linux-kernel - [PATCH 1/2] watchdog: rename watchdog_suspend() and watchdog

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Date:	Fri,  7 Aug 2015 11:58:07 +0200
From:	Ulrich Obergfell <uobergfe@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	akpm@...ux-foundation.org, dzickus@...hat.com, atomlin@...hat.com,
	uobergfe@...hat.com, jolsa@...nel.org, mhocko@...e.cz,
	eranian@...gle.com, cmetcalf@...hip.com, fweisbec@...il.com,
	linux@...ck-us.net
Subject: [PATCH 1/2] watchdog: rename watchdog_suspend() and watchdog_resume()

Rename watchdog_suspend() to lockup_detector_suspend() and
watchdog_resume() to lockup_detector_resume() to avoid
confusion with the watchdog subsystem and to be consistent
with the existing name lockup_detector_init().

Also provide comment blocks to explain the watchdog_running
and watchdog_suspended variables and their relationship.

Signed-off-by: Ulrich Obergfell <uobergfe@...hat.com>
---
 arch/x86/kernel/cpu/perf_event_intel.c |  4 ++--
 include/linux/nmi.h                    |  8 ++++----
 kernel/watchdog.c                      | 26 ++++++++++++++++++++++----
 3 files changed, 28 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index d4e1b0c..0357bf7 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -3368,7 +3368,7 @@ static __init int fixup_ht_bug(void)
 		return 0;
 	}
 
-	if (watchdog_suspend() != 0) {
+	if (lockup_detector_suspend() != 0) {
 		pr_info("failed to disable PMU erratum BJ122, BV98, HSD29 workaround\n");
 		return 0;
 	}
@@ -3379,7 +3379,7 @@ static __init int fixup_ht_bug(void)
 	x86_pmu.commit_scheduling = NULL;
 	x86_pmu.stop_scheduling = NULL;
 
-	watchdog_resume();
+	lockup_detector_resume();
 
 	get_online_cpus();
 
diff --git a/include/linux/nmi.h b/include/linux/nmi.h
index 46e28e9e..78488e0 100644
--- a/include/linux/nmi.h
+++ b/include/linux/nmi.h
@@ -84,15 +84,15 @@ extern int proc_watchdog_thresh(struct ctl_table *, int ,
 				void __user *, size_t *, loff_t *);
 extern int proc_watchdog_cpumask(struct ctl_table *, int,
 				 void __user *, size_t *, loff_t *);
-extern int watchdog_suspend(void);
-extern void watchdog_resume(void);
+extern int lockup_detector_suspend(void);
+extern void lockup_detector_resume(void);
 #else
-static inline int watchdog_suspend(void)
+static inline int lockup_detector_suspend(void)
 {
 	return 0;
 }
 
-static inline void watchdog_resume(void)
+static inline void lockup_detector_resume(void)
 {
 }
 #endif
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 69666f4..64ed1c3 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -67,8 +67,26 @@ unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
 #define for_each_watchdog_cpu(cpu) \
 	for_each_cpu_and((cpu), cpu_online_mask, &watchdog_cpumask)
 
-static int __read_mostly watchdog_suspended;
+/*
+ * The 'watchdog_running' variable is set to 1 when the watchdog threads
+ * are registered/started and is set to 0 when the watchdog threads are
+ * unregistered/stopped, so it is an indicator whether the threads exist.
+ */
 static int __read_mostly watchdog_running;
+/*
+ * If a subsystem has a need to deactivate the watchdog temporarily, it
+ * can use the suspend/resume interface to achieve this. The content of
+ * the 'watchdog_suspended' variable reflects this state. Existing threads
+ * are parked/unparked by the lockup_detector_{suspend|resume} functions
+ * (see comment blocks pertaining to those functions for further details).
+ *
+ * 'watchdog_suspended' also prevents threads from being registered/started
+ * or unregistered/stopped via parameters in /proc/sys/kernel, so the state
+ * of 'watchdog_running' cannot change while the watchdog is deactivated
+ * temporarily (see related code in 'proc' handlers).
+ */
+static int __read_mostly watchdog_suspended;
+
 static u64 __read_mostly sample_period;
 
 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
@@ -669,7 +687,7 @@ static void watchdog_unpark_threads(void)
 /*
  * Suspend the hard and soft lockup detector by parking the watchdog threads.
  */
-int watchdog_suspend(void)
+int lockup_detector_suspend(void)
 {
 	int ret = 0;
 
@@ -679,7 +697,7 @@ int watchdog_suspend(void)
 	 * the 'watchdog_suspended' variable). If the watchdog threads are
 	 * running, the first caller takes care that they will be parked.
 	 * The state of 'watchdog_running' cannot change while a suspend
-	 * request is active (see related changes in 'proc' handlers).
+	 * request is active (see related code in 'proc' handlers).
 	 */
 	if (watchdog_running && !watchdog_suspended)
 		ret = watchdog_park_threads();
@@ -695,7 +713,7 @@ int watchdog_suspend(void)
 /*
  * Resume the hard and soft lockup detector by unparking the watchdog threads.
  */
-void watchdog_resume(void)
+void lockup_detector_resume(void)
 {
 	mutex_lock(&watchdog_proc_mutex);
 
-- 
1.7.11.7

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