linux-stable.git/kernel/sched/fair.c, branch v6.1.78 Linux kernel stable tree sched: Fix stop_one_cpu_nowait() vs hotplug 2023-11-20T10:51:50+00:00 Peter Zijlstra peterz@infradead.org 2023-10-10T18:57:39+00:00 8620933c3c53e128b9d4982de9a8808142654106 [ Upstream commit f0498d2a54e7966ce23cd7c7ff42c64fa0059b07 ] Kuyo reported sporadic failures on a sched_setaffinity() vs CPU hotplug stress-test -- notably affine_move_task() remains stuck in wait_for_completion(), leading to a hung-task detector warning. Specifically, it was reported that stop_one_cpu_nowait(.fn = migration_cpu_stop) returns false -- this stopper is responsible for the matching complete(). The race scenario is: CPU0 CPU1 // doing _cpu_down() __set_cpus_allowed_ptr() task_rq_lock(); takedown_cpu() stop_machine_cpuslocked(take_cpu_down..) <PREEMPT: cpu_stopper_thread() MULTI_STOP_PREPARE ... __set_cpus_allowed_ptr_locked() affine_move_task() task_rq_unlock(); <PREEMPT: cpu_stopper_thread()\> ack_state() MULTI_STOP_RUN take_cpu_down() __cpu_disable(); stop_machine_park(); stopper->enabled = false; /> /> stop_one_cpu_nowait(.fn = migration_cpu_stop); if (stopper->enabled) // false!!! That is, by doing stop_one_cpu_nowait() after dropping rq-lock, the stopper thread gets a chance to preempt and allows the cpu-down for the target CPU to complete. OTOH, since stop_one_cpu_nowait() / cpu_stop_queue_work() needs to issue a wakeup, it must not be ran under the scheduler locks. Solve this apparent contradiction by keeping preemption disabled over the unlock + queue_stopper combination: preempt_disable(); task_rq_unlock(...); if (!stop_pending) stop_one_cpu_nowait(...) preempt_enable(); This respects the lock ordering contraints while still avoiding the above race. That is, if we find the CPU is online under rq-lock, the targeted stop_one_cpu_nowait() must succeed. Apply this pattern to all similar stop_one_cpu_nowait() invocations. Fixes: 6d337eab041d ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()") Reported-by: "Kuyo Chang (張建文)" <Kuyo.Chang@mediatek.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: "Kuyo Chang (張建文)" <Kuyo.Chang@mediatek.com> Link: https://lkml.kernel.org/r/20231010200442.GA16515@noisy.programming.kicks-ass.net Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit f0498d2a54e7966ce23cd7c7ff42c64fa0059b07 ]

Kuyo reported sporadic failures on a sched_setaffinity() vs CPU
hotplug stress-test -- notably affine_move_task() remains stuck in
wait_for_completion(), leading to a hung-task detector warning.

Specifically, it was reported that stop_one_cpu_nowait(.fn =
migration_cpu_stop) returns false -- this stopper is responsible for
the matching complete().

The race scenario is:

	CPU0					CPU1

					// doing _cpu_down()

  __set_cpus_allowed_ptr()
    task_rq_lock();
					takedown_cpu()
					  stop_machine_cpuslocked(take_cpu_down..)

					<PREEMPT: cpu_stopper_thread()
					  MULTI_STOP_PREPARE
					  ...
    __set_cpus_allowed_ptr_locked()
      affine_move_task()
        task_rq_unlock();

  <PREEMPT: cpu_stopper_thread()\>
    ack_state()
					  MULTI_STOP_RUN
					    take_cpu_down()
					      __cpu_disable();
					      stop_machine_park();
						stopper->enabled = false;
					 />
   />
	stop_one_cpu_nowait(.fn = migration_cpu_stop);
          if (stopper->enabled) // false!!!

That is, by doing stop_one_cpu_nowait() after dropping rq-lock, the
stopper thread gets a chance to preempt and allows the cpu-down for
the target CPU to complete.

OTOH, since stop_one_cpu_nowait() / cpu_stop_queue_work() needs to
issue a wakeup, it must not be ran under the scheduler locks.

