This is a note to let you know that I've just added the patch titled
ipc/sem.c: update sem_otime for all operations
to the 3.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ipc-sem.c-update-sem_otime-for-all-operations.patch
and it can be found in the queue-3.11 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 0e8c665699e953fa58dc1b0b0d09e5dce7343cc7 Mon Sep 17 00:00:00 2001
From: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
Date: Mon, 30 Sep 2013 13:45:25 -0700
Subject: ipc/sem.c: update sem_otime for all operations
From: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
commit 0e8c665699e953fa58dc1b0b0d09e5dce7343cc7 upstream.
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@xxxxxxxxxxxxxxxxxxxx: coding-style fixes]
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>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
ipc/sem.c | 42 +++++++++++++++++++++++++++++-------------
1 file changed, 29 insertions(+), 13 deletions(-)
--- 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_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
@@ -1839,12 +1850,17 @@ 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);
-
- 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.
Patches currently in stable-queue which might be from manfred@xxxxxxxxxxxxxxxx are
queue-3.11/ipc-drop-ipc_lock_by_ptr.patch
queue-3.11/ipc-sem.c-synchronize-the-proc-interface.patch
queue-3.11/ipc-msg-drop-msg_unlock.patch
queue-3.11/ipc-shm-shorten-critical-region-in-shmctl_down.patch
queue-3.11/ipc-rename-ids-rw_mutex.patch
queue-3.11/ipc-shm-introduce-lockless-functions-to-obtain-the-ipc-object.patch
queue-3.11/ipc-sem.c-optimize-sem_lock.patch
queue-3.11/ipc-shm-shorten-critical-region-for-shmat.patch
queue-3.11/ipc-shm-shorten-critical-region-for-shmctl.patch
queue-3.11/ipc-shm-introduce-shmctl_nolock.patch
queue-3.11/ipc-drop-ipcctl_pre_down.patch
queue-3.11/ipc-document-general-ipc-locking-scheme.patch
queue-3.11/ipc-shm-drop-shm_lock_check.patch
queue-3.11/ipc-shm-guard-against-non-existant-vma-in-shmdt-2.patch
queue-3.11/ipc-shm-cleanup-do_shmat-pasta.patch
queue-3.11/ipc-drop-ipc_lock_check.patch
queue-3.11/ipc-sem.c-update-sem_otime-for-all-operations.patch
queue-3.11/ipc-shm-make-shmctl_nolock-lockless.patch
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