From f45eede37a9011937e45dbae7ae1d588571a0fac Mon Sep 17 00:00:00 2001 From: Manfred Spraul Date: Fri, 28 Jun 2013 09:54:05 +1000 Subject: [PATCH] ipc/util.c, ipc_rcu_alloc: cacheline align allocation Enforce that ipc_rcu_alloc returns a cacheline aligned pointer on SMP. Rationale: The SysV sem code tries to move the main spinlock into a seperate cacheline (____cacheline_aligned_in_smp). This works only if ipc_rcu_alloc returns cacheline aligned pointers. vmalloc and kmalloc return cacheline algined pointers, the implementation of ipc_rcu_alloc breaks that. Signed-off-by: Manfred Spraul Cc: Rik van Riel Cc: Davidlohr Bueso Signed-off-by: Andrew Morton --- ipc/util.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/ipc/util.c b/ipc/util.c index a0c139f3d1f3..26d326899366 100644 --- a/ipc/util.c +++ b/ipc/util.c @@ -468,9 +468,7 @@ void ipc_free(void* ptr, int size) struct ipc_rcu { struct rcu_head rcu; atomic_t refcount; - /* "void *" makes sure alignment of following data is sane. */ - void *data[0]; -}; +} ____cacheline_aligned_in_smp; /** * ipc_rcu_alloc - allocate ipc and rcu space @@ -488,12 +486,14 @@ void *ipc_rcu_alloc(int size) if (unlikely(!out)) return NULL; atomic_set(&out->refcount, 1); - return out->data; + return out+1; } int ipc_rcu_getref(void *ptr) { - return atomic_inc_not_zero(&container_of(ptr, struct ipc_rcu, data)->refcount); + struct ipc_rcu *p = ((struct ipc_rcu*)ptr)-1; + + return atomic_inc_not_zero(&p->refcount); } /** @@ -507,7 +507,7 @@ static void ipc_schedule_free(struct rcu_head *head) void ipc_rcu_putref(void *ptr) { - struct ipc_rcu *p = container_of(ptr, struct ipc_rcu, data); + struct ipc_rcu *p = ((struct ipc_rcu*)ptr)-1; if (!atomic_dec_and_test(&p->refcount)) return; -- 2.39.5