent.guittot@linaro.org>
Tested-by: Lukasz Luba <lukasz.luba@arm.com>
Link: https://lkml.kernel.org/r/20220621090414.433602-4-vdonnefort@google.com
2022-06-28 09:17:46 +02:00
Christian Göttsche
700a78335f sched: only perform capability check on privileged operation
sched_setattr(2) issues via kernel/sched/core.c:__sched_setscheduler()
a CAP_SYS_NICE audit event unconditionally, even when the requested
operation does not require that capability / is unprivileged, i.e. for
reducing niceness.
This is relevant in connection with SELinux, where a capability check
results in a policy decision and by default a denial message on
insufficient permission is issued.
It can lead to three undesired cases:
  1. A denial message is generated, even in case the operation was an
     unprivileged one and thus the syscall succeeded, creating noise.
  2. To avoid the noise from 1. the policy writer adds a rule to ignore
     those denial messages, hiding future syscalls, where the task
     performs an actual privileged operation, leading to hidden limited
     functionality of that task.
  3. To avoid the noise from 1. the policy writer adds a rule to allow
     the task the capability CAP_SYS_NICE, while it does not need it,
     violating the principle of least privilege.

Conduct privilged/unprivileged categorization first and perform a
capable test (and at most once) only if needed.

Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220615152505.310488-1-cgzones@googlemail.com
2022-06-28 09:08:29 +02:00
Paul E. McKenney
e386b67257 rcu-tasks: Eliminate RCU Tasks Trace IPIs to online CPUs
Currently, the RCU Tasks Trace grace-period kthread IPIs each online CPU
using smp_call_function_single() in order to track any tasks currently in
RCU Tasks Trace read-side critical sections during which the corresponding
task has neither blocked nor been preempted.  These IPIs are annoying
and are also not strictly necessary because any task that blocks or is
preempted within its current RCU Tasks Trace read-side critical section
will be tracked on one of the per-CPU rcu_tasks_percpu structure's
->rtp_blkd_tasks list.  So the only time that this is a problem is if
one of the CPUs runs through a long-duration RCU Tasks Trace read-side
critical section without a context switch.

Note that the task_call_func() function cannot help here because there is
no safe way to identify the target task.  Of course, the task_call_func()
function will be very useful later, when processing the list of tasks,
but it needs to know the task.

This commit therefore creates a cpu_curr_snapshot() function that returns
a pointer the task_struct structure of some task that happened to be
running on the specified CPU more or less during the time that the
cpu_curr_snapshot() function was executing.  If there was no context
switch during this time, this function will return a pointer to the
task_struct structure of the task that was running throughout.  If there
was a context switch, then the outgoing task will be taken care of by
RCU's context-switch hook, and the incoming task was either already taken
care during some previous context switch, or it is not currently within an
RCU Tasks Trace read-side critical section.  And in this latter case, the
grace period already started, so there is no need to wait on this task.

This new cpu_curr_snapshot() function is invoked on each CPU early in
the RCU Tasks Trace grace-period processing, and the resulting tasks
are queued for later quiescent-state inspection.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: KP Singh <kpsingh@kernel.org>
2022-06-21 15:49:38 -07:00
Tianchen Ding
f3dd3f6745 sched: Remove the limitation of WF_ON_CPU on wakelist if wakee cpu is idle
Wakelist can help avoid cache bouncing and offload the overhead of waker
cpu. So far, using wakelist within the same llc only happens on
WF_ON_CPU, and this limitation could be removed to further improve
wakeup performance.

The commit 518cd62341 ("sched: Only queue remote wakeups when
crossing cache boundaries") disabled queuing tasks on wakelist when
the cpus share llc. This is because, at that time, the scheduler must
send IPIs to do ttwu_queue_wakelist. Nowadays, ttwu_queue_wakelist also
supports TIF_POLLING, so this is not a problem now when the wakee cpu is
in idle polling.

Benefits:
  Queuing the task on idle cpu can help improving performance on waker cpu
  and utilization on wakee cpu, and further improve locality because
  the wakee cpu can handle its own rq. This patch helps improving rt on
  our real java workloads where wakeup happens frequently.

  Consider the normal condition (CPU0 and CPU1 share same llc)
  Before this patch:

         CPU0                                       CPU1

    select_task_rq()                                idle
    rq_lock(CPU1->rq)
    enqueue_task(CPU1->rq)
    notify CPU1 (by sending IPI or CPU1 polling)

                                                    resched()

  After this patch:

         CPU0                                       CPU1

    select_task_rq()                                idle
    add to wakelist of CPU1
    notify CPU1 (by sending IPI or CPU1 polling)

                                                    rq_lock(CPU1->rq)
                                                    enqueue_task(CPU1->rq)
                                                    resched()

  We see CPU0 can finish its work earlier. It only needs to put task to
  wakelist and return.
  While CPU1 is idle, so let itself handle its own runqueue data.

This patch brings no difference about IPI.
  This patch only takes effect when the wakee cpu is:
  1) idle polling
  2) idle not polling

  For 1), there will be no IPI with or without this patch.

  For 2), there will always be an IPI before or after this patch.
  Before this patch: waker cpu will enqueue task and check preempt. Since
  "idle" will be sure to be preempted, waker cpu must send a resched IPI.
  After this patch: waker cpu will put the task to the wakelist of wakee
  cpu, and send an IPI.

Benchmark:
We've tested schbench, unixbench, and hachbench on both x86 and arm64.

On x86 (Intel Xeon Platinum 8269CY):
  schbench -m 2 -t 8

    Latency percentiles (usec)              before        after
        50.0000th:                             8            6
        75.0000th:                            10            7
        90.0000th:                            11            8
        95.0000th:                            12            8
        *99.0000th:                           13           10
        99.5000th:                            15           11
        99.9000th:                            18           14

  Unixbench with full threads (104)
                                            before        after
    Dhrystone 2 using register variables  3011862938    3009935994  -0.06%
    Double-Precision Whetstone              617119.3      617298.5   0.03%
    Execl Throughput                         27667.3       27627.3  -0.14%
    File Copy 1024 bufsize 2000 maxblocks   785871.4      784906.2  -0.12%
    File Copy 256 bufsize 500 maxblocks     210113.6      212635.4   1.20%
    File Copy 4096 bufsize 8000 maxblocks  2328862.2     2320529.1  -0.36%
    Pipe Throughput                      145535622.8   145323033.2  -0.15%
    Pipe-based Context Switching           3221686.4     3583975.4  11.25%
    Process Creation                        101347.1      103345.4   1.97%
    Shell Scripts (1 concurrent)            120193.5      123977.8   3.15%
    Shell Scripts (8 concurrent)             17233.4       17138.4  -0.55%
    System Call Overhead                   5300604.8     5312213.6   0.22%

  hackbench -g 1 -l 100000
                                            before        after
    Time                                     3.246        2.251

On arm64 (Ampere Altra):
  schbench -m 2 -t 8

    Latency percentiles (usec)              before        after
        50.0000th:                            14           10
        75.0000th:                            19           14
        90.0000th:                            22           16
        95.0000th:                            23           16
        *99.0000th:                           24           17
        99.5000th:                            24           17
        99.9000th:                            28           25

  Unixbench with full threads (80)
                                            before        after
    Dhrystone 2 using register variables  3536194249    3537019613   0.02%
    Double-Precision Whetstone              629383.6      629431.6   0.01%
    Execl Throughput                         65920.5       65846.2  -0.11%
    File Copy 1024 bufsize 2000 maxblocks  1063722.8     1064026.8   0.03%
    File Copy 256 bufsize 500 maxblocks     322684.5      318724.5  -1.23%
    File Copy 4096 bufsize 8000 maxblocks  2348285.3     2328804.8  -0.83%
    Pipe Throughput                      133542875.3   131619389.8  -1.44%
    Pipe-based Context Switching           3215356.1     3576945.1  11.25%
    Process Creation                        108520.5      120184.6  10.75%
    Shell Scripts (1 concurrent)            122636.3        121888  -0.61%
    Shell Scripts (8 concurrent)             17462.1       17381.4  -0.46%
    System Call Overhead                   4429998.9     4435006.7   0.11%

  hackbench -g 1 -l 100000
                                            before        after
    Time                                     4.217        2.916

Our patch has improvement on schbench, hackbench
and Pipe-based Context Switching of unixbench
when there exists idle cpus,
and no obvious regression on other tests of unixbench.
This can help improve rt in scenes where wakeup happens frequently.

