watchdog: Use hotplug thread infrastructure

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/20120716103948.563736676@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 89 insertions, 174 deletions

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 4b1dfba70f7c..9d4c8d5a1f53 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -22,6 +22,7 @@
 #include <linux/notifier.h>
 #include <linux/module.h>
 #include <linux/sysctl.h>
+#include <linux/smpboot.h>
 
 #include <asm/irq_regs.h>
 #include <linux/kvm_para.h>
@@ -29,16 +30,18 @@
 
 int watchdog_enabled = 1;
 int __read_mostly watchdog_thresh = 10;
+static int __read_mostly watchdog_disabled;
 
 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
 static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
 static DEFINE_PER_CPU(bool, soft_watchdog_warn);
+static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
+static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt);
 #ifdef CONFIG_HARDLOCKUP_DETECTOR
 static DEFINE_PER_CPU(bool, hard_watchdog_warn);
 static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
-static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved);
 static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
 #endif
@@ -248,13 +251,15 @@ static void watchdog_overflow_callback(struct perf_event *event,
         __this_cpu_write(hard_watchdog_warn, false);
         return;
 }
+#endif /* CONFIG_HARDLOCKUP_DETECTOR */
+
 static void watchdog_interrupt_count(void)
 {
         __this_cpu_inc(hrtimer_interrupts);
 }
-#else
-static inline void watchdog_interrupt_count(void) { return; }
-#endif /* CONFIG_HARDLOCKUP_DETECTOR */
+
+static int watchdog_nmi_enable(unsigned int cpu);
+static void watchdog_nmi_disable(unsigned int cpu);
 
 /* watchdog kicker functions */
 static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
@@ -327,49 +332,68 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
         return HRTIMER_RESTART;
 }
 
+static void watchdog_set_prio(unsigned int policy, unsigned int prio)
+{
+        struct sched_param param = { .sched_priority = prio };
 
-/*
- * The watchdog thread - touches the timestamp.
- */
-static int watchdog(void *unused)
+        sched_setscheduler(current, policy, &param);
+}
+
+static void watchdog_enable(unsigned int cpu)
 {
-        struct sched_param param = { .sched_priority = 0 };
         struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
 
-        /* initialize timestamp */
-        __touch_watchdog();
+        if (!watchdog_enabled) {
+                kthread_park(current);
+                return;
+        }
+
+        /* Enable the perf event */
+        watchdog_nmi_enable(cpu);
 
         /* kick off the timer for the hardlockup detector */
+        hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+        hrtimer->function = watchdog_timer_fn;
+
         /* done here because hrtimer_start can only pin to smp_processor_id() */
         hrtimer_start(hrtimer, ns_to_ktime(get_sample_period()),
                       HRTIMER_MODE_REL_PINNED);
 
-        set_current_state(TASK_INTERRUPTIBLE);
-        /*
-         * Run briefly (kicked by the hrtimer callback function) once every
-         * get_sample_period() seconds (4 seconds by default) to reset the
-         * softlockup timestamp. If this gets delayed for more than
-         * 2*watchdog_thresh seconds then the debug-printout triggers in
-         * watchdog_timer_fn().
-         */
-        while (!kthread_should_stop()) {
-                __touch_watchdog();
-                schedule();
+        /* initialize timestamp */
+        watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1);
+        __touch_watchdog();
+}
 
-                if (kthread_should_stop())
-                        break;
+static void watchdog_disable(unsigned int cpu)
+{
+        struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
 
-                set_current_state(TASK_INTERRUPTIBLE);
-        }
-        /*
-         * Drop the policy/priority elevation during thread exit to avoid a
-         * scheduling latency spike.
-         */
-        __set_current_state(TASK_RUNNING);
-        sched_setscheduler(current, SCHED_NORMAL, &param);
-        return 0;
+        watchdog_set_prio(SCHED_NORMAL, 0);
+        hrtimer_cancel(hrtimer);
+        /* disable the perf event */
+        watchdog_nmi_disable(cpu);
 }
 
