sunrpc: Fix lockd sleeping until timeout

There is a race in enqueueing thread to a pool and
waking up a thread.
lockd doesn't wake up on reception of lock granted callback
if svc_wake_up() is called before lockd's thread is added
to a pool.

Signed-off-by: Andriy Skulysh <Andriy_Skulysh@xyratex.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index b8e47fac7315..5a9d40c5a9f3 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -499,7 +499,8 @@ void svc_wake_up(struct svc_serv *serv)
                         rqstp->rq_xprt = NULL;
                          */
                         wake_up(&rqstp->rq_wait);
-                }
+                } else
+                        pool->sp_task_pending = 1;
                 spin_unlock_bh(&pool->sp_lock);
         }
 }
@@ -634,7 +635,13 @@ struct svc_xprt *svc_get_next_xprt(struct svc_rqst *rqstp, long timeout)
                  * long for cache updates.
                  */
                 rqstp->rq_chandle.thread_wait = 1*HZ;
+                pool->sp_task_pending = 0;
         } else {
+                if (pool->sp_task_pending) {
+                        pool->sp_task_pending = 0;
+                        spin_unlock_bh(&pool->sp_lock);
+                        return ERR_PTR(-EAGAIN);
+                }
                 /* No data pending. Go to sleep */
                 svc_thread_enqueue(pool, rqstp);