Don,

On 10/17/2016 12:31 PM, Don Zickus wrote:
On Thu, Oct 13, 2016 at 01:38:01PM -0700, Babu Moger wrote:
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.
Hi Babu,

This patch tested fine on my x86 box and I am ok with the changes.

I do have one small cosmetic request below for a failure path.  Other than
that I will give my ack.
Yes. I am testing these changes. If everything goes as expected, I will post v3 version
tomorrow. Thanks Babu


Cheers,
Don

Signed-off-by: Babu Moger <babu.mo...@oracle.com>
---
  kernel/watchdog.c |   65 +++++++++++++++++++++++++++++++++++-----------------
  1 files changed, 44 insertions(+), 21 deletions(-)

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 9acb29f..d1e84e6 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, &watchdog_enabled);
-       smp_mb__after_atomic();
-
        /* skip displaying the same error again */
        if (cpu > 0 && (PTR_ERR(event) == cpu0_err))
                return PTR_ERR(event);
In the arch_watchdog_nmi_enable code is a pr_info on failure

        pr_info("Shutting down hard lockup detector on all cpus\n");

that should be moved to below..


@@ -658,7 +642,7 @@ 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 +660,13 @@ 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 +770,40 @@ 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, &watchdog_enabled);
+               smp_mb__after_atomic();
moved to here:

                pr_info("Shutting down hard lockup detector on all cpus\n");


This lets the failure message be displayed on all arches instead of just
x86.  Though I guess sparc does not call theirs 'hard lockup detector'.
Hmm...


+
+               return err;
+       }
+
+       return 0;
+}
+
  static int update_watchdog_all_cpus(void)
  {
        int ret;
--
1.7.1


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