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>

1 files changed, 29 insertions, 13 deletions

diff --git a/ipc/sem.c b/ipc/sem.c
index cd6a733011a2..8c4f59b0204a 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.