SUNRPC: Fix potential races in xprt_lock_write_next()

We have to ensure that the wake up from the waitqueue and the assignment
of xprt->snd_task are atomic. We can do this by assigning the snd_task
while under the waitqueue spinlock.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 8 insertions, 5 deletions

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 360240cc1e9b..828a76590af9 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -385,17 +385,20 @@ nfs4_free_slot(struct nfs4_slot_table *tbl, u8 free_slotid)
                 free_slotid, tbl->highest_used_slotid);
 }
 
+bool nfs4_set_task_privileged(struct rpc_task *task, void *dummy)
+{
+        rpc_task_set_priority(task, RPC_PRIORITY_PRIVILEGED);
+        return true;
+}
+
 /*
  * Signal state manager thread if session fore channel is drained
  */
 static void nfs4_check_drain_fc_complete(struct nfs4_session *ses)
 {
-        struct rpc_task *task;
-
         if (!test_bit(NFS4_SESSION_DRAINING, &ses->session_state)) {
-                task = rpc_wake_up_next(&ses->fc_slot_table.slot_tbl_waitq);
-                if (task)
-                        rpc_task_set_priority(task, RPC_PRIORITY_PRIVILEGED);
+                rpc_wake_up_first(&ses->fc_slot_table.slot_tbl_waitq,
+                                nfs4_set_task_privileged, NULL);
                 return;
         }