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kref: fix CPU ordering with respect to krefs

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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>
This commit is contained in:
Oliver Neukum 2007-04-02 14:47:59 +02:00 committed by Greg Kroah-Hartman
parent 74e9f5fa15
commit 1b0b3b9980
1 changed files with 2 additions and 0 deletions
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2
lib/kref.c
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@ -21,6 +21,7 @@
void kref_init(struct kref *kref) void kref_init(struct kref *kref)
{ {
atomic_set(&kref->refcount,1); atomic_set(&kref->refcount,1);
smp_mb();
} }
/** /**
@ -31,6 +32,7 @@ void kref_get(struct kref *kref)
{ {
WARN_ON(!atomic_read(&kref->refcount)); WARN_ON(!atomic_read(&kref->refcount));
atomic_inc(&kref->refcount); atomic_inc(&kref->refcount);
smp_mb__after_atomic_inc();
} }
/** /**