[PATCH tick-sched] Clarify "NOHZ: local_softirq_pending" warning

From: Paul E. McKenney
Date: Fri Jun 26 2020 - 17:05:08 EST


Currently, can_stop_idle_tick() prints "NOHZ: local_softirq_pending HH"
(where "HH" is the hexadecimal softirq vector number) when one or more
non-RCU softirq handlers are still enablded when checking to stop the
scheduler-tick interrupt. This message is not as enlightening as one
might hope, so this commit changes it to "NOHZ tick-stop error: Non-RCU
local softirq work is pending, handler #HH.

Reported-by: Andy Lutomirski <luto@xxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>

---

tick-sched.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index f0199a4..349a25a 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -927,7 +927,7 @@ static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)

if (ratelimit < 10 &&
(local_softirq_pending() & SOFTIRQ_STOP_IDLE_MASK)) {
- pr_warn("NOHZ: local_softirq_pending %02x\n",
+ pr_warn("NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #%02x\n",
(unsigned int) local_softirq_pending());
ratelimit++;
}