[PATCH 3/3] [PATCH] ipc/sem.c: cacheline align the ipc spinlock for semaphores

[Manfred Spraul <manfred@colorfullife.com>]

This patch cacheline aligns 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>
---
 include/linux/sem.h |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/include/linux/sem.h b/include/linux/sem.h
index 8a4adbe..f2961af 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 */
-- 
1.6.6.1