linux/kernel/sched
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
..
autogroup.c sched/autogroup: Fix sysctl move 2022-05-30 12:36:36 +02:00
autogroup.h sched/headers: Add header guard to kernel/sched/stats.h and kernel/sched/autogroup.h 2022-02-23 08:22:00 +01:00
build_policy.c sched: Fix missing prototype warnings 2022-05-01 10:03:43 +02:00
build_utility.c sched: Fix missing prototype warnings 2022-05-01 10:03:43 +02:00
clock.c sched/clock: Use try_cmpxchg64 in sched_clock_{local,remote} 2022-05-19 23:46:09 +02:00
completion.c sched/headers: Introduce kernel/sched/build_utility.c and build multiple .c files there 2022-02-23 10:58:33 +01:00
core_sched.c sched/core: Fix the bug that task won't enqueue into core tree when update cookie 2022-07-21 10:39:39 +02:00
core.c sched/core: Do not requeue task on CPU excluded from cpus_mask 2022-08-04 11:26:13 +02:00
cpuacct.c Merge branch 'sched/fast-headers' into sched/core 2022-03-15 09:05:05 +01:00
cpudeadline.c sched/headers: Introduce kernel/sched/build_policy.c and build multiple .c files there 2022-02-23 10:58:33 +01:00
cpudeadline.h sched/headers: Simplify and clean up header usage in the scheduler 2018-03-04 12:39:29 +01:00
cpufreq_schedutil.c sched, drivers: Remove max param from effective_cpu_util()/sched_cpu_util() 2022-06-28 09:17:46 +02:00
cpufreq.c sched/headers: Introduce kernel/sched/build_utility.c and build multiple .c files there 2022-02-23 10:58:33 +01:00
cpupri.c sched/headers: Introduce kernel/sched/build_utility.c and build multiple .c files there 2022-02-23 10:58:33 +01:00
cpupri.h sched/cpupri: Add CPUPRI_HIGHER 2020-10-29 11:00:30 +01:00
cputime.c sched/core: add forced idle accounting for cgroups 2022-07-04 09:23:07 +02:00
deadline.c This cycle's scheduler updates for v6.0 are: 2022-08-01 11:49:06 -07:00
debug.c sched/headers: Introduce kernel/sched/build_utility.c and build multiple .c files there 2022-02-23 10:58:33 +01:00
fair.c sched/fair: fix case with reduced capacity CPU 2022-07-13 11:29:17 +02:00
features.h sched/fair: Introduce SIS_UTIL to search idle CPU based on sum of util_avg 2022-06-28 09:08:30 +02:00
idle.c Scheduler changes in this cycle were: 2022-05-24 11:11:13 -07:00
isolation.c sched/headers: Introduce kernel/sched/build_utility.c and build multiple .c files there 2022-02-23 10:58:33 +01:00
loadavg.c sched/headers: Introduce kernel/sched/build_utility.c and build multiple .c files there 2022-02-23 10:58:33 +01:00
Makefile sched/headers: Introduce kernel/sched/build_policy.c and build multiple .c files there 2022-02-23 10:58:33 +01:00
membarrier.c sched/headers: Introduce kernel/sched/build_utility.c and build multiple .c files there 2022-02-23 10:58:33 +01:00
pelt.c sched/headers: Introduce kernel/sched/build_policy.c and build multiple .c files there 2022-02-23 10:58:33 +01:00
pelt.h sched/fair: Decay task PELT values during wakeup migration 2022-06-28 09:17:46 +02:00
psi.c sched/psi: report zeroes for CPU full at the system level 2022-04-22 12:14:08 +02:00
rt.c nohz/full, sched/rt: Fix missed tick-reenabling bug in dequeue_task_rt() 2022-07-21 10:39:38 +02:00
sched-pelt.h sched/fair: Fix "runnable_avg_yN_inv" not used warnings 2019-06-17 12:15:58 +02:00
sched.h sched/rt: Fix Sparse warnings due to undefined rt.c declarations 2022-08-03 11:22:37 +02:00
smp.h smp: Rename flush_smp_call_function_from_idle() 2022-05-01 10:03:43 +02:00
stats.c sched/headers: Introduce kernel/sched/build_utility.c and build multiple .c files there 2022-02-23 10:58:33 +01:00
stats.h sched/headers: Reorganize, clean up and optimize kernel/sched/sched.h dependencies 2022-02-23 10:58:34 +01:00
stop_task.c sched/headers: Introduce kernel/sched/build_utility.c and build multiple .c files there 2022-02-23 10:58:33 +01:00
swait.c sched/headers: Introduce kernel/sched/build_utility.c and build multiple .c files there 2022-02-23 10:58:33 +01:00
topology.c sched/numa: Adjust imb_numa_nr to a better approximation of memory channels 2022-06-13 10:30:00 +02:00
wait_bit.c sched/headers: Introduce kernel/sched/build_utility.c and build multiple .c files there 2022-02-23 10:58:33 +01:00
wait.c sched/headers: Introduce kernel/sched/build_utility.c and build multiple .c files there 2022-02-23 10:58:33 +01:00