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authorManfred Spraul <manfred@colorfullife.com>2010-05-26 14:43:42 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-05-27 09:12:49 -0700
commit31a7c4746e9925512afab30557dd445d677cc802 (patch)
tree7f7b39331aa51b77c159b046d406b12aec24de11
parent0a2b9d4c79671b05956806ede5d054e03ae56280 (diff)
downloadvexpress-lsk-31a7c4746e9925512afab30557dd445d677cc802.tar.gz
ipc/sem.c: cacheline align the ipc spinlock for semaphores
Cacheline align the spinlock for sysv semaphores. Without the patch, the spinlock and sem_otime [written by every semop that modified the array] and sem_base [read in the hot path of try_atomic_semop()] can be in the same cacheline. Signed-off-by: Manfred Spraul <manfred@colorfullife.com> Cc: Chris Mason <chris.mason@oracle.com> Cc: Zach Brown <zach.brown@oracle.com> Cc: Jens Axboe <jens.axboe@oracle.com> Cc: Nick Piggin <npiggin@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--include/linux/sem.h4
1 files changed, 3 insertions, 1 deletions
diff --git a/include/linux/sem.h b/include/linux/sem.h
index 8a4adbef8a0..f2961afa2f6 100644
--- a/include/linux/sem.h
+++ b/include/linux/sem.h
@@ -79,6 +79,7 @@ struct seminfo {
#ifdef __KERNEL__
#include <asm/atomic.h>
#include <linux/rcupdate.h>
+#include <linux/cache.h>
struct task_struct;
@@ -91,7 +92,8 @@ struct sem {
/* One sem_array data structure for each set of semaphores in the system. */
struct sem_array {
- struct kern_ipc_perm sem_perm; /* permissions .. see ipc.h */
+ struct kern_ipc_perm ____cacheline_aligned_in_smp
+ sem_perm; /* permissions .. see ipc.h */
time_t sem_otime; /* last semop time */
time_t sem_ctime; /* last change time */
struct sem *sem_base; /* ptr to first semaphore in array */