Signed-off-by: Tianchen Ding <dtcccc@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Link: https://lore.kernel.org/r/20220608233412.327341-3-dtcccc@linux.alibaba.com
2022-06-13 10:30:01 +02:00
Tianchen Ding
28156108fe sched: Fix the check of nr_running at queue wakelist
The commit 2ebb177175 ("sched/core: Offload wakee task activation if it
the wakee is descheduling") checked rq->nr_running <= 1 to avoid task
stacking when WF_ON_CPU.

Per the ordering of writes to p->on_rq and p->on_cpu, observing p->on_cpu
(WF_ON_CPU) in ttwu_queue_cond() implies !p->on_rq, IOW p has gone through
the deactivate_task() in __schedule(), thus p has been accounted out of
rq->nr_running. As such, the task being the only runnable task on the rq
implies reading rq->nr_running == 0 at that point.

The benchmark result is in [1].

[1] https://lore.kernel.org/all/e34de686-4e85-bde1-9f3c-9bbc86b38627@linux.alibaba.com/

Suggested-by: Valentin Schneider <vschneid@redhat.com>
Signed-off-by: Tianchen Ding <dtcccc@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Link: https://lore.kernel.org/r/20220608233412.327341-2-dtcccc@linux.alibaba.com
2022-06-13 10:30:01 +02:00
Peter Zijlstra
04193d590b sched: Fix balance_push() vs __sched_setscheduler()
The purpose of balance_push() is to act as a filter on task selection
in the case of CPU hotplug, specifically when taking the CPU out.

It does this by (ab)using the balance callback infrastructure, with
the express purpose of keeping all the unlikely/odd cases in a single
place.

In order to serve its purpose, the balance_push_callback needs to be
(exclusively) on the callback list at all times (noting that the
callback always places itself back on the list the moment it runs,
also noting that when the CPU goes down, regular balancing concerns
are moot, so ignoring them is fine).

And here-in lies the problem, __sched_setscheduler()'s use of
splice_balance_callbacks() takes the callbacks off the list across a
lock-break, making it possible for, an interleaving, __schedule() to
see an empty list and not get filtered.

Fixes: ae79270232 ("sched: Optimize finish_lock_switch()")
Reported-by: Jing-Ting Wu <jing-ting.wu@mediatek.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Jing-Ting Wu <jing-ting.wu@mediatek.com>
Link: https://lkml.kernel.org/r/20220519134706.GH2578@worktop.programming.kicks-ass.net
2022-06-13 10:15:07 +02:00
Linus Torvalds
67850b7bdc While looking at the ptrace problems with PREEMPT_RT and the problems
of Peter Zijlstra was encountering with ptrace in his freezer rewrite
 I identified some cleanups to ptrace_stop that make sense on their own
 and move make resolving the other problems much simpler.
 
 The biggest issue is the habbit of the ptrace code to change task->__state
 from the tracer to suppress TASK_WAKEKILL from waking up the tracee.  No
 other code in the kernel does that and it is straight forward to update
 signal_wake_up and friends to make that unnecessary.
 
 Peter's task freezer sets frozen tasks to a new state TASK_FROZEN and
 then it stores them by calling "wake_up_state(t, TASK_FROZEN)" relying
 on the fact that all stopped states except the special stop states can
 tolerate spurious wake up and recover their state.
 
 The state of stopped and traced tasked is changed to be stored in
 task->jobctl as well as in task->__state.  This makes it possible for
 the freezer to recover tasks in these special states, as well as
 serving as a general cleanup.  With a little more work in that
 direction I believe TASK_STOPPED can learn to tolerate spurious wake
 ups and become an ordinary stop state.
 
 The TASK_TRACED state has to remain a special state as the registers for
 a process are only reliably available when the process is stopped in
 the scheduler.  Fundamentally ptrace needs acess to the saved
 register values of a task.
 
 There are bunch of semi-random ptrace related cleanups that were found
 while looking at these issues.
 
 One cleanup that deserves to be called out is from commit 57b6de08b5
 ("ptrace: Admit ptrace_stop can generate spuriuos SIGTRAPs").  This
 makes a change that is technically user space visible, in the handling
 of what happens to a tracee when a tracer dies unexpectedly.
 According to our testing and our understanding of userspace nothing
 cares that spurious SIGTRAPs can be generated in that case.
 
 The entire discussion can be found at:
   https://lkml.kernel.org/r/87a6bv6dl6.fsf_-_@email.froward.int.ebiederm.org
 
 Eric W. Biederman (11):
       signal: Rename send_signal send_signal_locked
       signal: Replace __group_send_sig_info with send_signal_locked
       ptrace/um: Replace PT_DTRACE with TIF_SINGLESTEP
       ptrace/xtensa: Replace PT_SINGLESTEP with TIF_SINGLESTEP
       ptrace: Remove arch_ptrace_attach
       signal: Use lockdep_assert_held instead of assert_spin_locked
       ptrace: Reimplement PTRACE_KILL by always sending SIGKILL
       ptrace: Document that wait_task_inactive can't fail
       ptrace: Admit ptrace_stop can generate spuriuos SIGTRAPs
       ptrace: Don't change __state
       ptrace: Always take siglock in ptrace_resume
 
 Peter Zijlstra (1):
       sched,signal,ptrace: Rework TASK_TRACED, TASK_STOPPED state
 
  arch/ia64/include/asm/ptrace.h    |   4 --
  arch/ia64/kernel/ptrace.c         |  57 ----------------
  arch/um/include/asm/thread_info.h |   2 +
  arch/um/kernel/exec.c             |   2 +-
  arch/um/kernel/process.c          |   2 +-
  arch/um/kernel/ptrace.c           |   8 +--
  arch/um/kernel/signal.c           |   4 +-
  arch/x86/kernel/step.c            |   3 +-
  arch/xtensa/kernel/ptrace.c       |   4 +-
  arch/xtensa/kernel/signal.c       |   4 +-
  drivers/tty/tty_jobctrl.c         |   4 +-
  include/linux/ptrace.h            |   7 --
  include/linux/sched.h             |  10 ++-
  include/linux/sched/jobctl.h      |   8 +++
  include/linux/sched/signal.h      |  20 ++++--
  include/linux/signal.h            |   3 +-
  kernel/ptrace.c                   |  87 ++++++++---------------
  kernel/sched/core.c               |   5 +-
  kernel/signal.c                   | 140 +++++++++++++++++---------------------
  kernel/time/posix-cpu-timers.c    |   6 +-
  20 files changed, 140 insertions(+), 240 deletions(-)
 
 Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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Merge tag 'ptrace_stop-cleanup-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

Pull ptrace_stop cleanups from Eric Biederman:
 "While looking at the ptrace problems with PREEMPT_RT and the problems
  Peter Zijlstra was encountering with ptrace in his freezer rewrite I
  identified some cleanups to ptrace_stop that make sense on their own
  and move make resolving the other problems much simpler.

  The biggest issue is the habit of the ptrace code to change
  task->__state from the tracer to suppress TASK_WAKEKILL from waking up
  the tracee. No other code in the kernel does that and it is straight
  forward to update signal_wake_up and friends to make that unnecessary.

