Commit-ID: 5ca0905f6787e930bc2a626cf1d8f69fab52acef
Gitweb: https://git.kernel.org/tip/5ca0905f6787e930bc2a626cf1d8f69fab52acef
Author: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
AuthorDate: Sun, 13 May 2018 20:15:41 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Thu, 12 Jul 2018 15:38:53 -0700
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) <joel@xxxxxxxxxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
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);
--
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