powerpc/watchdog: add locking around init/exit functions

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>

diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c
index 12e90ae712fed34ba500a0c1c9f32a1c14c27fdb..34721a257a770c450baac0288f8006c94ff1975b 100644 (file)
--- a/arch/powerpc/kernel/watchdog.c
+++ b/arch/powerpc/kernel/watchdog.c
@@ -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;