From 5ca0905f6787e930bc2a626cf1d8f69fab52acef Mon Sep 17 00:00:00 2001 From: "Joel Fernandes (Google)" Date: Sun, 13 May 2018 20:15:41 -0700 Subject: [PATCH] rcu: Fix cpustart tracepoint gp_seq number The "cpustart" trace event shows a stale gp_seq. This is because it uses rdp->gp_seq, which is updated only at the end of the __note_gp_changes() function. This commit therefore instead uses rnp->gp_seq. An alternative fix would be to update rdp->gp_seq earlier, but this would break RCU's detection of the beginning of a new-to-this-CPU grace period. Signed-off-by: Joel Fernandes (Google) Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 73a33b82cfcd..973250503d98 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1801,7 +1801,7 @@ static bool __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp, * set up to detect a quiescent state, otherwise don't * go looking for one. */ - trace_rcu_grace_period(rsp->name, rdp->gp_seq, TPS("cpustart")); + trace_rcu_grace_period(rsp->name, rnp->gp_seq, TPS("cpustart")); need_gp = !!(rnp->qsmask & rdp->grpmask); rdp->cpu_no_qs.b.norm = need_gp; rdp->rcu_qs_ctr_snap = __this_cpu_read(rcu_dynticks.rcu_qs_ctr); -- 2.45.2