watchdog: Disable watchdog when thresh is zero

This restores the previous behavior of softlock_thresh.

Currently, setting watchdog_thresh to zero causes the watchdog
kthreads to consume a lot of CPU.

In addition, the logic of proc_dowatchdog_thresh and
proc_dowatchdog_enabled has been factored into proc_dowatchdog.

Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
Cc: Marcin Slusarz <marcin.slusarz@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/1306127423-3347-3-git-send-email-msb@chromium.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
LKML-Reference: <20110517071018.GE22305@elte.hu>

4 files changed, 20 insertions, 23 deletions

diff --git a/include/linux/nmi.h b/include/linux/nmi.h
index c536f8545f7..5317b8b2198 100644
--- a/include/linux/nmi.h
+++ b/include/linux/nmi.h
@@ -47,9 +47,10 @@ static inline bool trigger_all_cpu_backtrace(void)
 int hw_nmi_is_cpu_stuck(struct pt_regs *);
 u64 hw_nmi_get_sample_period(void);
 extern int watchdog_enabled;
+extern int watchdog_thresh;
 struct ctl_table;
-extern int proc_dowatchdog_enabled(struct ctl_table *, int ,
-                        void __user *, size_t *, loff_t *);
+extern int proc_dowatchdog(struct ctl_table *, int ,
+                           void __user *, size_t *, loff_t *);
 #endif
 
 #endif
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 12211e1666e..d8b2d0bec0d 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -315,7 +315,6 @@ extern int proc_dowatchdog_thresh(struct ctl_table *table, int write,
                                   void __user *buffer,
                                   size_t *lenp, loff_t *ppos);
 extern unsigned int  softlockup_panic;
-extern int softlockup_thresh;
 void lockup_detector_init(void);
 #else
 static inline void touch_softlockup_watchdog(void)
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index c0bb32414b1..3dd0c46fa3b 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -730,14 +730,16 @@ static struct ctl_table kern_table[] = {
                 .data           = &watchdog_enabled,
                 .maxlen         = sizeof (int),
                 .mode           = 0644,
-                .proc_handler   = proc_dowatchdog_enabled,
+                .proc_handler   = proc_dowatchdog,
+                .extra1         = &zero,
+                .extra2         = &one,
         },
         {
                 .procname       = "watchdog_thresh",
-                .data           = &softlockup_thresh,
+                .data           = &watchdog_thresh,
                 .maxlen         = sizeof(int),
                 .mode           = 0644,
-                .proc_handler   = proc_dowatchdog_thresh,
+                .proc_handler   = proc_dowatchdog,
                 .extra1         = &neg_one,
                 .extra2         = &sixty,
         },
@@ -755,7 +757,9 @@ static struct ctl_table kern_table[] = {
                 .data           = &watchdog_enabled,
                 .maxlen         = sizeof (int),
                 .mode           = 0644,
-                .proc_handler   = proc_dowatchdog_enabled,
+                .proc_handler   = proc_dowatchdog,
+                .extra1         = &zero,
+                .extra2         = &one,
         },
 #endif
 #if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86)
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index cf0e09f452e..60301916f62 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -28,7 +28,7 @@
 #include <linux/perf_event.h>
 
 int watchdog_enabled = 1;
-int __read_mostly softlockup_thresh = 60;
+int __read_mostly watchdog_thresh = 60;
 
 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
 static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
@@ -105,12 +105,12 @@ static unsigned long get_timestamp(int this_cpu)
 static unsigned long get_sample_period(void)
 {
         /*
-         * convert softlockup_thresh from seconds to ns
+         * convert watchdog_thresh from seconds to ns
          * the divide by 5 is to give hrtimer 5 chances to
          * increment before the hardlockup detector generates
          * a warning
          */
-        return softlockup_thresh * (NSEC_PER_SEC / 5);
+        return watchdog_thresh * (NSEC_PER_SEC / 5);
 }
 
 /* Commands for resetting the watchdog */
@@ -182,7 +182,7 @@ static int is_softlockup(unsigned long touch_ts)
         unsigned long now = get_timestamp(smp_processor_id());
 
         /* Warn about unreasonable delays: */
-        if (time_after(now, touch_ts + softlockup_thresh))
+        if (time_after(now, touch_ts + watchdog_thresh))
                 return now - touch_ts;
 
         return 0;
@@ -501,19 +501,19 @@ static void watchdog_disable_all_cpus(void)
 /* sysctl functions */
 #ifdef CONFIG_SYSCTL
 /*
- * proc handler for /proc/sys/kernel/nmi_watchdog
+ * proc handler for /proc/sys/kernel/nmi_watchdog,watchdog_thresh
  */
 
-int proc_dowatchdog_enabled(struct ctl_table *table, int write,
-                     void __user *buffer, size_t *length, loff_t *ppos)
+int proc_dowatchdog(struct ctl_table *table, int write,
+                    void __user *buffer, size_t *lenp, loff_t *ppos)
 {
         int ret;
 
-        ret = proc_dointvec(table, write, buffer, length, ppos);
+        ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
         if (ret || !write)
                 goto out;
 
-        if (watchdog_enabled)
+        if (watchdog_enabled && watchdog_thresh)
                 watchdog_enable_all_cpus();
         else
                 watchdog_disable_all_cpus();
@@ -521,13 +521,6 @@ int proc_dowatchdog_enabled(struct ctl_table *table, int write,
 out:
         return ret;
 }
-
-int proc_dowatchdog_thresh(struct ctl_table *table, int write,
-                             void __user *buffer,
-                             size_t *lenp, loff_t *ppos)
-{
-        return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
-}
 #endif /* CONFIG_SYSCTL */