+static int watchdog_should_run(unsigned int cpu)
+{
+        return __this_cpu_read(hrtimer_interrupts) !=
+                __this_cpu_read(soft_lockup_hrtimer_cnt);
+}
+
+/*
+ * The watchdog thread function - touches the timestamp.
+ *
+ * It only runs once every get_sample_period() seconds (4 seconds by
+ * default) to reset the softlockup timestamp. If this gets delayed
+ * for more than 2*watchdog_thresh seconds then the debug-printout
+ * triggers in watchdog_timer_fn().
+ */
+static void watchdog(unsigned int cpu)
+{
+        __this_cpu_write(soft_lockup_hrtimer_cnt,
+                         __this_cpu_read(hrtimer_interrupts));
+        __touch_watchdog();
+}
 
 #ifdef CONFIG_HARDLOCKUP_DETECTOR
 /*
@@ -379,7 +403,7 @@ static int watchdog(void *unused)
  */
 static unsigned long cpu0_err;
 
-static int watchdog_nmi_enable(int cpu)
+static int watchdog_nmi_enable(unsigned int cpu)
 {
         struct perf_event_attr *wd_attr;
         struct perf_event *event = per_cpu(watchdog_ev, cpu);
@@ -433,7 +457,7 @@ out:
         return 0;
 }
 
-static void watchdog_nmi_disable(int cpu)
+static void watchdog_nmi_disable(unsigned int cpu)
 {
         struct perf_event *event = per_cpu(watchdog_ev, cpu);
 
@@ -447,107 +471,35 @@ static void watchdog_nmi_disable(int cpu)
         return;
 }
 #else
-static int watchdog_nmi_enable(int cpu) { return 0; }
-static void watchdog_nmi_disable(int cpu) { return; }
+static int watchdog_nmi_enable(unsigned int cpu) { return 0; }
+static void watchdog_nmi_disable(unsigned int cpu) { return; }
 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
 
 /* prepare/enable/disable routines */
-static void watchdog_prepare_cpu(int cpu)
-{
-        struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
-
-        WARN_ON(per_cpu(softlockup_watchdog, cpu));
-        hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
-        hrtimer->function = watchdog_timer_fn;
-}
-
-static int watchdog_enable(int cpu)
-{
-        struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
-        int err = 0;
-
-        /* enable the perf event */
-        err = watchdog_nmi_enable(cpu);
-
-        /* Regardless of err above, fall through and start softlockup */
-
-        /* create the watchdog thread */
-        if (!p) {
-                struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
-                p = kthread_create_on_node(watchdog, NULL, cpu_to_node(cpu), "watchdog/%d", cpu);
-                if (IS_ERR(p)) {
-                        pr_err("softlockup watchdog for %i failed\n", cpu);
-                        if (!err) {
-                                /* if hardlockup hasn't already set this */
-                                err = PTR_ERR(p);
-                                /* and disable the perf event */
-                                watchdog_nmi_disable(cpu);
-                        }
-                        goto out;
-                }
-                sched_setscheduler(p, SCHED_FIFO, &param);
-                kthread_bind(p, cpu);
-                per_cpu(watchdog_touch_ts, cpu) = 0;
-                per_cpu(softlockup_watchdog, cpu) = p;
-                wake_up_process(p);
-        }
-
-out:
-        return err;
-}
-
-static void watchdog_disable(int cpu)
-{
-        struct task_struct *p = per_cpu(softlockup_watchdog, cpu);
-        struct hrtimer *hrtimer = &per_cpu(watchdog_hrtimer, cpu);
-
-        /*
-         * cancel the timer first to stop incrementing the stats
-         * and waking up the kthread
-         */
-        hrtimer_cancel(hrtimer);
-
-        /* disable the perf event */
-        watchdog_nmi_disable(cpu);
-
-        /* stop the watchdog thread */
-        if (p) {
-                per_cpu(softlockup_watchdog, cpu) = NULL;
-                kthread_stop(p);
-        }
-}
-
 /* sysctl functions */
 #ifdef CONFIG_SYSCTL
 static void watchdog_enable_all_cpus(void)
 {
-        int cpu;
-
-        watchdog_enabled = 0;
-
-        for_each_online_cpu(cpu)
-                if (!watchdog_enable(cpu))
-                        /* if any cpu succeeds, watchdog is considered
-                           enabled for the system */
-                        watchdog_enabled = 1;
-
-        if (!watchdog_enabled)
-                pr_err("failed to be enabled on some cpus\n");
+        unsigned int cpu;
 
