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Message-Id: <20240802003426.4134196-6-paulmck@kernel.org>
Date: Thu, 1 Aug 2024 17:34:26 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: rcu@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
kernel-team@...a.com,
rostedt@...dmis.org,
"Paul E. McKenney" <paulmck@...nel.org>
Subject: [PATCH rcu 6/6] rcu/tasks: Add rcu_barrier_tasks*() start time to diagnostics
This commit adds the start time, in jiffies, of the most recently started
rcu_barrier_tasks*() operation to the diagnostic output used by rcuscale.
This information can be helpful in distinguishing a hung barrier operation
from a long series of barrier operations.
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
kernel/rcu/tasks.h | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 37597f7c581ca..2f8d6c8e3c4ce 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -85,6 +85,7 @@ struct rcu_tasks_percpu {
* @barrier_q_count: Number of queues being waited on.
* @barrier_q_completion: Barrier wait/wakeup mechanism.
* @barrier_q_seq: Sequence number for barrier operations.
+ * @barrier_q_start: Most recent barrier start in jiffies.
* @name: This flavor's textual name.
* @kname: This flavor's kthread name.
*/
@@ -120,6 +121,7 @@ struct rcu_tasks {
atomic_t barrier_q_count;
struct completion barrier_q_completion;
unsigned long barrier_q_seq;
+ unsigned long barrier_q_start;
char *name;
char *kname;
};
@@ -428,6 +430,7 @@ static void __maybe_unused rcu_barrier_tasks_generic(struct rcu_tasks *rtp)
mutex_unlock(&rtp->barrier_q_mutex);
return;
}
+ rtp->barrier_q_start = jiffies;
rcu_seq_start(&rtp->barrier_q_seq);
init_completion(&rtp->barrier_q_completion);
atomic_set(&rtp->barrier_q_count, 2);
@@ -783,8 +786,9 @@ static void rcu_tasks_torture_stats_print_generic(struct rcu_tasks *rtp, char *t
pr_cont(".\n");
else
pr_cont(" (none).\n");
- pr_alert("\tBarrier seq %lu count %d holdout CPUs ",
- data_race(rtp->barrier_q_seq), atomic_read(&rtp->barrier_q_count));
+ pr_alert("\tBarrier seq %lu start %lu count %d holdout CPUs ",
+ data_race(rtp->barrier_q_seq), j - data_race(rtp->barrier_q_start),
+ atomic_read(&rtp->barrier_q_count));
if (cpumask_available(cm) && !cpumask_empty(cm))
pr_cont(" %*pbl.\n", cpumask_pr_args(cm));
else
--
2.40.1
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