Solve this apparent contradiction by keeping preemption disabled over
the unlock + queue_stopper combination:

	preempt_disable();
	task_rq_unlock(...);
	if (!stop_pending)
	  stop_one_cpu_nowait(...)
	preempt_enable();

This respects the lock ordering contraints while still avoiding the
above race. That is, if we find the CPU is online under rq-lock, the
targeted stop_one_cpu_nowait() must succeed.

Apply this pattern to all similar stop_one_cpu_nowait() invocations.

Fixes: 6d337eab041d ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Reported-by: "Kuyo Chang (張建文)" <Kuyo.Chang@mediatek.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: "Kuyo Chang (張建文)" <Kuyo.Chang@mediatek.com>
Link: https://lkml.kernel.org/r/20231010200442.GA16515@noisy.programming.kicks-ass.net
Signed-off-by: Sasha Levin <sashal@kernel.org>
sched/uclamp: Ignore (util == 0) optimization in feec() when p_util_max = 0 2023-11-20T10:51:50+00:00 Qais Yousef qyousef@layalina.io 2023-09-16T23:29:54+00:00 df870d47d2afb03ce0f7c0e3501f7a7cf3632ca9 [ Upstream commit 23c9519def98ee0fa97ea5871535e9b136f522fc ] find_energy_efficient_cpu() bails out early if effective util of the task is 0 as the delta at this point will be zero and there's nothing for EAS to do. When uclamp is being used, this could lead to wrong decisions when uclamp_max is set to 0. In this case the task is capped to performance point 0, but it is actually running and consuming energy and we can benefit from EAS energy calculations. Rework the condition so that it bails out when both util and uclamp_min are 0. We can do that without needing to use uclamp_task_util(); remove it. Fixes: d81304bc6193 ("sched/uclamp: Cater for uclamp in find_energy_efficient_cpu()'s early exit condition") Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20230916232955.2099394-3-qyousef@layalina.io Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 23c9519def98ee0fa97ea5871535e9b136f522fc ]

find_energy_efficient_cpu() bails out early if effective util of the
task is 0 as the delta at this point will be zero and there's nothing
for EAS to do. When uclamp is being used, this could lead to wrong
decisions when uclamp_max is set to 0. In this case the task is capped
to performance point 0, but it is actually running and consuming energy
and we can benefit from EAS energy calculations.

Rework the condition so that it bails out when both util and uclamp_min
are 0.

We can do that without needing to use uclamp_task_util(); remove it.

Fixes: d81304bc6193 ("sched/uclamp: Cater for uclamp in find_energy_efficient_cpu()'s early exit condition")
Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20230916232955.2099394-3-qyousef@layalina.io
Signed-off-by: Sasha Levin <sashal@kernel.org>
sched/uclamp: Set max_spare_cap_cpu even if max_spare_cap is 0 2023-11-20T10:51:49+00:00 Qais Yousef qyousef@layalina.io 2023-09-16T23:29:53+00:00 d77530a1d47fee1cb0c4142a79a26705ce66de01 [ Upstream commit 6b00a40147653c8ea748e8f4396510f252763364 ] When uclamp_max is being used, the util of the task could be higher than the spare capacity of the CPU, but due to uclamp_max value we force-fit it there. The way the condition for checking for max_spare_cap in find_energy_efficient_cpu() was constructed; it ignored any CPU that has its spare_cap less than or _equal_ to max_spare_cap. Since we initialize max_spare_cap to 0; this lead to never setting max_spare_cap_cpu and hence ending up never performing compute_energy() for this cluster and missing an opportunity for a better energy efficient placement to honour uclamp_max setting. max_spare_cap = 0; cpu_cap = capacity_of(cpu) - cpu_util(p); // 0 if cpu_util(p) is high ... util_fits_cpu(...); // will return true if uclamp_max forces it to fit ... // this logic will fail to update max_spare_cap_cpu if cpu_cap is 0 if (cpu_cap > max_spare_cap) { max_spare_cap = cpu_cap; max_spare_cap_cpu = cpu; } prev_spare_cap suffers from a similar problem. Fix the logic by converting the variables into long and treating -1 value as 'not populated' instead of 0 which is a viable and correct spare capacity value. We need to be careful signed comparison is used when comparing with cpu_cap in one of the conditions. Fixes: 1d42509e475c ("sched/fair: Make EAS wakeup placement consider uclamp restrictions") Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20230916232955.2099394-2-qyousef@layalina.io Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 6b00a40147653c8ea748e8f4396510f252763364 ]

When uclamp_max is being used, the util of the task could be higher than
the spare capacity of the CPU, but due to uclamp_max value we force-fit
it there.

