#include <linux/kvm_para.h>
#include <linux/perf_event.h>
-int watchdog_user_enabled = 1;
+/*
+ * The run state of the lockup detectors is controlled by the content of the
+ * 'watchdog_enabled' variable. Each lockup detector has its dedicated bit -
+ * bit 0 for the hard lockup detector and bit 1 for the soft lockup detector.
+ *
+ * 'watchdog_user_enabled', 'nmi_watchdog_enabled' and 'soft_watchdog_enabled'
+ * are variables that are only used as an 'interface' between the parameters
+ * in /proc/sys/kernel and the internal state bits in 'watchdog_enabled'. The
+ * 'watchdog_thresh' variable is handled differently because its value is not
+ * boolean, and the lockup detectors are 'suspended' while 'watchdog_thresh'
+ * is equal zero.
+ */
+#define NMI_WATCHDOG_ENABLED_BIT 0
+#define SOFT_WATCHDOG_ENABLED_BIT 1
+#define NMI_WATCHDOG_ENABLED (1 << NMI_WATCHDOG_ENABLED_BIT)
+#define SOFT_WATCHDOG_ENABLED (1 << SOFT_WATCHDOG_ENABLED_BIT)
+
+#ifdef CONFIG_HARDLOCKUP_DETECTOR
+static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED|NMI_WATCHDOG_ENABLED;
+#else
+static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED;
+#endif
+int __read_mostly nmi_watchdog_enabled;
+int __read_mostly soft_watchdog_enabled;
+int __read_mostly watchdog_user_enabled;
int __read_mostly watchdog_thresh = 10;
+
#ifdef CONFIG_SMP
int __read_mostly sysctl_softlockup_all_cpu_backtrace;
#else
#ifdef CONFIG_HARDLOCKUP_DETECTOR
static int hardlockup_panic =
CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
-
-static bool hardlockup_detector_enabled = true;
/*
* We may not want to enable hard lockup detection by default in all cases,
* for example when running the kernel as a guest on a hypervisor. In these
* kernel command line parameters are parsed, because otherwise it is not
* possible to override this in hardlockup_panic_setup().
*/
-void watchdog_enable_hardlockup_detector(bool val)
-{
- hardlockup_detector_enabled = val;
-}
-
-bool watchdog_hardlockup_detector_is_enabled(void)
+void hardlockup_detector_disable(void)
{
- return hardlockup_detector_enabled;
+ watchdog_enabled &= ~NMI_WATCHDOG_ENABLED;
}
static int __init hardlockup_panic_setup(char *str)
else if (!strncmp(str, "nopanic", 7))
hardlockup_panic = 0;
else if (!strncmp(str, "0", 1))
- watchdog_user_enabled = 0;
- else if (!strncmp(str, "1", 1) || !strncmp(str, "2", 1)) {
- /*
- * Setting 'nmi_watchdog=1' or 'nmi_watchdog=2' (legacy option)
- * has the same effect.
- */
- watchdog_user_enabled = 1;
- watchdog_enable_hardlockup_detector(true);
- }
+ watchdog_enabled &= ~NMI_WATCHDOG_ENABLED;
+ else if (!strncmp(str, "1", 1))
+ watchdog_enabled |= NMI_WATCHDOG_ENABLED;
return 1;
}
__setup("nmi_watchdog=", hardlockup_panic_setup);
static int __init nowatchdog_setup(char *str)
{
- watchdog_user_enabled = 0;
+ watchdog_enabled = 0;
return 1;
}
__setup("nowatchdog", nowatchdog_setup);
-/* deprecated */
static int __init nosoftlockup_setup(char *str)
{
- watchdog_user_enabled = 0;
+ watchdog_enabled &= ~SOFT_WATCHDOG_ENABLED;
return 1;
}
__setup("nosoftlockup", nosoftlockup_setup);
-/* */
+
#ifdef CONFIG_SMP
static int __init softlockup_all_cpu_backtrace_setup(char *str)
{
{
unsigned long now = get_timestamp();
- /* Warn about unreasonable delays: */
- if (time_after(now, touch_ts + get_softlockup_thresh()))
- return now - touch_ts;
-
+ if (watchdog_enabled & SOFT_WATCHDOG_ENABLED) {
+ /* Warn about unreasonable delays. */
+ if (time_after(now, touch_ts + get_softlockup_thresh()))
+ return now - touch_ts;
+ }
return 0;
}
__this_cpu_write(soft_lockup_hrtimer_cnt,
__this_cpu_read(hrtimer_interrupts));
__touch_watchdog();
+
+ /*
+ * watchdog_nmi_enable() clears the NMI_WATCHDOG_ENABLED bit in the
+ * failure path. Check for failures that can occur asynchronously -
+ * for example, when CPUs are on-lined - and shut down the hardware
+ * perf event on each CPU accordingly.
