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sched/wait: Avoid modifying entry on failed priority registration

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add_wait_queue_priority_exclusive() sets WQ_FLAG_EXCLUSIVE and
WQ_FLAG_PRIORITY before checking whether another priority waiter is
already present. Thus, when registration fails with -EBUSY, the entry
is left unqueued but with modified flags.

There is no need to modify the entry before the failure check. Move the
flag update after the check so that a rejected registration does not
unnecessarily alter the entry.

Signed-off-by: Hui Su <sh_def@163.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Link: https://patch.msgid.link/20261011015019.4056529-1-sh_def@163.com
This commit is contained in:
Hui Su authored and Peter Zijlstra committed 2026-10-13 13:51:28 +02:00
1 parent cc459ecd93
commit 159b172906
1 file changed
+1 -2
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kernel/sched/wait.c
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@@ -54,14 +54,13 @@ int add_wait_queue_priority_exclusive(struct wait_queue_head *wq_head,
{
struct list_head *head = &wq_head->head;
wq_entry->flags |= WQ_FLAG_EXCLUSIVE | WQ_FLAG_PRIORITY;
guard(spinlock_irqsave)(&wq_head->lock);
if (!list_empty(head) &&
(list_first_entry(head, typeof(*wq_entry), entry)->flags & WQ_FLAG_PRIORITY))
return -EBUSY;
wq_entry->flags |= WQ_FLAG_EXCLUSIVE | WQ_FLAG_PRIORITY;
list_add(&wq_entry->entry, head);
return 0;
}