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-rw-r--r--kernel/watchdog.c34
1 files changed, 20 insertions, 14 deletions
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 7c397907d0e9..92d3bcc5a5e0 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -302,10 +302,10 @@ void touch_softlockup_watchdog_sync(void)
__this_cpu_write(watchdog_report_ts, SOFTLOCKUP_DELAY_REPORT);
}
-static int is_softlockup(unsigned long touch_ts, unsigned long period_ts)
+static int is_softlockup(unsigned long touch_ts,
+ unsigned long period_ts,
+ unsigned long now)
{
- unsigned long now = get_timestamp();
-
if ((watchdog_enabled & SOFT_WATCHDOG_ENABLED) && watchdog_thresh){
/* Warn about unreasonable delays. */
if (time_after(now, period_ts + get_softlockup_thresh()))
@@ -353,8 +353,7 @@ static int softlockup_fn(void *data)
/* watchdog kicker functions */
static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
{
- unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
- unsigned long period_ts = __this_cpu_read(watchdog_report_ts);
+ unsigned long touch_ts, period_ts, now;
struct pt_regs *regs = get_irq_regs();
int duration;
int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
@@ -377,11 +376,22 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
/*
+ * Read the current timestamp first. It might become invalid anytime
+ * when a virtual machine is stopped by the host or when the watchog
+ * is touched from NMI.
+ */
+ now = get_timestamp();
+ /*
* If a virtual machine is stopped by the host it can look to
- * the watchdog like a soft lockup. Check to see if the host
- * stopped the vm before we process the timestamps.
+ * the watchdog like a soft lockup. This function touches the watchdog.
*/
kvm_check_and_clear_guest_paused();
+ /*
+ * The stored timestamp is comparable with @now only when not touched.
+ * It might get touched anytime from NMI. Make sure that is_softlockup()
+ * uses the same (valid) value.
+ */
+ period_ts = READ_ONCE(*this_cpu_ptr(&watchdog_report_ts));
/* Reset the interval when touched by known problematic code. */
if (period_ts == SOFTLOCKUP_DELAY_REPORT) {
@@ -398,13 +408,9 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
return HRTIMER_RESTART;
}
- /* check for a softlockup
- * This is done by making sure a high priority task is
- * being scheduled. The task touches the watchdog to
- * indicate it is getting cpu time. If it hasn't then
- * this is a good indication some task is hogging the cpu
- */
- duration = is_softlockup(touch_ts, period_ts);
+ /* Check for a softlockup. */
+ touch_ts = __this_cpu_read(watchdog_touch_ts);
+ duration = is_softlockup(touch_ts, period_ts, now);
if (unlikely(duration)) {
/*
* Prevent multiple soft-lockup reports if one cpu is already