[PATCH 12/46] kref: fix CPU ordering with respect to krefs

Greg Kroah-Hartman
2007-04-27T19:15:54Z

From: Oliver Neukum <oneukum@suse.de>

some atomic operations are only atomic, not ordered. Thus a CPU is allowed
to reorder memory references to an object to before the reference is
obtained. This fixes it.

Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
lib/kref.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/lib/kref.c b/lib/kref.c
index 0d07cc3..a6dc3ec 100644
--- a/lib/kref.c
+++ b/lib/kref.c
@@ -21,6 +21,7 @@
void kref_init(struct kref *kref)
{
atomic_set(&kref->refcount,1);
+ smp_mb();
}

/**
@@ -31,6 +32,7 @@ void kref_get(struct kref *kref)
{
WARN_ON(!atomic_read(&kref->refcount));
atomic_inc(&kref->refcount);
+ smp_mb__after_atomic_inc();
}

/**
--
1.5.1.2