+        if (watchdog_disabled) {
+                watchdog_disabled = 0;
+                for_each_online_cpu(cpu)
+                        kthread_unpark(per_cpu(softlockup_watchdog, cpu));
+        }
 }
 
 static void watchdog_disable_all_cpus(void)
 {
-        int cpu;
-
-        for_each_online_cpu(cpu)
-                watchdog_disable(cpu);
+        unsigned int cpu;
 
-        /* if all watchdogs are disabled, then they are disabled for the system */
-        watchdog_enabled = 0;
+        if (!watchdog_disabled) {
+                watchdog_disabled = 1;
+                for_each_online_cpu(cpu)
+                        kthread_park(per_cpu(softlockup_watchdog, cpu));
+        }
 }
 
-
 /*
  * proc handler for /proc/sys/kernel/nmi_watchdog,watchdog_thresh
  */
@@ -557,73 +509,36 @@ int proc_dowatchdog(struct ctl_table *table, int write,
 {
         int ret;
 
+        if (watchdog_disabled < 0)
+                return -ENODEV;
+
         ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
         if (ret || !write)
-                goto out;
+                return ret;
 
         if (watchdog_enabled && watchdog_thresh)
                 watchdog_enable_all_cpus();
         else
                 watchdog_disable_all_cpus();
 
-out:
         return ret;
 }
 #endif /* CONFIG_SYSCTL */
 
-
-/*
- * Create/destroy watchdog threads as CPUs come and go:
- */
-static int __cpuinit
-cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
-{
-        int hotcpu = (unsigned long)hcpu;
-
-        switch (action) {
-        case CPU_UP_PREPARE:
-        case CPU_UP_PREPARE_FROZEN:
-                watchdog_prepare_cpu(hotcpu);
-                break;
-        case CPU_ONLINE:
-        case CPU_ONLINE_FROZEN:
-                if (watchdog_enabled)
-                        watchdog_enable(hotcpu);
-                break;
-#ifdef CONFIG_HOTPLUG_CPU
-        case CPU_UP_CANCELED:
-        case CPU_UP_CANCELED_FROZEN:
-                watchdog_disable(hotcpu);
-                break;
-        case CPU_DEAD:
-        case CPU_DEAD_FROZEN:
-                watchdog_disable(hotcpu);
-                break;
-#endif /* CONFIG_HOTPLUG_CPU */
-        }
-
-        /*
-         * hardlockup and softlockup are not important enough
-         * to block cpu bring up.  Just always succeed and
-         * rely on printk output to flag problems.
-         */
-        return NOTIFY_OK;
-}
-
-static struct notifier_block __cpuinitdata cpu_nfb = {
-        .notifier_call = cpu_callback
+static struct smp_hotplug_thread watchdog_threads = {
+        .store                  = &softlockup_watchdog,
+        .thread_should_run      = watchdog_should_run,
+        .thread_fn              = watchdog,
+        .thread_comm            = "watchdog/%u",
+        .setup                  = watchdog_enable,
+        .park                   = watchdog_disable,
+        .unpark                 = watchdog_enable,
 };
 
 void __init lockup_detector_init(void)
 {
-        void *cpu = (void *)(long)smp_processor_id();
-        int err;
-
-        err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
-        WARN_ON(notifier_to_errno(err));
-
-        cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
-        register_cpu_notifier(&cpu_nfb);
-
-        return;
+        if (smpboot_register_percpu_thread(&watchdog_threads)) {
+                pr_err("Failed to create watchdog threads, disabled\n");
+                watchdog_disabled = -ENODEV;
+        }
 }