The way the condition for checking for max_spare_cap in
find_energy_efficient_cpu() was constructed; it ignored any CPU that has
its spare_cap less than or _equal_ to max_spare_cap. Since we initialize
max_spare_cap to 0; this lead to never setting max_spare_cap_cpu and
hence ending up never performing compute_energy() for this cluster and
missing an opportunity for a better energy efficient placement to honour
uclamp_max setting.

	max_spare_cap = 0;
	cpu_cap = capacity_of(cpu) - cpu_util(p);  // 0 if cpu_util(p) is high

	...

	util_fits_cpu(...);		// will return true if uclamp_max forces it to fit

	...

	// this logic will fail to update max_spare_cap_cpu if cpu_cap is 0
	if (cpu_cap > max_spare_cap) {
		max_spare_cap = cpu_cap;
		max_spare_cap_cpu = cpu;
	}

prev_spare_cap suffers from a similar problem.

Fix the logic by converting the variables into long and treating -1
value as 'not populated' instead of 0 which is a viable and correct
spare capacity value. We need to be careful signed comparison is used
when comparing with cpu_cap in one of the conditions.

Fixes: 1d42509e475c ("sched/fair: Make EAS wakeup placement consider uclamp restrictions")
Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20230916232955.2099394-2-qyousef@layalina.io
Signed-off-by: Sasha Levin <sashal@kernel.org>
sched/fair: Fix cfs_rq_is_decayed() on !SMP 2023-11-20T10:51:49+00:00 Chengming Zhou zhouchengming@bytedance.com 2023-09-13T13:20:31+00:00 42bed989f0efe95f7b4c666cd6879e4c0ac5d1d5 [ Upstream commit c0490bc9bb62d9376f3dd4ec28e03ca0fef97152 ] We don't need to maintain per-queue leaf_cfs_rq_list on !SMP, since it's used for cfs_rq load tracking & balancing on SMP. But sched debug interface uses it to print per-cfs_rq stats. This patch fixes the !SMP version of cfs_rq_is_decayed(), so the per-queue leaf_cfs_rq_list is also maintained correctly on !SMP, to fix the warning in assert_list_leaf_cfs_rq(). Fixes: 0a00a354644e ("sched/fair: Delete useless condition in tg_unthrottle_up()") Reported-by: Leo Yu-Chi Liang <ycliang@andestech.com> Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Tested-by: Leo Yu-Chi Liang <ycliang@andestech.com> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Closes: https://lore.kernel.org/all/ZN87UsqkWcFLDxea@swlinux02/ Link: https://lore.kernel.org/r/20230913132031.2242151-1-chengming.zhou@linux.dev Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit c0490bc9bb62d9376f3dd4ec28e03ca0fef97152 ]

We don't need to maintain per-queue leaf_cfs_rq_list on !SMP, since
it's used for cfs_rq load tracking & balancing on SMP.

But sched debug interface uses it to print per-cfs_rq stats.

This patch fixes the !SMP version of cfs_rq_is_decayed(), so the
per-queue leaf_cfs_rq_list is also maintained correctly on !SMP,
to fix the warning in assert_list_leaf_cfs_rq().