  Peter's task freezer sets frozen tasks to a new state TASK_FROZEN and
  then it stores them by calling "wake_up_state(t, TASK_FROZEN)" relying
  on the fact that all stopped states except the special stop states can
  tolerate spurious wake up and recover their state.

  The state of stopped and traced tasked is changed to be stored in
  task->jobctl as well as in task->__state. This makes it possible for
  the freezer to recover tasks in these special states, as well as
  serving as a general cleanup. With a little more work in that
  direction I believe TASK_STOPPED can learn to tolerate spurious wake
  ups and become an ordinary stop state.

  The TASK_TRACED state has to remain a special state as the registers
  for a process are only reliably available when the process is stopped
  in the scheduler. Fundamentally ptrace needs acess to the saved
  register values of a task.

  There are bunch of semi-random ptrace related cleanups that were found
  while looking at these issues.

  One cleanup that deserves to be called out is from commit 57b6de08b5
  ("ptrace: Admit ptrace_stop can generate spuriuos SIGTRAPs"). This
  makes a change that is technically user space visible, in the handling
  of what happens to a tracee when a tracer dies unexpectedly. According
  to our testing and our understanding of userspace nothing cares that
  spurious SIGTRAPs can be generated in that case"

* tag 'ptrace_stop-cleanup-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  sched,signal,ptrace: Rework TASK_TRACED, TASK_STOPPED state
  ptrace: Always take siglock in ptrace_resume
  ptrace: Don't change __state
  ptrace: Admit ptrace_stop can generate spuriuos SIGTRAPs
  ptrace: Document that wait_task_inactive can't fail
  ptrace: Reimplement PTRACE_KILL by always sending SIGKILL
  signal: Use lockdep_assert_held instead of assert_spin_locked
  ptrace: Remove arch_ptrace_attach
  ptrace/xtensa: Replace PT_SINGLESTEP with TIF_SINGLESTEP
  ptrace/um: Replace PT_DTRACE with TIF_SINGLESTEP
  signal: Replace __group_send_sig_info with send_signal_locked
  signal: Rename send_signal send_signal_locked
2022-06-03 16:13:25 -07:00
Linus Torvalds
44d35720c9 sysctl changes for v5.19-rc1
For two kernel releases now kernel/sysctl.c has been being cleaned up
 slowly, since the tables were grossly long, sprinkled with tons of #ifdefs and
 all this caused merge conflicts with one susbystem or another.
 
 This tree was put together to help try to avoid conflicts with these cleanups
 going on different trees at time. So nothing exciting on this pull request,
 just cleanups.
 
 I actually had this sysctl-next tree up since v5.18 but I missed sending a
 pull request for it on time during the last merge window. And so these changes
 have been being soaking up on sysctl-next and so linux-next for a while.
 The last change was merged May 4th.
 
 Most of the compile issues were reported by 0day and fixed.
 
 To help avoid a conflict with bpf folks at Daniel Borkmann's request
 I merged bpf-next/pr/bpf-sysctl into sysctl-next to get the effor which
 moves the BPF sysctls from kernel/sysctl.c to BPF core.
 
 Possible merge conflicts and known resolutions as per linux-next:
 
 bfp:
 https://lkml.kernel.org/r/20220414112812.652190b5@canb.auug.org.au
 
 rcu:
 https://lkml.kernel.org/r/20220420153746.4790d532@canb.auug.org.au
 
 powerpc:
 https://lkml.kernel.org/r/20220520154055.7f964b76@canb.auug.org.au
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Merge tag 'sysctl-5.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux

Pull sysctl updates from Luis Chamberlain:
 "For two kernel releases now kernel/sysctl.c has been being cleaned up
  slowly, since the tables were grossly long, sprinkled with tons of
  #ifdefs and all this caused merge conflicts with one susbystem or
  another.

  This tree was put together to help try to avoid conflicts with these
  cleanups going on different trees at time. So nothing exciting on this
  pull request, just cleanups.

  Thanks a lot to the Uniontech and Huawei folks for doing some of this
  nasty work"

* tag 'sysctl-5.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux: (28 commits)
  sched: Fix build warning without CONFIG_SYSCTL
  reboot: Fix build warning without CONFIG_SYSCTL
  kernel/kexec_core: move kexec_core sysctls into its own file
  sysctl: minor cleanup in new_dir()
  ftrace: fix building with SYSCTL=y but DYNAMIC_FTRACE=n
  fs/proc: Introduce list_for_each_table_entry for proc sysctl
  mm: fix unused variable kernel warning when SYSCTL=n
  latencytop: move sysctl to its own file
  ftrace: fix building with SYSCTL=n but DYNAMIC_FTRACE=y
  ftrace: Fix build warning
  ftrace: move sysctl_ftrace_enabled to ftrace.c
  kernel/do_mount_initrd: move real_root_dev sysctls to its own file
  kernel/delayacct: move delayacct sysctls to its own file
  kernel/acct: move acct sysctls to its own file
  kernel/panic: move panic sysctls to its own file
  kernel/lockdep: move lockdep sysctls to its own file
  mm: move page-writeback sysctls to their own file
  mm: move oom_kill sysctls to their own file
  kernel/reboot: move reboot sysctls to its own file
  sched: Move energy_aware sysctls to topology.c
  ...
2022-05-26 16:57:20 -07:00
Linus Torvalds
6f3f04c190 Scheduler changes in this cycle were:
- Updates to scheduler metrics:
 
     - PELT fixes & enhancements
     - PSI fixes & enhancements
     - Refactor cpu_util_without()
 
  - Updates to instrumentation/debugging:
 
     - Remove sched_trace_*() helper functions - can be done via debug info
     - Fix double update_rq_clock() warnings
 
  - Introduce & use "preemption model accessors" to simplify some of
    the Kconfig complexity.
 
  - Make softirq handling RT-safe.
 
  - Misc smaller fixes & cleanups.
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-core-2022-05-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler updates from Ingo Molnar:

 - Updates to scheduler metrics:
     - PELT fixes & enhancements
     - PSI fixes & enhancements
     - Refactor cpu_util_without()

 - Updates to instrumentation/debugging:
     - Remove sched_trace_*() helper functions - can be done via debug
       info
     - Fix double update_rq_clock() warnings

 - Introduce & use "preemption model accessors" to simplify some of the
   Kconfig complexity.

 - Make softirq handling RT-safe.

 - Misc smaller fixes & cleanups.

* tag 'sched-core-2022-05-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  topology: Remove unused cpu_cluster_mask()
  sched: Reverse sched_class layout
  sched/deadline: Remove superfluous rq clock update in push_dl_task()
  sched/core: Avoid obvious double update_rq_clock warning
  smp: Make softirq handling RT safe in flush_smp_call_function_queue()
  smp: Rename flush_smp_call_function_from_idle()
  sched: Fix missing prototype warnings
  sched/fair: Remove cfs_rq_tg_path()
  sched/fair: Remove sched_trace_*() helper functions
  sched/fair: Refactor cpu_util_without()
  sched/fair: Revise comment about lb decision matrix
  sched/psi: report zeroes for CPU full at the system level
  sched/fair: Delete useless condition in tg_unthrottle_up()
  sched/fair: Fix cfs_rq_clock_pelt() for throttled cfs_rq
  sched/fair: Move calculate of avg_load to a better location
  mailmap: Update my email address to @redhat.com
  MAINTAINERS: Add myself as scheduler topology reviewer
  psi: Fix trigger being fired unexpectedly at initial
  ftrace: Use preemption model accessors for trace header printout
  kcsan: Use preemption model accessors
2022-05-24 11:11:13 -07:00
Linus Torvalds
1e57930e9f RCU pull request for v5.19
This pull request contains the following branches:
 
 docs.2022.04.20a: Documentation updates.
 
 fixes.2022.04.20a: Miscellaneous fixes.
 
