Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | From | Daniel Vacek <> | Subject | [PATCH] sched/core: fix affine_move_task failure case | Date | Mon, 18 Mar 2024 12:17:48 +0100 |
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Bill Peters reported CPU hangs while offlining/onlining CPUs on s390.
Analyzing the vmcore data shows `stop_one_cpu_nowait()` in `affine_move_task()` can fail when racing with off-/on-lining resulting in a deadlock waiting for the pending migration stop work completion which is never done.
Fix this by correctly handling such a condition.
Fixes: 9e81889c7648 ("sched: Fix affine_move_task() self-concurrency") Cc: stable@vger.kernel.org Reported-by: Bill Peters <wpeters@atpco.net> Tested-by: Bill Peters <wpeters@atpco.net> Signed-off-by: Daniel Vacek <neelx@redhat.com> --- kernel/sched/core.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 9116bcc903467..d0ff5c611a1c8 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3069,8 +3069,17 @@ static int affine_move_task(struct rq *rq, struct task_struct *p, struct rq_flag preempt_disable(); task_rq_unlock(rq, p, rf); if (!stop_pending) { - stop_one_cpu_nowait(cpu_of(rq), migration_cpu_stop, - &pending->arg, &pending->stop_work); + stop_pending = + stop_one_cpu_nowait(cpu_of(rq), migration_cpu_stop, + &pending->arg, &pending->stop_work); + + if (!stop_pending) { + rq = task_rq_lock(p, rf); + pending->stop_pending = false; + p->migration_pending = NULL; + task_rq_unlock(rq, p, rf); + complete_all(&pending->done); + } } preempt_enable(); -- 2.43.0
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