Branch HEAD

b=17461
i=r.read
i=tappro

avoid nesting of obd_uncommitted_replies and rs_lock locks
in ptlrpc_handle_rs.

diff --git a/lustre/ptlrpc/service.c b/lustre/ptlrpc/service.c
index 07e3c80..cb101cf 100644 (file)
--- a/lustre/ptlrpc/service.c
+++ b/lustre/ptlrpc/service.c
@@ -1598,19 +1598,19 @@ ptlrpc_handle_rs (struct ptlrpc_reply_state *rs)
         list_del_init (&rs->rs_exp_list);
         spin_unlock (&exp->exp_lock);
 
-        spin_lock(&rs->rs_lock);
-
-        been_handled = rs->rs_handled;
-        rs->rs_handled = 1;
-
-        if (!list_empty(&rs->rs_obd_list)) {
-                spin_unlock(&rs->rs_lock);
+        /* Avoid obd_uncommitted_replies_lock contention if we 100% sure that
+         * rs has been removed from the list already */
+        if (!list_empty_careful(&rs->rs_obd_list)) {
                 spin_lock(&obd->obd_uncommitted_replies_lock);
-                spin_lock(&rs->rs_lock);
                 list_del_init(&rs->rs_obd_list);
                 spin_unlock(&obd->obd_uncommitted_replies_lock);
         }
 
+        spin_lock(&rs->rs_lock);
+
+        been_handled = rs->rs_handled;
+        rs->rs_handled = 1;
+
         nlocks = rs->rs_nlocks;                 /* atomic "steal", but */
         rs->rs_nlocks = 0;                      /* locks still on rs_locks! */