watchdog: introduce touch_softlockup_watchdog_sched()

touch_softlockup_watchdog() is used to tell watchdog that scheduler
stall is expected.  One group of usage is from paths where the task
may not be able to yield for a long time such as performing slow PIO
to finicky device and coming out of suspend.  The other is to account
for scheduler and timer going idle.

For scheduler softlockup detection, there's no reason to distinguish
the two cases; however, workqueue lockup detector is planned and it
can use the same signals from the former group while the latter would
spuriously prevent detection.  This patch introduces a new function
touch_softlockup_watchdog_sched() and convert the latter group to call
it instead.  For now, it just calls touch_softlockup_watchdog() and
there's no functional difference.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 14 insertions, 1 deletions

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 18f34cf75f74..9eaf3dbec7e8 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -225,7 +225,15 @@ static void __touch_watchdog(void)
 	__this_cpu_write(watchdog_touch_ts, get_timestamp());
 }
 
-void touch_softlockup_watchdog(void)
+/**
+ * touch_softlockup_watchdog_sched - touch watchdog on scheduler stalls
+ *
+ * Call when the scheduler may have stalled for legitimate reasons
+ * preventing the watchdog task from executing - e.g. the scheduler
+ * entering idle state.  This should only be used for scheduler events.
+ * Use touch_softlockup_watchdog() for everything else.
+ */
+void touch_softlockup_watchdog_sched(void)
 {
 	/*
 	 * Preemption can be enabled.  It doesn't matter which CPU's timestamp
@@ -233,6 +241,11 @@ void touch_softlockup_watchdog(void)
 	 */
 	raw_cpu_write(watchdog_touch_ts, 0);
 }
+
+void touch_softlockup_watchdog(void)
+{
+	touch_softlockup_watchdog_sched();
+}
 EXPORT_SYMBOL(touch_softlockup_watchdog);
 
 void touch_all_softlockup_watchdogs(void)