+ *
+ * The only non-obvious place this bit can be cleared is through
+ * watchdog_nmi_enable(), so a pr_info() is placed there. Placing a
+ * pr_info here would be too noisy as it would result in a message
+ * every few seconds if the hardlockup was disabled but the softlockup
+ * enabled.
+ */
+ if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
+ watchdog_nmi_disable(cpu);
}
#ifdef CONFIG_HARDLOCKUP_DETECTOR
struct perf_event_attr *wd_attr;
struct perf_event *event = per_cpu(watchdog_ev, cpu);
- /*
- * Some kernels need to default hard lockup detection to
- * 'disabled', for example a guest on a hypervisor.
- */
- if (!watchdog_hardlockup_detector_is_enabled()) {
- event = ERR_PTR(-ENOENT);
- goto handle_err;
- }
+ /* 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)
/* Try to register using hardware perf events */
event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);
-handle_err:
/* save cpu0 error for future comparision */
if (cpu == 0 && IS_ERR(event))
cpu0_err = PTR_ERR(event);
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);
else
pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
cpu, PTR_ERR(event));
+
+ pr_info("Shutting down hard lockup detector on all cpus\n");
+
return PTR_ERR(event);
/* success path */
cpu0_err = 0;
}
}
+
+void watchdog_nmi_enable_all(void)
+{
+ int cpu;
+
+ if (!watchdog_user_enabled)
+ return;
+
+ get_online_cpus();
+ for_each_online_cpu(cpu)
+ watchdog_nmi_enable(cpu);
+ put_online_cpus();
+}
+
+void watchdog_nmi_disable_all(void)
+{
+ int cpu;
+
+ if (!watchdog_running)
+ return;
+
+ get_online_cpus();
+ for_each_online_cpu(cpu)
+ watchdog_nmi_disable(cpu);
+ put_online_cpus();
+}
#else
static int watchdog_nmi_enable(unsigned int cpu) { return 0; }
static void watchdog_nmi_disable(unsigned int cpu) { return; }
+void watchdog_nmi_enable_all(void) {}
+void watchdog_nmi_disable_all(void) {}
#endif /* CONFIG_HARDLOCKUP_DETECTOR */
static struct smp_hotplug_thread watchdog_threads = {
HRTIMER_MODE_REL_PINNED);
}
-static void update_timers(int cpu)
+static void update_watchdog(int cpu)
{
/*
* Make sure that perf event counter will adopt to a new
watchdog_nmi_enable(cpu);
}
-static void update_timers_all_cpus(void)
+static void update_watchdog_all_cpus(void)
{
int cpu;
get_online_cpus();
for_each_online_cpu(cpu)
- update_timers(cpu);
+ update_watchdog(cpu);
put_online_cpus();
}
-static int watchdog_enable_all_cpus(bool sample_period_changed)
+static int watchdog_enable_all_cpus(void)
{
int err = 0;
pr_err("Failed to create watchdog threads, disabled\n");
else
watchdog_running = 1;
- } else if (sample_period_changed) {
- update_timers_all_cpus();
+ } else {
+ /*
+ * Enable/disable the lockup detectors or
+ * change the sample period 'on the fly'.
+ */
+ update_watchdog_all_cpus();
}
return err;
}
/*
- * proc handler for /proc/sys/kernel/nmi_watchdog,watchdog_thresh
+ * Update the run state of the lockup detectors.
*/
+static int proc_watchdog_update(void)
+{
+ int err = 0;
-int proc_dowatchdog(struct ctl_table *table, int write,
- void __user *buffer, size_t *lenp, loff_t *ppos)
+ /*
+ * Watchdog threads won't be started if they are already active.
+ * The 'watchdog_running' variable in watchdog_*_all_cpus() takes
+ * care of this. If those threads are already active, the sample
+ * period will be updated and the lockup detectors will be enabled
+ * or disabled 'on the fly'.
