[RFC patch 4/5] watchdog: Use hotplug thread infrastructure

Thomas Gleixner
2012-06-13T11:01:35Z

[-- Attachment #1: watchdog-use-smb-kthreads.patch --]
[-- Type: text/plain, Size: 9022 bytes --]

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/watchdog.c | 232 ++++++++++++++++--------------------------------------
1 file changed, 69 insertions(+), 163 deletions(-)

Index: tip/kernel/watchdog.c
===================================================================
--- tip.orig/kernel/watchdog.c
+++ tip/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>
@@ -29,6 +30,7 @@

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);
@@ -256,6 +258,9 @@ static void watchdog_interrupt_count(voi
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)
{
@@ -327,23 +332,46 @@ static enum hrtimer_restart watchdog_tim
return HRTIMER_RESTART;
}

-
-/*
- * The watchdog thread - touches the timestamp.
- */
-static int watchdog(void *unused)
+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();
+ /* 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);

+ /* initialize timestamp */
+ __touch_watchdog();
+}
+
+static void watchdog_disable(unsigned int cpu)
+{
+ struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
+
+ hrtimer_cancel(hrtimer);
+ /* disable the perf event */
+ watchdog_nmi_disable(cpu);
+}
+
+/*
+ * The watchdog thread - touches the timestamp.
+ */
+static int watchdog(void *td)
+{
+ struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };
+
+ if (!watchdog_enabled)
+ kthread_park(current);
+
+ sched_setscheduler(current, SCHED_FIFO, &param);
+
set_current_state(TASK_INTERRUPTIBLE);
/*
* Run briefly (kicked by the hrtimer callback function) once every
@@ -352,27 +380,16 @@ static int watchdog(void *unused)
* 2*watchdog_thresh seconds then the debug-printout triggers in
* watchdog_timer_fn().
*/
- while (!kthread_should_stop()) {
+ while (!smpboot_thread_check_parking(td)) {
+ set_current_state(TASK_INTERRUPTIBLE);
__touch_watchdog();
schedule();
-
- if (kthread_should_stop())
- break;
-
- 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;
}

-
#ifdef CONFIG_HARDLOCKUP_DETECTOR
-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);
@@ -395,7 +412,6 @@ static int watchdog_nmi_enable(int cpu)
goto out_save;
}

-
/* vary the KERN level based on the returned errno */
if (PTR_ERR(event) == -EOPNOTSUPP)
pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
@@ -416,7 +432,7 @@ 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);

@@ -430,107 +446,35 @@ 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;
+ unsigned int cpu;

- for_each_online_cpu(cpu)
- watchdog_disable(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
*/
@@ -540,73 +484,35 @@ int proc_dowatchdog(struct ctl_table *ta
{
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_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;
+ }
}