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ipc/sem: simplify wait-wake loop 

Instead of using the reverse goto, we can simplify the flow and make it
more language natural by just doing do-while instead.  One would hope
this is the standard way (or obviously just with a while bucle) that we
do wait/wakeup handling in the kernel.  The exact same logic is kept,
just more indented.

[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/1478708774-28826-2-git-send-email-dave@stgolabs.net
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Davidlohr Bueso 2016-12-14 15:06:46 -08:00 committed by Linus Torvalds
parent f150f02cfb
commit b5fa01a22e
1 changed files with 56 additions and 60 deletions
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30
ipc/sem.c
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@ -1963,7 +1963,7 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
sma->complex_count++;
}
sleep_again:
do {
queue.status = -EINTR;
queue.sleeper = current;
@ -1977,22 +1977,23 @@ sleep_again:
schedule();
/*
* fastpath: the semop has completed, either successfully or not, from
* the syscall pov, is quite irrelevant to us at this point; we're done.
* fastpath: the semop has completed, either successfully or
* not, from the syscall pov, is quite irrelevant to us at this
* point; we're done.
*
* We _do_ care, nonetheless, about being awoken by a signal or
* spuriously. The queue.status is checked again in the slowpath (aka
* after taking sem_lock), such that we can detect scenarios where we
* were awakened externally, during the window between wake_q_add() and
* wake_up_q().
* spuriously. The queue.status is checked again in the
* slowpath (aka after taking sem_lock), such that we can detect
* scenarios where we were awakened externally, during the
* window between wake_q_add() and wake_up_q().
*/
error = READ_ONCE(queue.status);
if (error != -EINTR) {
/*
* User space could assume that semop() is a memory barrier:
* Without the mb(), the cpu could speculatively read in user
* space stale data that was overwritten by the previous owner
* of the semaphore.
* User space could assume that semop() is a memory
* barrier: Without the mb(), the cpu could
* speculatively read in userspace stale data that was
* overwritten by the previous owner of the semaphore.
*/
smp_mb();
goto out_free;
@ -2022,12 +2023,7 @@ sleep_again:
*/
if (timeout && jiffies_left == 0)
error = -EAGAIN;
/*
* If the wakeup was spurious, just retry.
*/
if (error == -EINTR && !signal_pending(current))
goto sleep_again;
} while (error == -EINTR && !signal_pending(current)); /* spurious */
unlink_queue(sma, &queue);