Fixes: 0a00a354644e ("sched/fair: Delete useless condition in tg_unthrottle_up()")
Reported-by: Leo Yu-Chi Liang <ycliang@andestech.com>
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Leo Yu-Chi Liang <ycliang@andestech.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Closes: https://lore.kernel.org/all/ZN87UsqkWcFLDxea@swlinux02/
Link: https://lore.kernel.org/r/20230913132031.2242151-1-chengming.zhou@linux.dev
Signed-off-by: Sasha Levin <sashal@kernel.org>
sched/fair: Remove capacity inversion detection 2023-08-23T15:52:41+00:00 Vincent Guittot vincent.guittot@linaro.org 2023-02-01T14:36:28+00:00 8517d739923e054d774d6004e1c60e9793588502 commit a2e90611b9f425adbbfcdaa5b5e49958ddf6f61b upstream. Remove the capacity inversion detection which is now handled by util_fits_cpu() returning -1 when we need to continue to look for a potential CPU with better performance. This ends up almost reverting patches below except for some comments: commit da07d2f9c153 ("sched/fair: Fixes for capacity inversion detection") commit aa69c36f31aa ("sched/fair: Consider capacity inversion in util_fits_cpu()") commit 44c7b80bffc3 ("sched/fair: Detect capacity inversion") Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20230201143628.270912-3-vincent.guittot@linaro.org Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit a2e90611b9f425adbbfcdaa5b5e49958ddf6f61b upstream.

Remove the capacity inversion detection which is now handled by
util_fits_cpu() returning -1 when we need to continue to look for a
potential CPU with better performance.

This ends up almost reverting patches below except for some comments:
commit da07d2f9c153 ("sched/fair: Fixes for capacity inversion detection")
commit aa69c36f31aa ("sched/fair: Consider capacity inversion in util_fits_cpu()")
commit 44c7b80bffc3 ("sched/fair: Detect capacity inversion")

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20230201143628.270912-3-vincent.guittot@linaro.org
Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
sched/fair: unlink misfit task from cpu overutilized 2023-08-23T15:52:41+00:00 Vincent Guittot vincent.guittot@linaro.org 2023-02-01T14:36:27+00:00 e8acf9971fbe52b7e22d458edb843649d6206565 commit e5ed0550c04c5469ecdc1634d8aa18c8609590f0 upstream. By taking into account uclamp_min, the 1:1 relation between task misfit and cpu overutilized is no more true as a task with a small util_avg may not fit a high capacity cpu because of uclamp_min constraint. Add a new state in util_fits_cpu() to reflect the case that task would fit a CPU except for the uclamp_min hint which is a performance requirement. Use -1 to reflect that a CPU doesn't fit only because of uclamp_min so we can use this new value to take additional action to select the best CPU that doesn't match uclamp_min hint. When util_fits_cpu() returns -1, we will continue to look for a possible CPU with better performance, which replaces Capacity Inversion detection with capacity_orig_of() - thermal_load_avg to detect a capacity inversion. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Reviewed-and-tested-by: Qais Yousef <qyousef@layalina.io> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Tested-by: Kajetan Puchalski <kajetan.puchalski@arm.com> Link: https://lore.kernel.org/r/20230201143628.270912-2-vincent.guittot@linaro.org Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit e5ed0550c04c5469ecdc1634d8aa18c8609590f0 upstream.

By taking into account uclamp_min, the 1:1 relation between task misfit
and cpu overutilized is no more true as a task with a small util_avg may
not fit a high capacity cpu because of uclamp_min constraint.

Add a new state in util_fits_cpu() to reflect the case that task would fit
a CPU except for the uclamp_min hint which is a performance requirement.

Use -1 to reflect that a CPU doesn't fit only because of uclamp_min so we
can use this new value to take additional action to select the best CPU
that doesn't match uclamp_min hint.

