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Diffstat (limited to 'kernel/watchdog.c')
-rw-r--r--kernel/watchdog.c78
1 files changed, 69 insertions, 9 deletions
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index dca8cae7e55d..70bf11815f84 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -15,11 +15,6 @@
#include <linux/cpu.h>
#include <linux/nmi.h>
#include <linux/init.h>
-#include <linux/delay.h>
-#include <linux/freezer.h>
-#include <linux/kthread.h>
-#include <linux/lockdep.h>
-#include <linux/notifier.h>
#include <linux/module.h>
#include <linux/sysctl.h>
#include <linux/smpboot.h>
@@ -47,6 +42,7 @@ 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);
+static DEFINE_PER_CPU(struct task_struct *, softlockup_task_ptr_saved);
#ifdef CONFIG_HARDLOCKUP_DETECTOR
static DEFINE_PER_CPU(bool, hard_watchdog_warn);
static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
@@ -63,6 +59,25 @@ static unsigned long soft_lockup_nmi_warn;
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
+ * cases this function can be called to disable hard lockup detection. This
+ * function should only be executed once by the boot processor before the
+ * 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)
+{
+ return hardlockup_detector_enabled;
+}
+
static int __init hardlockup_panic_setup(char *str)
{
if (!strncmp(str, "panic", 5))
@@ -71,6 +86,14 @@ static int __init hardlockup_panic_setup(char *str)
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);
+ }
return 1;
}
__setup("nmi_watchdog=", hardlockup_panic_setup);
@@ -333,8 +356,22 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
return HRTIMER_RESTART;
/* only warn once */
- if (__this_cpu_read(soft_watchdog_warn) == true)
+ if (__this_cpu_read(soft_watchdog_warn) == true) {
+ /*
+ * When multiple processes are causing softlockups the
+ * softlockup detector only warns on the first one
+ * because the code relies on a full quiet cycle to
+ * re-arm. The second process prevents the quiet cycle
+ * and never gets reported. Use task pointers to detect
+ * this.
+ */
+ if (__this_cpu_read(softlockup_task_ptr_saved) !=
+ current) {
+ __this_cpu_write(soft_watchdog_warn, false);
+ __touch_watchdog();
+ }
return HRTIMER_RESTART;
+ }
if (softlockup_all_cpu_backtrace) {
/* Prevent multiple soft-lockup reports if one cpu is already
@@ -350,6 +387,7 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
smp_processor_id(), duration,
current->comm, task_pid_nr(current));
+ __this_cpu_write(softlockup_task_ptr_saved, current);
print_modules();
print_irqtrace_events(current);
if (regs)
@@ -454,6 +492,15 @@ static int watchdog_nmi_enable(unsigned int cpu)
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;
+ }
+
/* is it already setup and enabled? */
if (event && event->state > PERF_EVENT_STATE_OFF)
goto out;
@@ -468,6 +515,7 @@ static int watchdog_nmi_enable(unsigned int cpu)
/* 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);
@@ -514,7 +562,10 @@ static void watchdog_nmi_disable(unsigned int cpu)
/* should be in cleanup, but blocks oprofile */
perf_event_release_kernel(event);
}
- return;
+ if (cpu == 0) {
+ /* watchdog_nmi_enable() expects this to be zero initially. */
+ cpu0_err = 0;
+ }
}
#else
static int watchdog_nmi_enable(unsigned int cpu) { return 0; }
@@ -610,11 +661,13 @@ int proc_dowatchdog(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);
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)
@@ -626,15 +679,22 @@ int proc_dowatchdog(struct ctl_table *table, int write,
* disabled. The 'watchdog_running' variable check in
* watchdog_*_all_cpus() function takes care of this.
*/
- if (watchdog_user_enabled && watchdog_thresh)
+ if (watchdog_user_enabled && watchdog_thresh) {
+ /*
+ * Prevent a change in watchdog_thresh accidentally overriding
+ * the enablement of the hardlockup detector.
+ */
+ if (watchdog_user_enabled != old_enabled)
+ watchdog_enable_hardlockup_detector(true);
err = watchdog_enable_all_cpus(old_thresh != watchdog_thresh);
- else
+ } else
watchdog_disable_all_cpus();
/* Restore old values on failure */
if (err) {
watchdog_thresh = old_thresh;
watchdog_user_enabled = old_enabled;
+ watchdog_enable_hardlockup_detector(old_hardlockup);
}
out:
mutex_unlock(&watchdog_proc_mutex);