+ */
+ if (watchdog_enabled && watchdog_thresh)
+ err = watchdog_enable_all_cpus();
+ else
+ watchdog_disable_all_cpus();
+
+ return err;
+
+}
+
+static DEFINE_MUTEX(watchdog_proc_mutex);
+
+/*
+ * common function for watchdog, nmi_watchdog and soft_watchdog parameter
+ *
+ * caller | table->data points to | 'which' contains the flag(s)
+ * -------------------|-----------------------|-----------------------------
+ * proc_watchdog | watchdog_user_enabled | NMI_WATCHDOG_ENABLED or'ed
+ * | | with SOFT_WATCHDOG_ENABLED
+ * -------------------|-----------------------|-----------------------------
+ * proc_nmi_watchdog | nmi_watchdog_enabled | NMI_WATCHDOG_ENABLED
+ * -------------------|-----------------------|-----------------------------
+ * proc_soft_watchdog | soft_watchdog_enabled | SOFT_WATCHDOG_ENABLED
+ */
+static int proc_watchdog_common(int which, struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
{
- int err, old_thresh, old_enabled;
- bool old_hardlockup;
- static DEFINE_MUTEX(watchdog_proc_mutex);
+ int err, old, new;
+ int *watchdog_param = (int *)table->data;
mutex_lock(&watchdog_proc_mutex);
- old_thresh = ACCESS_ONCE(watchdog_thresh);
- old_enabled = ACCESS_ONCE(watchdog_user_enabled);
- old_hardlockup = watchdog_hardlockup_detector_is_enabled();
- err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
- if (err || !write)
- goto out;
-
- set_sample_period();
/*
- * Watchdog threads shouldn't be enabled if they are
- * disabled. The 'watchdog_running' variable check in
- * watchdog_*_all_cpus() function takes care of this.
+ * If the parameter is being read return the state of the corresponding
+ * bit(s) in 'watchdog_enabled', else update 'watchdog_enabled' and the
+ * run state of the lockup detectors.
*/
- if (watchdog_user_enabled && watchdog_thresh) {
+ if (!write) {
+ *watchdog_param = (watchdog_enabled & which) != 0;
+ err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+ } else {
+ err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+ if (err)
+ goto out;
+
/*
- * Prevent a change in watchdog_thresh accidentally overriding
- * the enablement of the hardlockup detector.
+ * There is a race window between fetching the current value
+ * from 'watchdog_enabled' and storing the new value. During
+ * this race window, watchdog_nmi_enable() can sneak in and
+ * clear the NMI_WATCHDOG_ENABLED bit in 'watchdog_enabled'.
+ * The 'cmpxchg' detects this race and the loop retries.
*/
- if (watchdog_user_enabled != old_enabled)
- watchdog_enable_hardlockup_detector(true);
- err = watchdog_enable_all_cpus(old_thresh != watchdog_thresh);
- } else
- watchdog_disable_all_cpus();
+ do {
+ old = watchdog_enabled;
+ /*
+ * If the parameter value is not zero set the
+ * corresponding bit(s), else clear it(them).
+ */
+ if (*watchdog_param)
+ new = old | which;
+ else
+ new = old & ~which;
+ } while (cmpxchg(&watchdog_enabled, old, new) != old);
- /* Restore old values on failure */
- if (err) {
- watchdog_thresh = old_thresh;
- watchdog_user_enabled = old_enabled;
- watchdog_enable_hardlockup_detector(old_hardlockup);
+ /*
+ * Update the run state of the lockup detectors.
+ * Restore 'watchdog_enabled' on failure.
+ */
+ err = proc_watchdog_update();
+ if (err)
+ watchdog_enabled = old;
}
out:
mutex_unlock(&watchdog_proc_mutex);
return err;
}
+
+/*
+ * /proc/sys/kernel/watchdog
+ */
+int proc_watchdog(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED,
+ table, write, buffer, lenp, ppos);
+}
+
+/*
+ * /proc/sys/kernel/nmi_watchdog
+ */
+int proc_nmi_watchdog(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ return proc_watchdog_common(NMI_WATCHDOG_ENABLED,
+ table, write, buffer, lenp, ppos);
+}
+
+/*
+ * /proc/sys/kernel/soft_watchdog
+ */
+int proc_soft_watchdog(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ return proc_watchdog_common(SOFT_WATCHDOG_ENABLED,
+ table, write, buffer, lenp, ppos);
+}
+
+/*
+ * /proc/sys/kernel/watchdog_thresh
+ */
+int proc_watchdog_thresh(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ int err, old;
+
+ mutex_lock(&watchdog_proc_mutex);
+
+ old = ACCESS_ONCE(watchdog_thresh);
+ err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+
+ if (err || !write)
+ goto out;
+
+ /*
+ * Update the sample period.
+ * Restore 'watchdog_thresh' on failure.
+ */
+ set_sample_period();
+ err = proc_watchdog_update();
+ if (err)
+ watchdog_thresh = old;
+out:
+ mutex_unlock(&watchdog_proc_mutex);
+ return err;
+}
#endif /* CONFIG_SYSCTL */
void __init lockup_detector_init(void)
{
set_sample_period();
- if (watchdog_user_enabled)
- watchdog_enable_all_cpus(false);
+ if (watchdog_enabled)
+ watchdog_enable_all_cpus();
}
projects / deliverable / linux.git / blobdiff