srcu: No need to advance/accelerate if no callback enqueued

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>

kernel/rcu/srcutree.c

diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index ca8fcf5..ba9e695 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -1234,9 +1234,11 @@ static unsigned long srcu_gp_start_if_needed(struct srcu_struct *ssp,
 	if (rhp)
 		rcu_segcblist_enqueue(&sdp->srcu_cblist, rhp);
 	s = rcu_seq_snap(&ssp->srcu_sup->srcu_gp_seq);
-	rcu_segcblist_advance(&sdp->srcu_cblist,
-			      rcu_seq_current(&ssp->srcu_sup->srcu_gp_seq));
-	WARN_ON_ONCE(!rcu_segcblist_accelerate(&sdp->srcu_cblist, s) && rhp);
+	if (rhp) {
+		rcu_segcblist_advance(&sdp->srcu_cblist,
+				      rcu_seq_current(&ssp->srcu_sup->srcu_gp_seq));
+		WARN_ON_ONCE(!rcu_segcblist_accelerate(&sdp->srcu_cblist, s));
+	}
 	if (ULONG_CMP_LT(sdp->srcu_gp_seq_needed, s)) {
 		sdp->srcu_gp_seq_needed = s;
 		needgp = true;