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percpu-refcount: Don't use silly cmpxchg() 

The cmpxchg() was just to ensure the debug check didn't race, which was
a bit excessive. The caller is supposed to do the appropriate
synchronization, which means percpu_ref_kill() can just do a simple
store.

Signed-off-by: Kent Overstreet <koverstreet@google.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Kent Overstreet 2013-06-03 16:02:29 -07:00 committed by Tejun Heo
parent 215e262f2a
commit c1ae6e9b4d
1 changed files with 4 additions and 15 deletions
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19
lib/percpu-refcount.c
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@ -107,22 +107,11 @@ static void percpu_ref_kill_rcu(struct rcu_head *rcu)
*/
void percpu_ref_kill(struct percpu_ref *ref)
{
unsigned __percpu *pcpu_count, *old, *new;
WARN_ONCE(REF_STATUS(ref->pcpu_count) == PCPU_REF_DEAD,
"percpu_ref_kill() called more than once!\n");
pcpu_count = ACCESS_ONCE(ref->pcpu_count);
do {
if (REF_STATUS(pcpu_count) == PCPU_REF_DEAD) {
WARN(1, "percpu_ref_kill() called more than once!\n");
return;
}
old = pcpu_count;
new = (unsigned __percpu *)
(((unsigned long) pcpu_count)|PCPU_REF_DEAD);
pcpu_count = cmpxchg(&ref->pcpu_count, old, new);
} while (pcpu_count != old);
ref->pcpu_count = (unsigned __percpu *)
(((unsigned long) ref->pcpu_count)|PCPU_REF_DEAD);
call_rcu(&ref->rcu, percpu_ref_kill_rcu);
}