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 <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Juergen Gross <[email protected]>
Cc: Valentin Schneider <[email protected]>
Cc: Yury Norov <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>

Author: imran-kn

kernel/smp.c

@@ -259,7 +259,8 @@ 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;