 nocb.2022.04.11b: Callback-offloading updates, mainly simplifications.
 
 rcu-tasks.2022.04.11b: RCU-tasks updates, including some -rt fixups,
 	handling of systems with sparse CPU numbering, and a fix for a
 	boot-time race-condition failure.
 
 srcu.2022.05.03a: Put SRCU on a memory diet in order to reduce the size
 	of the srcu_struct structure.
 
 torture.2022.04.11b: Torture-test updates fixing some bugs in tests and
 	closing some testing holes.
 
 torture-tasks.2022.04.20a: Torture-test updates for the RCU tasks flavors,
 	most notably ensuring that building rcutorture and friends does
 	not change the RCU-tasks-related Kconfig options.
 
 torturescript.2022.04.20a: Torture-test scripting updates.
 
 exp.2022.05.11a: Expedited grace-period updates, most notably providing
 	milliseconds-scale (not all that) soft real-time response from
 	synchronize_rcu_expedited().  This is also the first time in
 	almost 30 years of RCU that someone other than me has pushed
 	for a reduction in the RCU CPU stall-warning timeout, in this
 	case by more than three orders of magnitude from 21 seconds to
 	20 milliseconds.  This tighter timeout applies only to expedited
 	grace periods.
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Merge tag 'rcu.2022.05.19a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu

Pull RCU update from Paul McKenney:

 - Documentation updates

 - Miscellaneous fixes

 - Callback-offloading updates, mainly simplifications

 - RCU-tasks updates, including some -rt fixups, handling of systems
   with sparse CPU numbering, and a fix for a boot-time race-condition
   failure

 - Put SRCU on a memory diet in order to reduce the size of the
   srcu_struct structure

 - Torture-test updates fixing some bugs in tests and closing some
   testing holes

 - Torture-test updates for the RCU tasks flavors, most notably ensuring
   that building rcutorture and friends does not change the
   RCU-tasks-related Kconfig options

 - Torture-test scripting updates

 - Expedited grace-period updates, most notably providing
   milliseconds-scale (not all that) soft real-time response from
   synchronize_rcu_expedited().

   This is also the first time in almost 30 years of RCU that someone
   other than me has pushed for a reduction in the RCU CPU stall-warning
   timeout, in this case by more than three orders of magnitude from 21
   seconds to 20 milliseconds. This tighter timeout applies only to
   expedited grace periods

* tag 'rcu.2022.05.19a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu: (80 commits)
  rcu: Move expedited grace period (GP) work to RT kthread_worker
  rcu: Introduce CONFIG_RCU_EXP_CPU_STALL_TIMEOUT
  srcu: Drop needless initialization of sdp in srcu_gp_start()
  srcu: Prevent expedited GPs and blocking readers from consuming CPU
  srcu: Add contention check to call_srcu() srcu_data ->lock acquisition
  srcu: Automatically determine size-transition strategy at boot
  rcutorture: Make torture.sh allow for --kasan
  rcutorture: Make torture.sh refscale and rcuscale specify Tasks Trace RCU
  rcutorture: Make kvm.sh allow more memory for --kasan runs
  torture: Save "make allmodconfig" .config file
  scftorture: Remove extraneous "scf" from per_version_boot_params
  rcutorture: Adjust scenarios' Kconfig options for CONFIG_PREEMPT_DYNAMIC
  torture: Enable CSD-lock stall reports for scftorture
  torture: Skip vmlinux check for kvm-again.sh runs
  scftorture: Adjust for TASKS_RCU Kconfig option being selected
  rcuscale: Allow rcuscale without RCU Tasks Rude/Trace
  rcuscale: Allow rcuscale without RCU Tasks
  refscale: Allow refscale without RCU Tasks Rude/Trace
  refscale: Allow refscale without RCU Tasks
  rcutorture: Allow specifying per-scenario stat_interval
  ...
2022-05-23 11:46:51 -07:00
Peter Zijlstra
546a3fee17 sched: Reverse sched_class layout
Because GCC-12 is fully stupid about array bounds and it's just really
hard to get a solid array definition from a linker script, flip the
array order to avoid needing negative offsets :-/

This makes the whole relational pointer magic a little less obvious, but
alas.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/YoOLLmLG7HRTXeEm@hirez.programming.kicks-ass.net
2022-05-19 23:46:13 +02:00
Delyan Kratunov
9c2136be08 sched/tracing: Append prev_state to tp args instead
Commit fa2c3254d7 (sched/tracing: Don't re-read p->state when emitting
sched_switch event, 2022-01-20) added a new prev_state argument to the
sched_switch tracepoint, before the prev task_struct pointer.

This reordering of arguments broke BPF programs that use the raw
tracepoint (e.g. tp_btf programs). The type of the second argument has
changed and existing programs that assume a task_struct* argument
(e.g. for bpf_task_storage access) will now fail to verify.

If we instead append the new argument to the end, all existing programs
would continue to work and can conditionally extract the prev_state
argument on supported kernel versions.

Fixes: fa2c3254d7 (sched/tracing: Don't re-read p->state when emitting sched_switch event, 2022-01-20)
Signed-off-by: Delyan Kratunov <delyank@fb.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lkml.kernel.org/r/c8a6930dfdd58a4a5755fc01732675472979732b.camel@fb.com
2022-05-12 00:37:11 +02:00
Eric W. Biederman
2500ad1c7f ptrace: Don't change __state
Stop playing with tsk->__state to remove TASK_WAKEKILL while a ptrace
command is executing.

Instead remove TASK_WAKEKILL from the definition of TASK_TRACED, and
implement a new jobctl flag TASK_PTRACE_FROZEN.  This new flag is set
in jobctl_freeze_task and cleared when ptrace_stop is awoken or in
jobctl_unfreeze_task (when ptrace_stop remains asleep).

In signal_wake_up add __TASK_TRACED to state along with TASK_WAKEKILL
when the wake up is for a fatal signal.  Skip adding __TASK_TRACED
when TASK_PTRACE_FROZEN is not set.  This has the same effect as
changing TASK_TRACED to __TASK_TRACED as all of the wake_ups that use
TASK_KILLABLE go through signal_wake_up.

Handle a ptrace_stop being called with a pending fatal signal.
Previously it would have been handled by schedule simply failing to
sleep.  As TASK_WAKEKILL is no longer part of TASK_TRACED schedule
will sleep with a fatal_signal_pending.   The code in signal_wake_up
guarantees that the code will be awaked by any fatal signal that
codes after TASK_TRACED is set.

Previously the __state value of __TASK_TRACED was changed to
TASK_RUNNING when woken up or back to TASK_TRACED when the code was
left in ptrace_stop.  Now when woken up ptrace_stop now clears
JOBCTL_PTRACE_FROZEN and when left sleeping ptrace_unfreezed_traced
clears JOBCTL_PTRACE_FROZEN.

Tested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lkml.kernel.org/r/20220505182645.497868-10-ebiederm@xmission.com
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2022-05-11 14:35:32 -05:00
Hao Jia
2679a83731 sched/core: Avoid obvious double update_rq_clock warning
When we use raw_spin_rq_lock() to acquire the rq lock and have to
update the rq clock while holding the lock, the kernel may issue
a WARN_DOUBLE_CLOCK warning.

Since we directly use raw_spin_rq_lock() to acquire rq lock instead of
rq_lock(), there is no corresponding change to rq->clock_update_flags.
In particular, we have obtained the rq lock of other CPUs, the
rq->clock_update_flags of this CPU may be RQCF_UPDATED at this time, and
then calling update_rq_clock() will trigger the WARN_DOUBLE_CLOCK warning.

So we need to clear RQCF_UPDATED of rq->clock_update_flags to avoid
the WARN_DOUBLE_CLOCK warning.

For the sched_rt_period_timer() and migrate_task_rq_dl() cases
we simply replace raw_spin_rq_lock()/raw_spin_rq_unlock() with
rq_lock()/rq_unlock().

