Use bit_lock operation to prevent multiple soft-lockups reports when
one CPU already triggered dumping backtraces from all CPUs.
It allows to remove the explicit memory barriers and misleading
comments.
Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Petr Mladek <pmladek@xxxxxxxx>
---
Andrew,
this patch can be put on top of the patchset fixing/cleaning softlockup
watchdog code. Feel free to squash it into the other patch fixing
the barriers.
Or should I resend the entire patchset again, please?
Best Regards,
Petr
kernel/watchdog.c | 15 ++-------------
1 file changed, 2 insertions(+), 13 deletions(-)
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index c050323fcd33..090b6bc4de79 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -410,13 +410,8 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
* engaged in dumping all cpu back traces.
*/
if (softlockup_all_cpu_backtrace) {
- if (test_and_set_bit(0, &soft_lockup_nmi_warn))
+ if (test_and_set_bit_lock(0, &soft_lockup_nmi_warn))
return HRTIMER_RESTART;
- /*
- * Make sure that reports are serialized. Start
- * printing after getting the exclusive rights.
- */
- smp_mb__after_atomic();
}
/* Start period for the next softlockup warning. */
@@ -434,13 +429,7 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
if (softlockup_all_cpu_backtrace) {
trigger_allbutself_cpu_backtrace();
- /*
- * Make sure that everything is printed before
- * another CPU is allowed to report lockup again.
- */
- smp_mb__before_atomic();
- /* Allow a further report. */
- clear_bit(0, &soft_lockup_nmi_warn);
+ clear_bit_unlock(0, &soft_lockup_nmi_warn);
}
add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
--
2.26.2
