linux-kernel - [PATCH v2 1/2] watchdog: Introduce arch_watchdog_nmi_enable and arch_watchdog_nmi

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Date:   Thu, 13 Oct 2016 13:38:01 -0700
From:   Babu Moger <babu.moger@...cle.com>
To:     mingo@...nel.org, akpm@...ux-foundation.org, ak@...ux.intel.com,
        jkosina@...e.cz, baiyaowei@...s.chinamobile.com,
        dzickus@...hat.com, atomlin@...hat.com, uobergfe@...hat.com,
        tj@...nel.org, hidehiro.kawai.ez@...achi.com, johunt@...mai.com,
        davem@...emloft.net, sparclinux@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, sam@...nborg.org,
        babu.moger@...cle.com
Subject: [PATCH v2 1/2] watchdog: Introduce arch_watchdog_nmi_enable and arch_watchdog_nmi_disable

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 <babu.moger@...cle.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);
@@ -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();
+
+		return err;
+	}
+
+	return 0;
+}
+
 static int update_watchdog_all_cpus(void)
 {
 	int ret;
-- 
1.7.1