For the {pull,push}_{rt,dl}_task() cases, we add the
double_rq_clock_clear_update() function to clear RQCF_UPDATED of
rq->clock_update_flags, and call double_rq_clock_clear_update()
before double_lock_balance()/double_rq_lock() returns to avoid the
WARN_DOUBLE_CLOCK warning.

Some call trace reports:
Call Trace 1:
 <IRQ>
 sched_rt_period_timer+0x10f/0x3a0
 ? enqueue_top_rt_rq+0x110/0x110
 __hrtimer_run_queues+0x1a9/0x490
 hrtimer_interrupt+0x10b/0x240
 __sysvec_apic_timer_interrupt+0x8a/0x250
 sysvec_apic_timer_interrupt+0x9a/0xd0
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x12/0x20

Call Trace 2:
 <TASK>
 activate_task+0x8b/0x110
 push_rt_task.part.108+0x241/0x2c0
 push_rt_tasks+0x15/0x30
 finish_task_switch+0xaa/0x2e0
 ? __switch_to+0x134/0x420
 __schedule+0x343/0x8e0
 ? hrtimer_start_range_ns+0x101/0x340
 schedule+0x4e/0xb0
 do_nanosleep+0x8e/0x160
 hrtimer_nanosleep+0x89/0x120
 ? hrtimer_init_sleeper+0x90/0x90
 __x64_sys_nanosleep+0x96/0xd0
 do_syscall_64+0x34/0x90
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Call Trace 3:
 <TASK>
 deactivate_task+0x93/0xe0
 pull_rt_task+0x33e/0x400
 balance_rt+0x7e/0x90
 __schedule+0x62f/0x8e0
 do_task_dead+0x3f/0x50
 do_exit+0x7b8/0xbb0
 do_group_exit+0x2d/0x90
 get_signal+0x9df/0x9e0
 ? preempt_count_add+0x56/0xa0
 ? __remove_hrtimer+0x35/0x70
 arch_do_signal_or_restart+0x36/0x720
 ? nanosleep_copyout+0x39/0x50
 ? do_nanosleep+0x131/0x160
 ? audit_filter_inodes+0xf5/0x120
 exit_to_user_mode_prepare+0x10f/0x1e0
 syscall_exit_to_user_mode+0x17/0x30
 do_syscall_64+0x40/0x90
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Call Trace 4:
 update_rq_clock+0x128/0x1a0
 migrate_task_rq_dl+0xec/0x310
 set_task_cpu+0x84/0x1e4
 try_to_wake_up+0x1d8/0x5c0
 wake_up_process+0x1c/0x30
 hrtimer_wakeup+0x24/0x3c
 __hrtimer_run_queues+0x114/0x270
 hrtimer_interrupt+0xe8/0x244
 arch_timer_handler_phys+0x30/0x50
 handle_percpu_devid_irq+0x88/0x140
 generic_handle_domain_irq+0x40/0x60
 gic_handle_irq+0x48/0xe0
 call_on_irq_stack+0x2c/0x60
 do_interrupt_handler+0x80/0x84

Steps to reproduce:
1. Enable CONFIG_SCHED_DEBUG when compiling the kernel
2. echo 1 > /sys/kernel/debug/clear_warn_once
   echo "WARN_DOUBLE_CLOCK" > /sys/kernel/debug/sched/features
   echo "NO_RT_PUSH_IPI" > /sys/kernel/debug/sched/features
3. Run some rt/dl tasks that periodically work and sleep, e.g.
Create 2*n rt or dl (90% running) tasks via rt-app (on a system
with n CPUs), and Dietmar Eggemann reports Call Trace 4 when running
on PREEMPT_RT kernel.

Signed-off-by: Hao Jia <jiahao.os@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lore.kernel.org/r/20220430085843.62939-2-jiahao.os@bytedance.com
2022-05-11 16:27:11 +02:00
YueHaibing
494dcdf46e sched: Fix build warning without CONFIG_SYSCTL
IF CONFIG_SYSCTL is n, build warn:

kernel/sched/core.c:1782:12: warning: ‘sysctl_sched_uclamp_handler’ defined but not used [-Wunused-function]
 static int sysctl_sched_uclamp_handler(struct ctl_table *table, int write,
            ^~~~~~~~~~~~~~~~~~~~~~~~~~~

sysctl_sched_uclamp_handler() is used while CONFIG_SYSCTL enabled,
wrap all related code with CONFIG_SYSCTL to fix this.

Fixes: 3267e0156c ("sched: Move uclamp_util sysctls to core.c")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
2022-05-09 16:54:57 -07:00
Ingo Molnar
d70522fc54 Linux 5.18-rc5
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Merge tag 'v5.18-rc5' into sched/core to pull in fixes & to resolve a conflict

 - sched/core is on a pretty old -rc1 base - refresh it to include recent fixes.
 - this also allows up to resolve a (trivial) .mailmap conflict

Conflicts:
	.mailmap

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2022-05-06 10:21:46 +02:00
Thomas Gleixner
16bf5a5e1e smp: Rename flush_smp_call_function_from_idle()
This is invoked from the stopper thread too, which is definitely not idle.
Rename it to flush_smp_call_function_queue() and fixup the callers.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220413133024.305001096@linutronix.de
2022-05-01 10:03:43 +02:00
Thomas Gleixner
d664e39912 sched: Fix missing prototype warnings
A W=1 build emits more than a dozen missing prototype warnings related to
scheduler and scheduler specific includes.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220413133024.249118058@linutronix.de
2022-05-01 10:03:43 +02:00
Zhen Ni
3267e0156c sched: Move uclamp_util sysctls to core.c
move uclamp_util sysctls to core.c and use the new
register_sysctl_init() to register the sysctl interface.

Signed-off-by: Zhen Ni <nizhen@uniontech.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
2022-04-06 13:43:43 -07:00
Zhen Ni
d9ab0e63fa sched: Move rt_period/runtime sysctls to rt.c
move rt_period/runtime sysctls to rt.c and use the new
register_sysctl_init() to register the sysctl interface.

Signed-off-by: Zhen Ni <nizhen@uniontech.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
2022-04-06 13:43:43 -07:00
Zhen Ni
f5ef06d58b sched: Move schedstats sysctls to core.c
move schedstats sysctls to core.c and use the new
register_sysctl_init() to register the sysctl interface.

Signed-off-by: Zhen Ni <nizhen@uniontech.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
2022-04-06 13:43:43 -07:00
Valentin Schneider
cfe43f478b preempt/dynamic: Introduce preemption model accessors
CONFIG_PREEMPT{_NONE, _VOLUNTARY} designate either:
o The build-time preemption model when !PREEMPT_DYNAMIC
o The default boot-time preemption model when PREEMPT_DYNAMIC

IOW, using those on PREEMPT_DYNAMIC kernels is meaningless - the actual
model could have been set to something else by the "preempt=foo" cmdline
parameter. Same problem applies to CONFIG_PREEMPTION.

Introduce a set of helpers to determine the actual preemption model used by
the live kernel.

Suggested-by: Marco Elver <elver@google.com>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Marco Elver <elver@google.com>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20211112185203.280040-3-valentin.schneider@arm.com
2022-04-05 10:24:42 +02:00
Sebastian Andrzej Siewior
386ef214c3 sched: Teach the forced-newidle balancer about CPU affinity limitation.
try_steal_cookie() looks at task_struct::cpus_mask to decide if the
task could be moved to `this' CPU. It ignores that the task might be in
a migration disabled section while not on the CPU. In this case the task
must not be moved otherwise per-CPU assumption are broken.

Use is_cpu_allowed(), as suggested by Peter Zijlstra, to decide if the a
task can be moved.

