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authorManfred Spraul <manfred@colorfullife.com>2013-09-30 13:45:25 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-09-30 14:31:03 -0700
commit0e8c665699e953fa58dc1b0b0d09e5dce7343cc7 (patch)
tree43f6f73159d7be2fbd7930315a053e27c4c8d189 /ipc
parentfb31ba30fb10fe0ee11739f51669d581b4a1412c (diff)
downloadlinux-0e8c665699e953fa58dc1b0b0d09e5dce7343cc7.tar.gz
ipc/sem.c: update sem_otime for all operations
In commit 0a2b9d4c7967 ("ipc/sem.c: move wake_up_process out of the spinlock section"), the update of semaphore's sem_otime(last semop time) was moved to one central position (do_smart_update). But since do_smart_update() is only called for operations that modify the array, this means that wait-for-zero semops do not update sem_otime anymore. The fix is simple: Non-alter operations must update sem_otime. [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Manfred Spraul <manfred@colorfullife.com> Reported-by: Jia He <jiakernel@gmail.com> Tested-by: Jia He <jiakernel@gmail.com> Cc: Davidlohr Bueso <davidlohr.bueso@hp.com> Cc: Mike Galbraith <efault@gmx.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'ipc')
-rw-r--r--ipc/sem.c42
1 files changed, 29 insertions, 13 deletions
diff --git a/ipc/sem.c b/ipc/sem.c
index cd6a733011a..8c4f59b0204 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -918,6 +918,24 @@ again:
}
/**
+ * set_semotime(sma, sops) - set sem_otime
+ * @sma: semaphore array
+ * @sops: operations that modified the array, may be NULL
+ *
+ * sem_otime is replicated to avoid cache line trashing.
+ * This function sets one instance to the current time.
+ */
+static void set_semotime(struct sem_array *sma, struct sembuf *sops)
+{
+ if (sops == NULL) {
+ sma->sem_base[0].sem_otime = get_seconds();
+ } else {
+ sma->sem_base[sops[0].sem_num].sem_otime =
+ get_seconds();
+ }
+}
+
+/**
* do_smart_update(sma, sops, nsops, otime, pt) - optimized update_queue
* @sma: semaphore array
* @sops: operations that were performed
@@ -967,17 +985,10 @@ static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsop
}
}
}
- if (otime) {
- if (sops == NULL) {
- sma->sem_base[0].sem_otime = get_seconds();
- } else {
- sma->sem_base[sops[0].sem_num].sem_otime =
- get_seconds();
- }
- }
+ if (otime)
+ set_semotime(sma, sops);
}
-
/* The following counts are associated to each semaphore:
* semncnt number of tasks waiting on semval being nonzero
* semzcnt number of tasks waiting on semval being zero
@@ -1839,12 +1850,17 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
error = perform_atomic_semop(sma, sops, nsops, un,
task_tgid_vnr(current));
- if (error <= 0) {
- if (alter && error == 0)
+ if (error == 0) {
+ /* If the operation was successful, then do
+ * the required updates.
+ */
+ if (alter)
do_smart_update(sma, sops, nsops, 1, &tasks);
-
- goto out_unlock_free;
+ else
+ set_semotime(sma, sops);
}
+ if (error <= 0)
+ goto out_unlock_free;
/* We need to sleep on this operation, so we put the current
* task into the pending queue and go to sleep.