powerpc/watchdog: add locking around init/exit functions
authorNicholas Piggin <npiggin@gmail.com>
Wed, 9 Aug 2017 12:41:26 +0000 (22:41 +1000)
committerMichael Ellerman <mpe@ellerman.id.au>
Wed, 9 Aug 2017 13:45:33 +0000 (23:45 +1000)
When CPUs start and stop the watchdog, they manipulate shared data
that is normally protected by the lock. Other CPUs can be running
concurrently at this time, so it's a good idea to use locking here
to be on the safe side.

Remove the barrier which is undocumented and didn't do anything.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
arch/powerpc/kernel/watchdog.c

index 12e90ae712fed34ba500a0c1c9f32a1c14c27fdb..34721a257a770c450baac0288f8006c94ff1975b 100644 (file)
@@ -297,6 +297,8 @@ static void stop_watchdog_timer_on(unsigned int cpu)
 
 static int start_wd_on_cpu(unsigned int cpu)
 {
+       unsigned long flags;
+
        if (cpumask_test_cpu(cpu, &wd_cpus_enabled)) {
                WARN_ON(1);
                return 0;
@@ -311,12 +313,14 @@ static int start_wd_on_cpu(unsigned int cpu)
        if (!cpumask_test_cpu(cpu, &watchdog_cpumask))
                return 0;
 
+       wd_smp_lock(&flags);
        cpumask_set_cpu(cpu, &wd_cpus_enabled);
        if (cpumask_weight(&wd_cpus_enabled) == 1) {
                cpumask_set_cpu(cpu, &wd_smp_cpus_pending);
                wd_smp_last_reset_tb = get_tb();
        }
-       smp_wmb();
+       wd_smp_unlock(&flags);
+
        start_watchdog_timer_on(cpu);
 
        return 0;
@@ -324,12 +328,17 @@ static int start_wd_on_cpu(unsigned int cpu)
 
 static int stop_wd_on_cpu(unsigned int cpu)
 {
+       unsigned long flags;
+
        if (!cpumask_test_cpu(cpu, &wd_cpus_enabled))
                return 0; /* Can happen in CPU unplug case */
 
        stop_watchdog_timer_on(cpu);
 
+       wd_smp_lock(&flags);
        cpumask_clear_cpu(cpu, &wd_cpus_enabled);
+       wd_smp_unlock(&flags);
+
        wd_smp_clear_cpu_pending(cpu, get_tb());
 
        return 0;