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ipc/sem.c: bugfix for semop() not reporting successful operation
The last change to improve the scalability moved the actual wake-up out of the section that is protected by spin_lock(sma->sem_perm.lock). This means that IN_WAKEUP can be in queue.status even when the spinlock is acquired by the current task. Thus the same loop that is performed when queue.status is read without the spinlock acquired must be performed when the spinlock is acquired. Thanks to email@example.com for noticing lack of the memory barrier. Addresses https://bugzilla.kernel.org/show_bug.cgi?id=16255 [firstname.lastname@example.org: clean up kerneldoc, checkpatch warning and whitespace] Signed-off-by: Manfred Spraul <email@example.com> Reported-by: Luca Tettamanti <firstname.lastname@example.org> Tested-by: Luca Tettamanti <email@example.com> Reported-by: Christoph Lameter <firstname.lastname@example.org> Cc: Maciej Rutecki <email@example.com> Cc: KAMEZAWA Hiroyuki <firstname.lastname@example.org> Signed-off-by: Andrew Morton <email@example.com> Signed-off-by: Linus Torvalds <firstname.lastname@example.org>
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