[PATCH 2/2] powerpc/watchdog: ensure watchdog data accesses are protected

[Laurent Dufour]

The wd_smp_cpus_pending CPU mask should be accessed under the protection of
the __wd_smp_lock.

This prevents false alarm to be raised when the system is under an heavy
stress. This has been seen while doing LPM on large system with a big
workload.

Signed-off-by: Laurent Dufour <lduf...@linux.ibm.com>
---
 arch/powerpc/kernel/watchdog.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c
index bc7411327066..8d7a1a86187e 100644
--- a/arch/powerpc/kernel/watchdog.c
+++ b/arch/powerpc/kernel/watchdog.c
@@ -203,12 +203,13 @@ static void watchdog_smp_panic(int cpu, u64 tb)
 
 static void wd_smp_clear_cpu_pending(int cpu, u64 tb)
 {
+       unsigned long flags;
+
+       wd_smp_lock(&flags);
        if (!cpumask_test_cpu(cpu, &wd_smp_cpus_pending)) {
                if (unlikely(cpumask_test_cpu(cpu, &wd_smp_cpus_stuck))) {
                        struct pt_regs *regs = get_irq_regs();
-                       unsigned long flags;
 
-                       wd_smp_lock(&flags);
                        cpumask_clear_cpu(cpu, &wd_smp_cpus_stuck);
                        wd_smp_unlock(&flags);
 
@@ -219,22 +220,23 @@ static void wd_smp_clear_cpu_pending(int cpu, u64 tb)
                                show_regs(regs);
                        else
                                dump_stack();
+                       return;
                }
+
+               wd_smp_unlock(&flags);
                return;
        }
+
        cpumask_clear_cpu(cpu, &wd_smp_cpus_pending);
        if (cpumask_empty(&wd_smp_cpus_pending)) {
-               unsigned long flags;
-
-               wd_smp_lock(&flags);
                if (cpumask_empty(&wd_smp_cpus_pending)) {
                        wd_smp_last_reset_tb = tb;
                        cpumask_andnot(&wd_smp_cpus_pending,
                                        &wd_cpus_enabled,
                                        &wd_smp_cpus_stuck);
                }
-               wd_smp_unlock(&flags);
        }
+       wd_smp_unlock(&flags);
 }
 
 static void watchdog_timer_interrupt(int cpu)
-- 
2.33.1