smp: Reduce logging due to dump_stack of CSD waiters

JIRA: https://issues.redhat.com/browse/RHEL-16867

commit 5bd00f6
Author: Imran Khan <imran.f.khan@oracle.com>
Date:   Tue, 9 May 2023 08:31:23 +1000

    smp: Reduce logging due to dump_stack of CSD waiters

    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@oracle.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Juergen Gross <jgross@suse.com>
    Cc: Valentin Schneider <vschneid@redhat.com>
    Cc: Yury Norov <yury.norov@gmail.com>
    Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Signed-off-by: Waiman Long <longman@redhat.com>

Author: Waiman-Long

kernel/smp.c

@@ -254,7 +254,8 @@ 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;