Subject: + ipc-semc-update-sem_otime-for-all-operations.patch added to -mm tree
To: manfred@xxxxxxxxxxxxxxxx,davidlohr.bueso@xxxxxx,efault@xxxxxx,jiakernel@xxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Thu, 26 Sep 2013 14:06:11 -0700
The patch titled
Subject: ipc/sem.c: update sem_otime for all operations
has been added to the -mm tree. Its filename is
ipc-semc-update-sem_otime-for-all-operations.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/ipc-semc-update-sem_otime-for-all-operations.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/ipc-semc-update-sem_otime-for-all-operations.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
Subject: ipc/sem.c: update sem_otime for all operations
In 0a2b9d4c ("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.
Signed-off-by: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
Reported-by: Jia He <jiakernel@xxxxxxxxx>
Tested-by: Jia He <jiakernel@xxxxxxxxx>
Cc: Davidlohr Bueso <davidlohr.bueso@xxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
ipc/sem.c | 41 +++++++++++++++++++++++++++++------------
1 file changed, 29 insertions(+), 12 deletions(-)
diff -puN ipc/sem.c~ipc-semc-update-sem_otime-for-all-operations ipc/sem.c
--- a/ipc/sem.c~ipc-semc-update-sem_otime-for-all-operations
+++ a/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_a
}
}
}
- 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
@@ -1839,10 +1850,16 @@ SYSCALL_DEFINE4(semtimedop, int, semid,
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);
-
+ else
+ set_semotime(sma, sops);
+ }
+ if (error <= 0) {
goto out_unlock_free;
}
_
Patches currently in -mm which might be from manfred@xxxxxxxxxxxxxxxx are
origin.patch
ipc-semc-fix-race-in-sem_lock.patch
ipc-semc-optimize-sem_lock.patch
ipc-semc-synchronize-the-proc-interface.patch
ipc-semc-update-sem_otime-for-all-operations.patch
slab-leaks3-default-y.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
