rcu: Make expedited grace periods resolve stall-warning ties

Currently, if a grace period ends just as the stall-warning timeout
fires, an empty stall warning will be printed.  This is not helpful,
so this commit avoids these useless warnings by rechecking completion
after awakening in synchronize_sched_expedited_wait().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 33d7e255116507d7b7064d74ba4be0963d90bac8..bc6b79716a86c2c56fd78b994c534873572de528 100644 (file)
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3757,7 +3757,7 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
                                rsp->expedited_wq,
                                sync_rcu_preempt_exp_done(rnp_root),
                                jiffies_stall);
-               if (ret > 0)
+               if (ret > 0 || sync_rcu_preempt_exp_done(rnp_root))
                        return;
                if (ret < 0) {
                        /* Hit a signal, disable CPU stall warnings. */