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sched/core: Don't steal a proxy-exec donor

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try_steal_cookie() avoids stealing src->core_pick and src->curr before
moving a task with the same cookie via move_queued_task_locked().

With proxy-exec, src->donor is the current scheduling context and may
differ from src->curr. Stealing it migrates a task that the source rq
still treats as current, leaving src's scheduler state for that task
stale. For CFS this means cfs_rq->curr points at the stolen entity,
and the next pick on the source rq hits the WARN_ON_ONCE in
put_prev_entity().

Commit 7de9d4f946 ("sched: Start blocked_on chain processing in
find_proxy_task()") tweaked the fair class logic so that the donor task
isn't migrated away while we're running the proxy. Do it similarly for
try_steal_cookie() and skip src->donor as well.

Fixes: 7de9d4f946 ("sched: Start blocked_on chain processing in find_proxy_task()")
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: John Stultz <jstultz@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260807035232.1881495-3-jstultz@google.com
This commit is contained in:
Vasily Gorbik 2026-08-07 03:52:08 +00:00 committed by Peter Zijlstra
parent f0d243a96f
commit 3dd95f0773
1 changed files with 1 additions and 1 deletions
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2
kernel/sched/core.c
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@ -6509,7 +6509,7 @@ static bool try_steal_cookie(int this, int that)
return false;
do {
if (p == src->core_pick || p == src->curr)
if (p == src->core_pick || p == src->curr || p == src->donor)
goto next;
if (!is_cpu_allowed(p, this))