[RFC PATCH 1/2] smp: Reduce logging due to dump_stack of CSD waiters.

[Imran Khan <imran.f.khan@oracle.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.
So dump_stack for the waiter only for first time detection.

This avoids excessive logging on large scale systems(with hundreds
of CPUs) where repetitive dump_stack from hundreds of CPUs can flood
the console.

Signed-off-by: Imran Khan <imran.f.khan@oracle.com>
---
 kernel/smp.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/smp.c b/kernel/smp.c
index ab3e5dad6cfe9..b7ccba677a0a0 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;
-- 
2.34.1