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>
diff --git a/include/linux/sem.h b/include/linux/sem.h
index 8a4adbef..f2961af 100644
--- a/include/linux/sem.h
+++ b/include/linux/sem.h
@@ -79,6 +79,7 @@
#ifdef __KERNEL__
#include <asm/atomic.h>
#include <linux/rcupdate.h>
+#include <linux/cache.h>
struct task_struct;
@@ -91,7 +92,8 @@
/* 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 */