Fixes: d2dfa17bc7 ("sched: Trivial forced-newidle balancer")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/YjNK9El+3fzGmswf@linutronix.de
2022-04-05 09:59:36 +02:00
Peter Zijlstra
5b6547ed97 sched/core: Fix forceidle balancing
Steve reported that ChromeOS encounters the forceidle balancer being
ran from rt_mutex_setprio()'s balance_callback() invocation and
explodes.

Now, the forceidle balancer gets queued every time the idle task gets
selected, set_next_task(), which is strictly too often.
rt_mutex_setprio() also uses set_next_task() in the 'change' pattern:

	queued = task_on_rq_queued(p); /* p->on_rq == TASK_ON_RQ_QUEUED */
	running = task_current(rq, p); /* rq->curr == p */

	if (queued)
		dequeue_task(...);
	if (running)
		put_prev_task(...);

	/* change task properties */

	if (queued)
		enqueue_task(...);
	if (running)
		set_next_task(...);

However, rt_mutex_setprio() will explicitly not run this pattern on
the idle task (since priority boosting the idle task is quite insane).
Most other 'change' pattern users are pidhash based and would also not
apply to idle.

Also, the change pattern doesn't contain a __balance_callback()
invocation and hence we could have an out-of-band balance-callback,
which *should* trigger the WARN in rq_pin_lock() (which guards against
this exact anti-pattern).

So while none of that explains how this happens, it does indicate that
having it in set_next_task() might not be the most robust option.

Instead, explicitly queue the forceidle balancer from pick_next_task()
when it does indeed result in forceidle selection. Having it here,
ensures it can only be triggered under the __schedule() rq->lock
instance, and hence must be ran from that context.

This also happens to clean up the code a little, so win-win.

Fixes: d2dfa17bc7 ("sched: Trivial forced-newidle balancer")
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: T.J. Alumbaugh <talumbau@chromium.org>
Link: https://lkml.kernel.org/r/20220330160535.GN8939@worktop.programming.kicks-ass.net
2022-04-05 09:59:36 +02:00
Linus Torvalds
3bf03b9a08 Merge branch 'akpm' (patches from Andrew)
Merge updates from Andrew Morton:

 - A few misc subsystems: kthread, scripts, ntfs, ocfs2, block, and vfs

 - Most the MM patches which precede the patches in Willy's tree: kasan,
   pagecache, gup, swap, shmem, memcg, selftests, pagemap, mremap,
   sparsemem, vmalloc, pagealloc, memory-failure, mlock, hugetlb,
   userfaultfd, vmscan, compaction, mempolicy, oom-kill, migration, thp,
   cma, autonuma, psi, ksm, page-poison, madvise, memory-hotplug, rmap,
   zswap, uaccess, ioremap, highmem, cleanups, kfence, hmm, and damon.

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (227 commits)
  mm/damon/sysfs: remove repeat container_of() in damon_sysfs_kdamond_release()
  Docs/ABI/testing: add DAMON sysfs interface ABI document
  Docs/admin-guide/mm/damon/usage: document DAMON sysfs interface
  selftests/damon: add a test for DAMON sysfs interface
  mm/damon/sysfs: support DAMOS stats
  mm/damon/sysfs: support DAMOS watermarks
  mm/damon/sysfs: support schemes prioritization
  mm/damon/sysfs: support DAMOS quotas
  mm/damon/sysfs: support DAMON-based Operation Schemes
  mm/damon/sysfs: support the physical address space monitoring
  mm/damon/sysfs: link DAMON for virtual address spaces monitoring
  mm/damon: implement a minimal stub for sysfs-based DAMON interface
  mm/damon/core: add number of each enum type values
  mm/damon/core: allow non-exclusive DAMON start/stop
  Docs/damon: update outdated term 'regions update interval'
  Docs/vm/damon/design: update DAMON-Idle Page Tracking interference handling
  Docs/vm/damon: call low level monitoring primitives the operations
  mm/damon: remove unnecessary CONFIG_DAMON option
  mm/damon/paddr,vaddr: remove damon_{p,v}a_{target_valid,set_operations}()
  mm/damon/dbgfs-test: fix is_target_id() change
  ...
2022-03-22 16:11:53 -07:00
Huang Ying
c574bbe917 NUMA balancing: optimize page placement for memory tiering system
With the advent of various new memory types, some machines will have
multiple types of memory, e.g.  DRAM and PMEM (persistent memory).  The
memory subsystem of these machines can be called memory tiering system,
because the performance of the different types of memory are usually
different.

In such system, because of the memory accessing pattern changing etc,
some pages in the slow memory may become hot globally.  So in this
patch, the NUMA balancing mechanism is enhanced to optimize the page
placement among the different memory types according to hot/cold
dynamically.

In a typical memory tiering system, there are CPUs, fast memory and slow
memory in each physical NUMA node.  The CPUs and the fast memory will be
put in one logical node (called fast memory node), while the slow memory
will be put in another (faked) logical node (called slow memory node).
That is, the fast memory is regarded as local while the slow memory is
regarded as remote.  So it's possible for the recently accessed pages in
the slow memory node to be promoted to the fast memory node via the
existing NUMA balancing mechanism.

The original NUMA balancing mechanism will stop to migrate pages if the
free memory of the target node becomes below the high watermark.  This
is a reasonable policy if there's only one memory type.  But this makes
the original NUMA balancing mechanism almost do not work to optimize
page placement among different memory types.  Details are as follows.

It's the common cases that the working-set size of the workload is
larger than the size of the fast memory nodes.  Otherwise, it's
unnecessary to use the slow memory at all.  So, there are almost always
no enough free pages in the fast memory nodes, so that the globally hot
pages in the slow memory node cannot be promoted to the fast memory
node.  To solve the issue, we have 2 choices as follows,

a. Ignore the free pages watermark checking when promoting hot pages
   from the slow memory node to the fast memory node.  This will
   create some memory pressure in the fast memory node, thus trigger
   the memory reclaiming.  So that, the cold pages in the fast memory
   node will be demoted to the slow memory node.

b. Define a new watermark called wmark_promo which is higher than
   wmark_high, and have kswapd reclaiming pages until free pages reach
   such watermark.  The scenario is as follows: when we want to promote
   hot-pages from a slow memory to a fast memory, but fast memory's free
   pages would go lower than high watermark with such promotion, we wake
   up kswapd with wmark_promo watermark in order to demote cold pages and
   free us up some space.  So, next time we want to promote hot-pages we
   might have a chance of doing so.

The choice "a" may create high memory pressure in the fast memory node.
If the memory pressure of the workload is high, the memory pressure
may become so high that the memory allocation latency of the workload
is influenced, e.g.  the direct reclaiming may be triggered.

The choice "b" works much better at this aspect.  If the memory
pressure of the workload is high, the hot pages promotion will stop
earlier because its allocation watermark is higher than that of the
normal memory allocation.  So in this patch, choice "b" is implemented.
A new zone watermark (WMARK_PROMO) is added.  Which is larger than the
high watermark and can be controlled via watermark_scale_factor.

In addition to the original page placement optimization among sockets,
the NUMA balancing mechanism is extended to be used to optimize page
placement according to hot/cold among different memory types.  So the
sysctl user space interface (numa_balancing) is extended in a backward
compatible way as follow, so that the users can enable/disable these
functionality individually.

The sysctl is converted from a Boolean value to a bits field.  The
definition of the flags is,

- 0: NUMA_BALANCING_DISABLED
- 1: NUMA_BALANCING_NORMAL
- 2: NUMA_BALANCING_MEMORY_TIERING

We have tested the patch with the pmbench memory accessing benchmark
with the 80:20 read/write ratio and the Gauss access address
distribution on a 2 socket Intel server with Optane DC Persistent
Memory Model.  The test results shows that the pmbench score can
improve up to 95.9%.

Thanks Andrew Morton to help fix the document format error.

