| From | Greg Kroah-Hartman <> | Subject | [ 41/69] ipc/util.c, ipc_rcu_alloc: cacheline align allocation | Date | Wed, 16 Oct 2013 10:44:50 -0700 |
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3.10-stable review patch. If anyone has any objections, please let me know.
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From: Manfred Spraul <manfred@colorfullife.com>
commit 196aa0132fc7261f34b10ae1bfb44abc1bc69b3c upstream.
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.
[akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Manfred Spraul <manfred@colorfullife.com> Cc: Rik van Riel <riel@redhat.com> Cc: Davidlohr Bueso <davidlohr.bueso@hp.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- ipc/util.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)
--- 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 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;
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