watchdog: Respect watchdog cpumask on CPU hotplug

The rework of the watchdog core to use cpu_stop_work broke the watchdog
cpumask on CPU hotplug.

The watchdog_enable/disable() functions are now called unconditionally from
the hotplug callback, i.e. even on CPUs which are not in the watchdog
cpumask. As a consequence the watchdog can become unstoppable.

Only invoke them when the plugged CPU is in the watchdog cpumask.

Fixes: 9cf57731b63e ("watchdog/softlockup: Replace "watchdog/%u" threads with cpu_stop_work")
Reported-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1903262245490.1789@nanos.tec.linutronix.de

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 403c9bd9041395a1d7919977acc7ed68d8c746ca..6a578723311328a6394941aeb9ff4eef6130b4ac 100644 (file)
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -554,13 +554,15 @@ static void softlockup_start_all(void)
 
 int lockup_detector_online_cpu(unsigned int cpu)
 {
-       watchdog_enable(cpu);
+       if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
+               watchdog_enable(cpu);
        return 0;
 }
 
 int lockup_detector_offline_cpu(unsigned int cpu)
 {
-       watchdog_disable(cpu);
+       if (cpumask_test_cpu(cpu, &watchdog_allowed_mask))
+               watchdog_disable(cpu);
        return 0;
 }