[PATCH v3 1/2] watchdog: Introduce arch_watchdog_nmi_enable and arch_watchdog_nmi_disable

[Babu Moger]

Currently we do not have a way to enable/disable arch specific
watchdog handlers if it was implemented by any of the architectures.

This patch introduces new functions arch_watchdog_nmi_enable and
arch_watchdog_nmi_disable which can be used to enable/disable architecture
specific NMI watchdog handlers. These functions are defined as weak as
architectures can override their definitions to enable/disable nmi
watchdog behaviour.

Signed-off-by: Babu Moger 
---
 kernel/watchdog.c |   69 +++-
 1 files changed, 46 insertions(+), 23 deletions(-)

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 9acb29f..2d0765b 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -46,7 +46,7 @@
 
 static DEFINE_MUTEX(watchdog_proc_mutex);
 
-#ifdef CONFIG_HARDLOCKUP_DETECTOR
+#if defined(CONFIG_HARDLOCKUP_DETECTOR) || defined(CONFIG_HAVE_NMI_WATCHDOG)
 static unsigned long __read_mostly watchdog_enabled = 
SOFT_WATCHDOG_ENABLED|NMI_WATCHDOG_ENABLED;
 #else
 static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED;
@@ -585,15 +585,11 @@ static void watchdog(unsigned int cpu)
  */
 static unsigned long cpu0_err;
 
-static int watchdog_nmi_enable(unsigned int cpu)
+static int arch_watchdog_nmi_enable(unsigned int cpu)
 {
struct perf_event_attr *wd_attr;
struct perf_event *event = per_cpu(watchdog_ev, cpu);
 
-   /* nothing to do if the hard lockup detector is disabled */
-   if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
-   goto out;
-
/* is it already setup and enabled? */
if (event && event->state > PERF_EVENT_STATE_OFF)
goto out;
@@ -619,18 +615,6 @@ static int watchdog_nmi_enable(unsigned int cpu)
goto out_save;
}
 
-   /*
-* Disable the hard lockup detector if _any_ CPU fails to set up
-* set up the hardware perf event. The watchdog() function checks
-* the NMI_WATCHDOG_ENABLED bit periodically.
-*
-* The barriers are for syncing up watchdog_enabled across all the
-* cpus, as clear_bit() does not use barriers.
-*/
-   smp_mb__before_atomic();
-   clear_bit(NMI_WATCHDOG_ENABLED_BIT, _enabled);
-   smp_mb__after_atomic();
-
/* skip displaying the same error again */
if (cpu > 0 && (PTR_ERR(event) == cpu0_err))
return PTR_ERR(event);
@@ -645,8 +629,6 @@ static int watchdog_nmi_enable(unsigned int cpu)
pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
cpu, PTR_ERR(event));
 
-   pr_info("Shutting down hard lockup detector on all cpus\n");
-
return PTR_ERR(event);
 
/* success path */
@@ -658,7 +640,7 @@ out:
return 0;
 }
 
-static void watchdog_nmi_disable(unsigned int cpu)
+static void arch_watchdog_nmi_disable(unsigned int cpu)
 {
struct perf_event *event = per_cpu(watchdog_ev, cpu);
 
@@ -676,8 +658,13 @@ static void watchdog_nmi_disable(unsigned int cpu)
 }
 
 #else
-static int watchdog_nmi_enable(unsigned int cpu) { return 0; }
-static void watchdog_nmi_disable(unsigned int cpu) { return; }
+/*
+ * These two functions are mostly architecture specific
+ * defining them as weak here.
+ */
+int __weak arch_watchdog_nmi_enable(unsigned int cpu) { return 0; }
+void __weak arch_watchdog_nmi_disable(unsigned int cpu) { return; }
+
 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
 
 static struct smp_hotplug_thread watchdog_threads = {
@@ -781,6 +768,42 @@ void lockup_detector_resume(void)
put_online_cpus();
 }
 
+void watchdog_nmi_disable(unsigned int cpu)
+{
+   arch_watchdog_nmi_disable(cpu);
+}
+
+int watchdog_nmi_enable(unsigned int cpu)
+{
+   int err;
+
+   /* nothing to do if the hard lockup detector is disabled */
+   if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
+   return 0;
+
+   err = arch_watchdog_nmi_enable(cpu);
+
+   if (err) {
+   /*
+* Disable the hard lockup detector if _any_ CPU fails to set up
+* set up the hardware perf event. The watchdog() function 
checks
+* the NMI_WATCHDOG_ENABLED bit periodically.
+*
+* The barriers are for syncing up watchdog_enabled across all 
the
+* cpus, as clear_bit() does not use barriers.
+*/
+   smp_mb__before_atomic();
+   clear_bit(NMI_WATCHDOG_ENABLED_BIT, _enabled);
+   smp_mb__after_atomic();
+
+   pr_info("Shutting down hard lockup detector on all cpus\n");
+
+   return err;
+   }
+
+   return 0;
+}
+
 static int update_watchdog_all_cpus(void)
 {
int ret;
-- 
1.7.1

[PATCH v3 1/2] watchdog: Introduce arch_watchdog_nmi_enable and arch_watchdog_nmi_disable

[Babu Moger]

Currently we do not have a way to enable/disable arch specific
watchdog handlers if it was implemented by any of the architectures.