Link: https://lkml.kernel.org/r/20220221084529.1052339-3-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Wei Xu <weixugc@google.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: zhongjiang-ali <zhongjiang-ali@linux.alibaba.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Feng Tang <feng.tang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-03-22 15:57:09 -07:00
Linus Torvalds
3fe2f7446f Changes in this cycle were:
- Cleanups for SCHED_DEADLINE
  - Tracing updates/fixes
  - CPU Accounting fixes
  - First wave of changes to optimize the overhead of the scheduler build,
    from the fast-headers tree - including placeholder *_api.h headers for
    later header split-ups.
  - Preempt-dynamic using static_branch() for ARM64
  - Isolation housekeeping mask rework; preperatory for further changes
  - NUMA-balancing: deal with CPU-less nodes
  - NUMA-balancing: tune systems that have multiple LLC cache domains per node (eg. AMD)
  - Updates to RSEQ UAPI in preparation for glibc usage
  - Lots of RSEQ/selftests, for same
  - Add Suren as PSI co-maintainer
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-core-2022-03-22' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler updates from Ingo Molnar:

 - Cleanups for SCHED_DEADLINE

 - Tracing updates/fixes

 - CPU Accounting fixes

 - First wave of changes to optimize the overhead of the scheduler
   build, from the fast-headers tree - including placeholder *_api.h
   headers for later header split-ups.

 - Preempt-dynamic using static_branch() for ARM64

 - Isolation housekeeping mask rework; preperatory for further changes

 - NUMA-balancing: deal with CPU-less nodes

 - NUMA-balancing: tune systems that have multiple LLC cache domains per
   node (eg. AMD)

 - Updates to RSEQ UAPI in preparation for glibc usage

 - Lots of RSEQ/selftests, for same

 - Add Suren as PSI co-maintainer

* tag 'sched-core-2022-03-22' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (81 commits)
  sched/headers: ARM needs asm/paravirt_api_clock.h too
  sched/numa: Fix boot crash on arm64 systems
  headers/prep: Fix header to build standalone: <linux/psi.h>
  sched/headers: Only include <linux/entry-common.h> when CONFIG_GENERIC_ENTRY=y
  cgroup: Fix suspicious rcu_dereference_check() usage warning
  sched/preempt: Tell about PREEMPT_DYNAMIC on kernel headers
  sched/topology: Remove redundant variable and fix incorrect type in build_sched_domains
  sched/deadline,rt: Remove unused parameter from pick_next_[rt|dl]_entity()
  sched/deadline,rt: Remove unused functions for !CONFIG_SMP
  sched/deadline: Use __node_2_[pdl|dle]() and rb_first_cached() consistently
  sched/deadline: Merge dl_task_can_attach() and dl_cpu_busy()
  sched/deadline: Move bandwidth mgmt and reclaim functions into sched class source file
  sched/deadline: Remove unused def_dl_bandwidth
  sched/tracing: Report TASK_RTLOCK_WAIT tasks as TASK_UNINTERRUPTIBLE
  sched/tracing: Don't re-read p->state when emitting sched_switch event
  sched/rt: Plug rt_mutex_setprio() vs push_rt_task() race
  sched/cpuacct: Remove redundant RCU read lock
  sched/cpuacct: Optimize away RCU read lock
  sched/cpuacct: Fix charge percpu cpuusage
  sched/headers: Reorganize, clean up and optimize kernel/sched/sched.h dependencies
  ...
2022-03-22 14:39:12 -07:00
Linus Torvalds
616355cc81 for-5.18/block-2022-03-18
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Merge tag 'for-5.18/block-2022-03-18' of git://git.kernel.dk/linux-block

Pull block updates from Jens Axboe:

 - BFQ cleanups and fixes (Yu, Zhang, Yahu, Paolo)

 - blk-rq-qos completion fix (Tejun)

 - blk-cgroup merge fix (Tejun)

 - Add offline error return value to distinguish it from an IO error on
   the device (Song)

 - IO stats fixes (Zhang, Christoph)

 - blkcg refcount fixes (Ming, Yu)

 - Fix for indefinite dispatch loop softlockup (Shin'ichiro)

 - blk-mq hardware queue management improvements (Ming)

 - sbitmap dead code removal (Ming, John)

 - Plugging merge improvements (me)

 - Show blk-crypto capabilities in sysfs (Eric)

 - Multiple delayed queue run improvement (David)

 - Block throttling fixes (Ming)

 - Start deprecating auto module loading based on dev_t (Christoph)

 - bio allocation improvements (Christoph, Chaitanya)

 - Get rid of bio_devname (Christoph)

 - bio clone improvements (Christoph)

 - Block plugging improvements (Christoph)

 - Get rid of genhd.h header (Christoph)

 - Ensure drivers use appropriate flush helpers (Christoph)

 - Refcounting improvements (Christoph)

 - Queue initialization and teardown improvements (Ming, Christoph)

 - Misc fixes/improvements (Barry, Chaitanya, Colin, Dan, Jiapeng,
   Lukas, Nian, Yang, Eric, Chengming)

* tag 'for-5.18/block-2022-03-18' of git://git.kernel.dk/linux-block: (127 commits)
  block: cancel all throttled bios in del_gendisk()
  block: let blkcg_gq grab request queue's refcnt
  block: avoid use-after-free on throttle data
  block: limit request dispatch loop duration
  block/bfq-iosched: Fix spelling mistake "tenative" -> "tentative"
  sr: simplify the local variable initialization in sr_block_open()
  block: don't merge across cgroup boundaries if blkcg is enabled
  block: fix rq-qos breakage from skipping rq_qos_done_bio()
  block: flush plug based on hardware and software queue order
  block: ensure plug merging checks the correct queue at least once
  block: move rq_qos_exit() into disk_release()
  block: do more work in elevator_exit
  block: move blk_exit_queue into disk_release
  block: move q_usage_counter release into blk_queue_release
  block: don't remove hctx debugfs dir from blk_mq_exit_queue
  block: move blkcg initialization/destroy into disk allocation/release handler
  sr: implement ->free_disk to simplify refcounting
  sd: implement ->free_disk to simplify refcounting
  sd: delay calling free_opal_dev
  sd: call sd_zbc_release_disk before releasing the scsi_device reference
  ...
2022-03-21 16:48:55 -07:00
Ingo Molnar
a7b2553b5e sched/headers: Only include <linux/entry-common.h> when CONFIG_GENERIC_ENTRY=y
This header is not (yet) standalone.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2022-03-15 10:33:53 +01:00
Ingo Molnar
ccacfe56d7 Merge branch 'sched/fast-headers' into sched/core
Merge the scheduler build speedup of the fast-headers tree.

Cumulative scheduler (kernel/sched/) build time speedup on a
Linux distribution's config, which enables all scheduler features,
compared to the vanilla kernel:

      _____________________________________________________________________________
     |
     |  Vanilla kernel (v5.13-rc7):
     |_____________________________________________________________________________
     |
     |  Performance counter stats for 'make -j96 kernel/sched/' (3 runs):
     |
     |   126,975,564,374      instructions              #    1.45  insn per cycle           ( +-  0.00% )
     |    87,637,847,671      cycles                    #    3.959 GHz                      ( +-  0.30% )
     |         22,136.96 msec cpu-clock                 #    7.499 CPUs utilized            ( +-  0.29% )
     |
     |            2.9520 +- 0.0169 seconds time elapsed  ( +-  0.57% )
     |_____________________________________________________________________________
     |
     |  Patched kernel:
     |_____________________________________________________________________________
     |
     | Performance counter stats for 'make -j96 kernel/sched/' (3 runs):
     |
     |    50,420,496,914      instructions              #    1.47  insn per cycle           ( +-  0.00% )
     |    34,234,322,038      cycles                    #    3.946 GHz                      ( +-  0.31% )
     |          8,675.81 msec cpu-clock                 #    3.053 CPUs utilized            ( +-  0.45% )
     |
     |            2.8420 +- 0.0181 seconds time elapsed  ( +-  0.64% )
     |_____________________________________________________________________________

    Summary:

      - CPU time used to build the scheduler dropped by -60.9%, a reduction
        from 22.1 clock-seconds to 8.7 clock-seconds.

