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-rw-r--r--kernel/watchdog.c30
1 files changed, 30 insertions, 0 deletions
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 26002ed4c16e..fd2b6dc14486 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -502,6 +502,21 @@ static void watchdog(unsigned int cpu)
__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
@@ -552,6 +567,18 @@ handle_err:
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);
@@ -565,6 +592,9 @@ handle_err:
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 */