From: "Paul E. McKenney" <paulmck@kernel.org>
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com,
mingo@kernel.org, jiangshanlai@gmail.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org,
"Jiangong.Han" <jiangong.han@windriver.com>,
"Paul E . McKenney" <paulmck@kernel.org>
Subject: [PATCH rcu 3/7] rcuscale: Console output claims too few grace periods
Date: Wed, 21 Jul 2021 14:04:37 -0700 [thread overview]
Message-ID: <20210721210441.796995-3-paulmck@kernel.org> (raw)
In-Reply-To: <20210721210421.GA788053@paulmck-ThinkPad-P17-Gen-1>
From: "Jiangong.Han" <jiangong.han@windriver.com>
The rcuscale console output claims N grace periods, numbered from zero
to N, which means that there were really N+1 grace periods. The root
cause of this bug is that rcu_scale_writer() stores the number of the
last grace period (numbered from zero) into writer_n_durations[me]
instead of the number of grace periods. This commit therefore assigns
the actual number of grace periods to writer_n_durations[me], and also
makes the corresponding adjustment to the loop outputting per-grace-period
measurements.
Sample of old console output:
rcu-scale: writer 0 gps: 133
......
rcu-scale: 0 writer-duration: 0 44003961
rcu-scale: 0 writer-duration: 1 32003582
......
rcu-scale: 0 writer-duration: 132 28004391
rcu-scale: 0 writer-duration: 133 27996410
Sample of new console output:
rcu-scale: writer 0 gps: 134
......
rcu-scale: 0 writer-duration: 0 44003961
rcu-scale: 0 writer-duration: 1 32003582
......
rcu-scale: 0 writer-duration: 132 28004391
rcu-scale: 0 writer-duration: 133 27996410
Signed-off-by: Jiangong.Han <jiangong.han@windriver.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/rcu/rcuscale.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c
index dca51fe9c73f2..2cc34a22a5060 100644
--- a/kernel/rcu/rcuscale.c
+++ b/kernel/rcu/rcuscale.c
@@ -487,7 +487,7 @@ rcu_scale_writer(void *arg)
if (gp_async) {
cur_ops->gp_barrier();
}
- writer_n_durations[me] = i_max;
+ writer_n_durations[me] = i_max + 1;
torture_kthread_stopping("rcu_scale_writer");
return 0;
}
@@ -561,7 +561,7 @@ rcu_scale_cleanup(void)
wdpp = writer_durations[i];
if (!wdpp)
continue;
- for (j = 0; j <= writer_n_durations[i]; j++) {
+ for (j = 0; j < writer_n_durations[i]; j++) {
wdp = &wdpp[j];
pr_alert("%s%s %4d writer-duration: %5d %llu\n",
scale_type, SCALE_FLAG,
--
2.31.1.189.g2e36527f23
next prev parent reply other threads:[~2021-07-21 21:04 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-21 21:04 [PATCH rcu 0/7] Torture-test updates for v5.15 Paul E. McKenney
2021-07-21 21:04 ` [PATCH rcu 1/7] refscale: Add measurement of clock readout Paul E. McKenney
2021-07-28 17:38 ` [PATCH v2 " Paul E. McKenney
2021-07-21 21:04 ` [PATCH rcu 2/7] rcutorture: Preempt rather than block when testing task stalls Paul E. McKenney
2021-07-21 21:04 ` Paul E. McKenney [this message]
2021-07-21 21:04 ` [PATCH rcu 4/7] locktorture: Mark statistics data races Paul E. McKenney
2021-07-21 21:04 ` [PATCH rcu 5/7] locktorture: Count lock readers Paul E. McKenney
2021-07-21 21:04 ` [PATCH rcu 6/7] scftorture: Add RPC-like IPI tests Paul E. McKenney
2021-07-21 21:04 ` [PATCH rcu 7/7] scftorture: Avoid NULL pointer exception on early exit Paul E. McKenney
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