sched/core: Avoid false migration warning for proxy donors

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: b049b81bdff6 ("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

0 files changed, 0 insertions, 0 deletions