When util_fits_cpu() returns -1, we will continue to look for a possible
CPU with better performance, which replaces Capacity Inversion detection
with capacity_orig_of() - thermal_load_avg to detect a capacity inversion.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-and-tested-by: Qais Yousef <qyousef@layalina.io>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Kajetan Puchalski <kajetan.puchalski@arm.com>
Link: https://lore.kernel.org/r/20230201143628.270912-2-vincent.guittot@linaro.org
Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
sched/fair: Use recent_used_cpu to test p->cpus_ptr 2023-07-27T06:50:37+00:00 Miaohe Lin linmiaohe@huawei.com 2023-06-20T08:07:47+00:00 45f739e8fb345cc4352da091602660f94320431f [ Upstream commit ae2ad293d6be143ad223f5f947cca07bcbe42595 ] When checking whether a recently used CPU can be a potential idle candidate, recent_used_cpu should be used to test p->cpus_ptr as p->recent_used_cpu is not equal to recent_used_cpu and candidate decision is made based on recent_used_cpu here. Fixes: 89aafd67f28c ("sched/fair: Use prev instead of new target as recent_used_cpu") Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Phil Auld <pauld@redhat.com> Acked-by: Mel Gorman <mgorman@suse.de> Link: https://lore.kernel.org/r/20230620080747.359122-1-linmiaohe@huawei.com Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit ae2ad293d6be143ad223f5f947cca07bcbe42595 ]

When checking whether a recently used CPU can be a potential idle
candidate, recent_used_cpu should be used to test p->cpus_ptr as
p->recent_used_cpu is not equal to recent_used_cpu and candidate
decision is made based on recent_used_cpu here.

Fixes: 89aafd67f28c ("sched/fair: Use prev instead of new target as recent_used_cpu")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Phil Auld <pauld@redhat.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lore.kernel.org/r/20230620080747.359122-1-linmiaohe@huawei.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
sched/fair: Don't balance task to its current running CPU 2023-07-27T06:50:34+00:00 Yicong Yang yangyicong@hisilicon.com 2023-05-30T08:25:07+00:00 78a5f711efceb37e32c48cd6b40addb671fea9cc [ Upstream commit 0dd37d6dd33a9c23351e6115ae8cdac7863bc7de ] We've run into the case that the balancer tries to balance a migration disabled task and trigger the warning in set_task_cpu() like below: ------------[ cut here ]------------ WARNING: CPU: 7 PID: 0 at kernel/sched/core.c:3115 set_task_cpu+0x188/0x240 Modules linked in: hclgevf xt_CHECKSUM ipt_REJECT nf_reject_ipv4 <...snip> CPU: 7 PID: 0 Comm: swapper/7 Kdump: loaded Tainted: G O 6.1.0-rc4+ #1 Hardware name: Huawei TaiShan 2280 V2/BC82AMDC, BIOS 2280-V2 CS V5.B221.01 12/09/2021 pstate: 604000c9 (nZCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : set_task_cpu+0x188/0x240 lr : load_balance+0x5d0/0xc60 sp : ffff80000803bc70 x29: ffff80000803bc70 x28: ffff004089e190e8 x27: ffff004089e19040 x26: ffff007effcabc38 x25: 0000000000000000 x24: 0000000000000001 x23: ffff80000803be84 x22: 000000000000000c x21: ffffb093e79e2a78 x20: 000000000000000c x19: ffff004089e19040 x18: 0000000000000000 x17: 0000000000001fad x16: 0000000000000030 x15: 0000000000000000 x14: 0000000000000003 x13: 0000000000000000 x12: 0000000000000000 x11: 0000000000000001 x10: 0000000000000400 x9 : ffffb093e4cee530 x8 : 00000000fffffffe x7 : 0000000000ce168a x6 : 000000000000013e x5 : 00000000ffffffe1 x4 : 0000000000000001 x3 : 0000000000000b2a x2 : 0000000000000b2a x1 : ffffb093e6d6c510 x0 : 0000000000000001 Call trace: set_task_cpu+0x188/0x240 load_balance+0x5d0/0xc60 rebalance_domains+0x26c/0x380 _nohz_idle_balance.isra.0+0x1e0/0x370 run_rebalance_domains+0x6c/0x80 __do_softirq+0x128/0x3d8 ____do_softirq+0x18/0x24 call_on_irq_stack+0x2c/0x38 do_softirq_own_stack+0x24/0x3c __irq_exit_rcu+0xcc/0xf4 irq_exit_rcu+0x18/0x24 el1_interrupt+0x4c/0xe4 el1h_64_irq_handler+0x18/0x2c el1h_64_irq+0x74/0x78 arch_cpu_idle+0x18/0x4c default_idle_call+0x58/0x194 do_idle+0x244/0x2b0 cpu_startup_entry+0x30/0x3c secondary_start_kernel+0x14c/0x190 __secondary_switched+0xb0/0xb4 ---[ end trace 0000000000000000 ]--- Further investigation shows that the warning is superfluous, the migration disabled task is just going to be migrated to its current running CPU. This is because that on load balance if the dst_cpu is not allowed by the task, we'll re-select a new_dst_cpu as a candidate. If no task can be balanced to dst_cpu we'll try to balance the task to the new_dst_cpu instead. In this case when the migration disabled task is not on CPU it only allows to run on its current CPU, load balance will select its current CPU as new_dst_cpu and later triggers the warning above. The new_dst_cpu is chosen from the env->dst_grpmask. Currently it contains CPUs in sched_group_span() and if we have overlapped groups it's possible to run into this case. This patch makes env->dst_grpmask of group_balance_mask() which exclude any CPUs from the busiest group and solve the issue. For balancing in a domain with no overlapped groups the behaviour keeps same as before. Suggested-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Yicong Yang <yangyicong@hisilicon.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Link: https://lore.kernel.org/r/20230530082507.10444-1-yangyicong@huawei.com Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 0dd37d6dd33a9c23351e6115ae8cdac7863bc7de ]

