linux-kernel - [PATCH csd-lock 1/2] smp: Reduce logging due to dump

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Message-Id: <20230612205036.292542-1-paulmck@kernel.org>
Date:   Mon, 12 Jun 2023 13:50:35 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     peterz@...radead.org, jgross@...e.com, vschneid@...hat.com,
        yury.norov@...il.com
Cc:     linux-kernel@...r.kernel.org, imran.f.khan@...cle.com,
        kernel-team@...a.com, "Paul E . McKenney" <paulmck@...nel.org>
Subject: [PATCH csd-lock 1/2] smp: Reduce logging due to dump_stack of CSD waiters

From: Imran Khan <imran.f.khan@...cle.com>

If a waiter is waiting for CSD lock, its call stack will not change
between first and subsequent hang detection for the same CSD lock.
Therefore, do dump_stack only for first-time detection for a given waiter.

This avoids excessive logging on systems with hundreds of CPUs where
repetitive dump_stack from hundreds of CPUs would otherwise flood the
console.

Signed-off-by: Imran Khan <imran.f.khan@...cle.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Juergen Gross <jgross@...e.com>
Cc: Valentin Schneider <vschneid@...hat.com>
Cc: Yury Norov <yury.norov@...il.com>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 kernel/smp.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/smp.c b/kernel/smp.c
index ab3e5dad6cfe..b7ccba677a0a 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -248,7 +248,8 @@ static bool csd_lock_wait_toolong(struct __call_single_data *csd, u64 ts0, u64 *
 			arch_send_call_function_single_ipi(cpu);
 		}
 	}
-	dump_stack();
+	if (firsttime)
+		dump_stack();
 	*ts1 = ts2;
 
 	return false;
-- 
2.40.1