Commit 196aa013 authored by Manfred Spraul's avatar Manfred Spraul Committed by Linus Torvalds

ipc/util.c, ipc_rcu_alloc: cacheline align allocation

Enforce that ipc_rcu_alloc returns a cacheline aligned pointer on SMP.


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.

[ coding-style fixes]
Signed-off-by: default avatarManfred Spraul <>
Cc: Rik van Riel <>
Cc: Davidlohr Bueso <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 9ad66ae6
......@@ -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))
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