We've run into the case that the balancer tries to balance a migration
disabled task and trigger the warning in set_task_cpu() like below:

 ------------[ cut here ]------------
 WARNING: CPU: 7 PID: 0 at kernel/sched/core.c:3115 set_task_cpu+0x188/0x240
 Modules linked in: hclgevf xt_CHECKSUM ipt_REJECT nf_reject_ipv4 <...snip>
 CPU: 7 PID: 0 Comm: swapper/7 Kdump: loaded Tainted: G           O       6.1.0-rc4+ #1
 Hardware name: Huawei TaiShan 2280 V2/BC82AMDC, BIOS 2280-V2 CS V5.B221.01 12/09/2021
 pstate: 604000c9 (nZCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
 pc : set_task_cpu+0x188/0x240
 lr : load_balance+0x5d0/0xc60
 sp : ffff80000803bc70
 x29: ffff80000803bc70 x28: ffff004089e190e8 x27: ffff004089e19040
 x26: ffff007effcabc38 x25: 0000000000000000 x24: 0000000000000001
 x23: ffff80000803be84 x22: 000000000000000c x21: ffffb093e79e2a78
 x20: 000000000000000c x19: ffff004089e19040 x18: 0000000000000000
 x17: 0000000000001fad x16: 0000000000000030 x15: 0000000000000000
 x14: 0000000000000003 x13: 0000000000000000 x12: 0000000000000000
 x11: 0000000000000001 x10: 0000000000000400 x9 : ffffb093e4cee530
 x8 : 00000000fffffffe x7 : 0000000000ce168a x6 : 000000000000013e
 x5 : 00000000ffffffe1 x4 : 0000000000000001 x3 : 0000000000000b2a
 x2 : 0000000000000b2a x1 : ffffb093e6d6c510 x0 : 0000000000000001
 Call trace:
  set_task_cpu+0x188/0x240
  load_balance+0x5d0/0xc60
  rebalance_domains+0x26c/0x380
  _nohz_idle_balance.isra.0+0x1e0/0x370
  run_rebalance_domains+0x6c/0x80
  __do_softirq+0x128/0x3d8
  ____do_softirq+0x18/0x24
  call_on_irq_stack+0x2c/0x38
  do_softirq_own_stack+0x24/0x3c
  __irq_exit_rcu+0xcc/0xf4
  irq_exit_rcu+0x18/0x24
  el1_interrupt+0x4c/0xe4
  el1h_64_irq_handler+0x18/0x2c
  el1h_64_irq+0x74/0x78
  arch_cpu_idle+0x18/0x4c
  default_idle_call+0x58/0x194
  do_idle+0x244/0x2b0
  cpu_startup_entry+0x30/0x3c
  secondary_start_kernel+0x14c/0x190
  __secondary_switched+0xb0/0xb4
 ---[ end trace 0000000000000000 ]---

Further investigation shows that the warning is superfluous, the migration
disabled task is just going to be migrated to its current running CPU.
This is because that on load balance if the dst_cpu is not allowed by the
task, we'll re-select a new_dst_cpu as a candidate. If no task can be
balanced to dst_cpu we'll try to balance the task to the new_dst_cpu
instead. In this case when the migration disabled task is not on CPU it
only allows to run on its current CPU, load balance will select its
current CPU as new_dst_cpu and later triggers the warning above.

