Messages in this thread Patch in this message | | | From | "Paul E. McKenney" <> | Subject | [PATCH tip/core/rcu 34/40] rcu: Fix cpustart tracepoint gp_seq number | Date | Mon, 25 Jun 2018 17:08:53 -0700 |
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From: "Joel Fernandes (Google)" <joel@joelfernandes.org>
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@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> --- 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 8dab564be8e7..5c6f59b4fc9c 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); -- 2.17.1
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