      - Wall-clock time to build the scheduler dropped by -3.9%, a reduction
        from 2.95 seconds to 2.84 seconds.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2022-03-15 09:05:05 +01:00
Dietmar Eggemann
772b6539fd sched/deadline: Merge dl_task_can_attach() and dl_cpu_busy()
Both functions are doing almost the same, that is checking if admission
control is still respected.

With exclusive cpusets, dl_task_can_attach() checks if the destination
cpuset (i.e. its root domain) has enough CPU capacity to accommodate the
task.
dl_cpu_busy() checks if there is enough CPU capacity in the cpuset in
case the CPU is hot-plugged out.

dl_task_can_attach() is used to check if a task can be admitted while
dl_cpu_busy() is used to check if a CPU can be hotplugged out.

Make dl_cpu_busy() able to deal with a task and use it instead of
dl_task_can_attach() in task_can_attach().

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lore.kernel.org/r/20220302183433.333029-4-dietmar.eggemann@arm.com
2022-03-08 16:08:39 +01:00
Dietmar Eggemann
eb77cf1c15 sched/deadline: Remove unused def_dl_bandwidth
Since commit 1724813d9f ("sched/deadline: Remove the sysctl_sched_dl
knobs") the default deadline bandwidth control structure has no purpose.
Remove it.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lore.kernel.org/r/20220302183433.333029-2-dietmar.eggemann@arm.com
2022-03-08 16:08:38 +01:00
Valentin Schneider
fa2c3254d7 sched/tracing: Don't re-read p->state when emitting sched_switch event
As of commit

  c6e7bd7afa ("sched/core: Optimize ttwu() spinning on p->on_cpu")

the following sequence becomes possible:

		      p->__state = TASK_INTERRUPTIBLE;
		      __schedule()
			deactivate_task(p);
  ttwu()
    READ !p->on_rq
    p->__state=TASK_WAKING
			trace_sched_switch()
			  __trace_sched_switch_state()
			    task_state_index()
			      return 0;

TASK_WAKING isn't in TASK_REPORT, so the task appears as TASK_RUNNING in
the trace event.

Prevent this by pushing the value read from __schedule() down the trace
event.

Reported-by: Abhijeet Dharmapurikar <adharmap@quicinc.com>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/20220120162520.570782-2-valentin.schneider@arm.com
2022-03-01 16:18:39 +01:00
Ingo Molnar
e66f6481a8 sched/headers: Reorganize, clean up and optimize kernel/sched/core.c dependencies
Use all generic headers from kernel/sched/sched.h that are required
for it to build.

Sort the sections alphabetically.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Peter Zijlstra <peterz@infradead.org>
2022-02-23 10:58:33 +01:00
Ingo Molnar
b9e9c6ca6e sched/headers: Standardize kernel/sched/sched.h header dependencies
kernel/sched/sched.h is a weird mix of ad-hoc headers included
in the middle of the header.

Two of them rely on being included in the middle of kernel/sched/sched.h,
due to definitions they require:

 - "stat.h" needs the rq definitions.
 - "autogroup.h" needs the task_group definition.

Move the inclusion of these two files out of kernel/sched/sched.h, and
include them in all files that require them.

Move of the rest of the header dependencies to the top of the
kernel/sched/sched.h file.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Peter Zijlstra <peterz@infradead.org>
2022-02-23 10:58:33 +01:00
Ingo Molnar
6255b48aeb Linux 5.17-rc5
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Merge tag 'v5.17-rc5' into sched/core, to resolve conflicts

New conflicts in sched/core due to the following upstream fixes:

  44585f7bc0 ("psi: fix "defined but not used" warnings when CONFIG_PROC_FS=n")
  a06247c680 ("psi: Fix uaf issue when psi trigger is destroyed while being polled")

Conflicts:
	include/linux/psi_types.h
	kernel/sched/psi.c

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2022-02-21 11:53:51 +01:00
Mark Rutland
99cf983cc8 sched/preempt: Add PREEMPT_DYNAMIC using static keys
Where an architecture selects HAVE_STATIC_CALL but not
HAVE_STATIC_CALL_INLINE, each static call has an out-of-line trampoline
which will either branch to a callee or return to the caller.

On such architectures, a number of constraints can conspire to make
those trampolines more complicated and potentially less useful than we'd
like. For example:

* Hardware and software control flow integrity schemes can require the
  addition of "landing pad" instructions (e.g. `BTI` for arm64), which
  will also be present at the "real" callee.

* Limited branch ranges can require that trampolines generate or load an
  address into a register and perform an indirect branch (or at least
  have a slow path that does so). This loses some of the benefits of
  having a direct branch.

* Interaction with SW CFI schemes can be complicated and fragile, e.g.
  requiring that we can recognise idiomatic codegen and remove
  indirections understand, at least until clang proves more helpful
  mechanisms for dealing with this.

For PREEMPT_DYNAMIC, we don't need the full power of static calls, as we
really only need to enable/disable specific preemption functions. We can
achieve the same effect without a number of the pain points above by
using static keys to fold early returns into the preemption functions
themselves rather than in an out-of-line trampoline, effectively
inlining the trampoline into the start of the function.

For arm64, this results in good code generation. For example, the
dynamic_cond_resched() wrapper looks as follows when enabled. When
disabled, the first `B` is replaced with a `NOP`, resulting in an early
return.

| <dynamic_cond_resched>:
|        bti     c
|        b       <dynamic_cond_resched+0x10>     // or `nop`
|        mov     w0, #0x0
|        ret
|        mrs     x0, sp_el0
|        ldr     x0, [x0, #8]
|        cbnz    x0, <dynamic_cond_resched+0x8>
|        paciasp
|        stp     x29, x30, [sp, #-16]!
|        mov     x29, sp
|        bl      <preempt_schedule_common>
|        mov     w0, #0x1
|        ldp     x29, x30, [sp], #16
|        autiasp
|        ret

... compared to the regular form of the function:

| <__cond_resched>:
|        bti     c
|        mrs     x0, sp_el0
|        ldr     x1, [x0, #8]
|        cbz     x1, <__cond_resched+0x18>
|        mov     w0, #0x0
|        ret
|        paciasp
|        stp     x29, x30, [sp, #-16]!
|        mov     x29, sp
|        bl      <preempt_schedule_common>
|        mov     w0, #0x1
|        ldp     x29, x30, [sp], #16
|        autiasp
|        ret

Any architecture which implements static keys should be able to use this
to implement PREEMPT_DYNAMIC with similar cost to non-inlined static
calls. Since this is likely to have greater overhead than (inlined)
static calls, PREEMPT_DYNAMIC is only defaulted to enabled when
HAVE_PREEMPT_DYNAMIC_CALL is selected.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20220214165216.2231574-6-mark.rutland@arm.com
2022-02-19 11:11:08 +01:00
Mark Rutland
33c64734be sched/preempt: Decouple HAVE_PREEMPT_DYNAMIC from GENERIC_ENTRY
Now that the enabled/disabled states for the preemption functions are
declared alongside their definitions, the core PREEMPT_DYNAMIC logic is
no longer tied to GENERIC_ENTRY, and can safely be selected so long as
an architecture provides enabled/disabled states for
irqentry_exit_cond_resched().

Make it possible to select HAVE_PREEMPT_DYNAMIC without GENERIC_ENTRY.

For existing users of HAVE_PREEMPT_DYNAMIC there should be no functional
change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20220214165216.2231574-5-mark.rutland@arm.com
2022-02-19 11:11:08 +01:00