The new_dst_cpu is chosen from the env->dst_grpmask. Currently it
contains CPUs in sched_group_span() and if we have overlapped groups it's
possible to run into this case. This patch makes env->dst_grpmask of
group_balance_mask() which exclude any CPUs from the busiest group and
solve the issue. For balancing in a domain with no overlapped groups
the behaviour keeps same as before.

Suggested-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20230530082507.10444-1-yangyicong@huawei.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
sched/fair: Fix inaccurate tally of ttwu_move_affine 2023-05-11T14:03:31+00:00 Libo Chen libo.chen@oracle.com 2022-08-10T22:33:13+00:00 944465c772fb00509150ba374298d9e4d5d47788 [ Upstream commit 39afe5d6fc59237ff7738bf3ede5a8856822d59d ] There are scenarios where non-affine wakeups are incorrectly counted as affine wakeups by schedstats. When wake_affine_idle() returns prev_cpu which doesn't equal to nr_cpumask_bits, it will slip through the check: target == nr_cpumask_bits in wake_affine() and be counted as if target == this_cpu in schedstats. Replace target == nr_cpumask_bits with target != this_cpu to make sure affine wakeups are accurately tallied. Fixes: 806486c377e33 (sched/fair: Do not migrate if the prev_cpu is idle) Suggested-by: Daniel Jordan <daniel.m.jordan@oracle.com> Signed-off-by: Libo Chen <libo.chen@oracle.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com> Link: https://lore.kernel.org/r/20220810223313.386614-1-libo.chen@oracle.com Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 39afe5d6fc59237ff7738bf3ede5a8856822d59d ]

There are scenarios where non-affine wakeups are incorrectly counted as
affine wakeups by schedstats.

When wake_affine_idle() returns prev_cpu which doesn't equal to
nr_cpumask_bits, it will slip through the check: target == nr_cpumask_bits
in wake_affine() and be counted as if target == this_cpu in schedstats.

Replace target == nr_cpumask_bits with target != this_cpu to make sure
affine wakeups are accurately tallied.

Fixes: 806486c377e33 (sched/fair: Do not migrate if the prev_cpu is idle)
Suggested-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: Libo Chen <libo.chen@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Link: https://lore.kernel.org/r/20220810223313.386614-1-libo.chen@oracle.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
sched/fair: Fixes for capacity inversion detection 2023-04-26T12:28:42+00:00 Qais Yousef qyousef@layalina.io 2023-04-18T14:04:54+00:00 d362a03d920edc0bb9a85c5150ef4ff5fd365c72 commit: da07d2f9c153e457e845d4dcfdd13568d71d18a4 upstream. Traversing the Perf Domains requires rcu_read_lock() to be held and is conditional on sched_energy_enabled(). Ensure right protections applied. Also skip capacity inversion detection for our own pd; which was an error. Fixes: 44c7b80bffc3 ("sched/fair: Detect capacity inversion") Reported-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Link: https://lore.kernel.org/r/20230112122708.330667-3-qyousef@layalina.io (cherry picked from commit da07d2f9c153e457e845d4dcfdd13568d71d18a4) Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit: da07d2f9c153e457e845d4dcfdd13568d71d18a4 upstream.

Traversing the Perf Domains requires rcu_read_lock() to be held and is
conditional on sched_energy_enabled(). Ensure right protections applied.

Also skip capacity inversion detection for our own pd; which was an
error.

Fixes: 44c7b80bffc3 ("sched/fair: Detect capacity inversion")
Reported-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20230112122708.330667-3-qyousef@layalina.io
(cherry picked from commit da07d2f9c153e457e845d4dcfdd13568d71d18a4)
Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>