workqueue: wq_watchdog_touch is always called with valid CPU

BugLink: https://bugs.launchpad.net/bugs/2085849

[ Upstream commit 18e24deb1cc92f2068ce7434a94233741fbd7771 ]

Warn in the case it is called with cpu == -1. This does not appear
to happen anywhere.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Manuel Diewald <manuel.diewald@canonical.com>
Signed-off-by: Roxana Nicolescu <roxana.nicolescu@canonical.com>

kernel/workqueue.c

@@ -6534,6 +6534,8 @@ notrace void wq_watchdog_touch(int cpu)
 {
 	if (cpu >= 0)
 		per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
+	else
+		WARN_ONCE(1, "%s should be called with valid CPU", __func__);
 
 	wq_watchdog_touched = jiffies;
 }