This patch introduces new functions arch_watchdog_nmi_enable and
arch_watchdog_nmi_disable which can be used to enable/disable architecture
specific NMI watchdog handlers. These functions are defined as weak as
architectures can override their definitions to enable/disable nmi
watchdog behaviour.

Signed-off-by: Babu Moger 
---
 kernel/watchdog.c |   69 +++-
 1 files changed, 46 insertions(+), 23 deletions(-)

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 9acb29f..2d0765b 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -46,7 +46,7 @@
 
 static DEFINE_MUTEX(watchdog_proc_mutex);
 
-#ifdef CONFIG_HARDLOCKUP_DETECTOR
+#if defined(CONFIG_HARDLOCKUP_DETECTOR) || defined(CONFIG_HAVE_NMI_WATCHDOG)
 static unsigned long __read_mostly watchdog_enabled = 
SOFT_WATCHDOG_ENABLED|NMI_WATCHDOG_ENABLED;
 #else
 static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED;
@@ -585,15 +585,11 @@ static void watchdog(unsigned int cpu)
  */
 static unsigned long cpu0_err;
 
-static int watchdog_nmi_enable(unsigned int cpu)
+static int arch_watchdog_nmi_enable(unsigned int cpu)
 {
struct perf_event_attr *wd_attr;
struct perf_event *event = per_cpu(watchdog_ev, cpu);
 
-   /* nothing to do if the hard lockup detector is disabled */
-   if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
-   goto out;
-
/* is it already setup and enabled? */
if (event && event->state > PERF_EVENT_STATE_OFF)
goto out;
@@ -619,18 +615,6 @@ static int watchdog_nmi_enable(unsigned int cpu)
goto out_save;
}
 
-   /*
-* Disable the hard lockup detector if _any_ CPU fails to set up
-* set up the hardware perf event. The watchdog() function checks
-* the NMI_WATCHDOG_ENABLED bit periodically.
-*
-* The barriers are for syncing up watchdog_enabled across all the
-* cpus, as clear_bit() does not use barriers.
-*/
-   smp_mb__before_atomic();
-   clear_bit(NMI_WATCHDOG_ENABLED_BIT, _enabled);
-   smp_mb__after_atomic();
-
/* skip displaying the same error again */
if (cpu > 0 && (PTR_ERR(event) == cpu0_err))
return PTR_ERR(event);
@@ -645,8 +629,6 @@ static int watchdog_nmi_enable(unsigned int cpu)
pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
cpu, PTR_ERR(event));
 
-   pr_info("Shutting down hard lockup detector on all cpus\n");
-
return PTR_ERR(event);
 
/* success path */
@@ -658,7 +640,7 @@ out:
return 0;
 }
 
-static void watchdog_nmi_disable(unsigned int cpu)
+static void arch_watchdog_nmi_disable(unsigned int cpu)
 {
struct perf_event *event = per_cpu(watchdog_ev, cpu);
 
@@ -676,8 +658,13 @@ static void watchdog_nmi_disable(unsigned int cpu)
 }
 
 #else
-static int watchdog_nmi_enable(unsigned int cpu) { return 0; }
-static void watchdog_nmi_disable(unsigned int cpu) { return; }
+/*
+ * These two functions are mostly architecture specific
+ * defining them as weak here.
+ */
+int __weak arch_watchdog_nmi_enable(unsigned int cpu) { return 0; }
+void __weak arch_watchdog_nmi_disable(unsigned int cpu) { return; }
+
 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
 
 static struct smp_hotplug_thread watchdog_threads = {
@@ -781,6 +768,42 @@ void lockup_detector_resume(void)
put_online_cpus();
 }
 
+void watchdog_nmi_disable(unsigned int cpu)
+{
+   arch_watchdog_nmi_disable(cpu);
+}
+
+int watchdog_nmi_enable(unsigned int cpu)
+{
+   int err;
+
+   /* nothing to do if the hard lockup detector is disabled */
+   if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
+   return 0;
+
+   err = arch_watchdog_nmi_enable(cpu);
+
+   if (err) {
+   /*
+* Disable the hard lockup detector if _any_ CPU fails to set up
+* set up the hardware perf event. The watchdog() function 
checks
+* the NMI_WATCHDOG_ENABLED bit periodically.
+*
+* The barriers are for syncing up watchdog_enabled across all 
the
+* cpus, as clear_bit() does not use barriers.
+*/
+   smp_mb__before_atomic();
+   clear_bit(NMI_WATCHDOG_ENABLED_BIT, _enabled);
+   smp_mb__after_atomic();
+
+   pr_info("Shutting down hard lockup detector on all cpus\n");
+
+   return err;
+   }
+
+   return 0;
+}
+
 static int update_watchdog_all_cpus(void)
 {
int ret;
-- 
1.7.1