The patch titled
Subject: ipc/sem: simplify wait-wake loop
has been removed from the -mm tree. Its filename was
ipc-sem-simplify-wait-wake-loop.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Subject: 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@xxxxxxxxxxxxxxxxxxxx: coding-style fixes]
Link: http://lkml.kernel.org/r/1478708774-28826-2-git-send-email-dave@xxxxxxxxxxxx
Signed-off-by: Davidlohr Bueso <dbueso@xxxxxxx>
Cc: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
ipc/sem.c | 118 +++++++++++++++++++++++++---------------------------
1 file changed, 57 insertions(+), 61 deletions(-)
diff -puN ipc/sem.c~ipc-sem-simplify-wait-wake-loop ipc/sem.c
--- a/ipc/sem.c~ipc-sem-simplify-wait-wake-loop
+++ a/ipc/sem.c
@@ -1963,71 +1963,67 @@ SYSCALL_DEFINE4(semtimedop, int, semid,
sma->complex_count++;
}
-sleep_again:
- queue.status = -EINTR;
- queue.sleeper = current;
-
- __set_current_state(TASK_INTERRUPTIBLE);
- sem_unlock(sma, locknum);
- rcu_read_unlock();
-
- if (timeout)
- jiffies_left = schedule_timeout(jiffies_left);
- else
- 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.
- *
- * 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().
- */
- error = READ_ONCE(queue.status);
- if (error != -EINTR) {
+ do {
+ queue.status = -EINTR;
+ queue.sleeper = current;
+
+ __set_current_state(TASK_INTERRUPTIBLE);
+ sem_unlock(sma, locknum);
+ rcu_read_unlock();
+
+ if (timeout)
+ jiffies_left = schedule_timeout(jiffies_left);
+ else
+ schedule();
+
/*
- * 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.
+ * 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().
*/
- smp_mb();
- goto out_free;
- }
+ 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 userspace stale data that was
+ * overwritten by the previous owner of the semaphore.
+ */
+ smp_mb();
+ goto out_free;
+ }
+
+ rcu_read_lock();
+ sma = sem_obtain_lock(ns, semid, sops, nsops, &locknum);
+ error = READ_ONCE(queue.status);
- rcu_read_lock();
- sma = sem_obtain_lock(ns, semid, sops, nsops, &locknum);
- error = READ_ONCE(queue.status);
-
- /*
- * Array removed? If yes, leave without sem_unlock().
- */
- if (IS_ERR(sma)) {
- rcu_read_unlock();
- goto out_free;
- }
+ /*
+ * Array removed? If yes, leave without sem_unlock().
+ */
+ if (IS_ERR(sma)) {
+ rcu_read_unlock();
+ goto out_free;
+ }
- /*
- * If queue.status != -EINTR we are woken up by another process.
- * Leave without unlink_queue(), but with sem_unlock().
- */
- if (error != -EINTR)
- goto out_unlock_free;
-
- /*
- * If an interrupt occurred we have to clean up the queue.
- */
- if (timeout && jiffies_left == 0)
- error = -EAGAIN;
-
- /*
- * If the wakeup was spurious, just retry.
- */
- if (error == -EINTR && !signal_pending(current))
- goto sleep_again;
+ /*
+ * If queue.status != -EINTR we are woken up by another process.
+ * Leave without unlink_queue(), but with sem_unlock().
+ */
+ if (error != -EINTR)
+ goto out_unlock_free;
+
+ /*
+ * If an interrupt occurred we have to clean up the queue.
+ */
+ if (timeout && jiffies_left == 0)
+ error = -EAGAIN;
+ } while (error == -EINTR && !signal_pending(current)); /* spurious */
unlink_queue(sma, &queue);
_
Patches currently in -mm which might be from dave@xxxxxxxxxxxx are
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