sched/core: Avoid false migration warning for proxy donors

Browse source

Proxy execution can move a blocked donor's scheduling context to the
lock owner's CPU even when the donor is migration-disabled. The donor
does not execute there, and its original execution CPU remains recorded
in wake_cpu.

set_task_cpu() warns unconditionally for migration-disabled tasks, so a
subsequent proxy migration or the wakeup path returning the donor home
triggers a false positive: moving a blocked scheduling context does not
violate the migration-disabled execution context.

For example, creating a mutex owner on CPU1 and a migration-disabled
waiter on CPU0 can trigger the following warning:

  proxy_migrate_repro: donor blocking on CPU0 with migration disabled
  proxy_migrate_repro: donor moved from CPU0 to CPU1
  WARNING: kernel/sched/core.c:3389 at set_task_cpu+0x1d3/0x280
  ...
  Call Trace:
   try_to_wake_up+0x43f/0x780
   __mutex_unlock_slowpath+0x330/0x540
   owner_fn+0x9f/0xc0 [proxy_migrate_repro]
  ...
  proxy_migrate_repro: donor woke on CPU0, task_cpu=0
  proxy_migrate_repro: completed

Exclude blocked proxy donors from the warning. The proxy wakeup path
restores an executable placement before clearing the blocked state.

Fixes: b049b81bdf ("sched: Handle blocked-waiter migration (and return migration)")
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: John Stultz <jstultz@google.com>
Link: https://patch.msgid.link/20260915184101.2621252-1-arighi@nvidia.com

...

This commit is contained in:

Andrea Righi 2026-09-15 20:41:01 +02:00 • committed by Peter Zijlstra

parent fd73f4a665

commit fe3c73d7bc

1 changed files with 8 additions and 1 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

9

kernel/sched/core.c

View file