From: Oleg Nesterov <oleg@tv-sign.ru>

Make sure that spin_unlock_wait() is properly ordered wrt atomic_inc().

(akpm: can't we convert this code to use rwlocks?)

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 net/dccp/ccid.c |    1 +
 1 files changed, 1 insertion(+)

diff -puN net/dccp/ccid.c~fix-theoretical-ccids_readwrite_lock-race net/dccp/ccid.c
--- a/net/dccp/ccid.c~fix-theoretical-ccids_readwrite_lock-race
+++ a/net/dccp/ccid.c
@@ -40,6 +40,7 @@ static inline void ccids_write_unlock(vo
 static inline void ccids_read_lock(void)
 {
 	atomic_inc(&ccids_lockct);
+	smp_mb__after_atomic_inc();
 	spin_unlock_wait(&ccids_lock);
 }
 
_