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Commit 31a7c474 authored by Manfred Spraul's avatar Manfred Spraul Committed by Linus Torvalds
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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: default avatarManfred 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 0a2b9d4c

include/linux/sem.h

+3 −1
Original line number Diff line number Diff line
@@ -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 */