1 files changed, 75 insertions, 15 deletions

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index a8d6914030fe..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);
@@ -185,7 +208,7 @@ void touch_nmi_watchdog(void)
 	 * case we shouldn't have to worry about the watchdog
 	 * going off.
 	 */
-	__raw_get_cpu_var(watchdog_nmi_touch) = true;
+	raw_cpu_write(watchdog_nmi_touch, true);
 	touch_softlockup_watchdog();
 }
 EXPORT_SYMBOL(touch_nmi_watchdog);
@@ -194,8 +217,8 @@ EXPORT_SYMBOL(touch_nmi_watchdog);
 
 void touch_softlockup_watchdog_sync(void)
 {
-	__raw_get_cpu_var(softlockup_touch_sync) = true;
-	__raw_get_cpu_var(watchdog_touch_ts) = 0;
+	__this_cpu_write(softlockup_touch_sync, true);
+	__this_cpu_write(watchdog_touch_ts, 0);
 }
 
 #ifdef CONFIG_HARDLOCKUP_DETECTOR
@@ -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)
@@ -387,7 +425,7 @@ static void watchdog_set_prio(unsigned int policy, unsigned int prio)
 
 static void watchdog_enable(unsigned int cpu)
 {
-	struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
+	struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer);
 
 	/* kick off the timer for the hardlockup detector */
 	hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
@@ -407,7 +445,7 @@ static void watchdog_enable(unsigned int cpu)
 
 static void watchdog_disable(unsigned int cpu)
 {
-	struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
+	struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer);
 
 	watchdog_set_prio(SCHED_NORMAL, 0);
 	hrtimer_cancel(hrtimer);
@@ -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; }
@@ -534,7 +585,7 @@ static struct smp_hotplug_thread watchdog_threads = {
 
 static void restart_watchdog_hrtimer(void *info)
 {
-	struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
+	struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer);
 	int ret;
 
 	/*
@@ -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);