@@ -118,6 +118,15 @@ static inline int hardlockup_detector_perf_init(void) { return 0; }
void watchdog_nmi_stop(void);
void watchdog_nmi_start(void);
+
+enum hld_detector_state {
+ DELAY_INIT_NOP,
+ DELAY_INIT_WAIT,
+ DELAY_INIT_READY
+};
+
+extern enum hld_detector_state detector_delay_init_state;
+extern struct wait_queue_head hld_detector_wait;
int watchdog_nmi_probe(void);
void watchdog_nmi_enable(unsigned int cpu);
void watchdog_nmi_disable(unsigned int cpu);
@@ -103,7 +103,11 @@ void __weak watchdog_nmi_disable(unsigned int cpu)
hardlockup_detector_perf_disable();
}
-/* Return 0, if a NMI watchdog is available. Error code otherwise */
+/*
+ * Arch specific API. Return 0, if a NMI watchdog is available. -EBUSY if not
+ * ready, and arch code should wake up hld_detector_wait when ready. Other
+ * negative value if not support.
+ */
int __weak __init watchdog_nmi_probe(void)
{
return hardlockup_detector_perf_init();
@@ -739,15 +743,64 @@ int proc_watchdog_cpumask(struct ctl_table *table, int write,
}
#endif /* CONFIG_SYSCTL */
+static void lockup_detector_delay_init(struct work_struct *work);
+enum hld_detector_state detector_delay_init_state __initdata;
+
+struct wait_queue_head hld_detector_wait __initdata =
+ __WAIT_QUEUE_HEAD_INITIALIZER(hld_detector_wait);
+
+static struct work_struct detector_work __initdata =
+ __WORK_INITIALIZER(detector_work, lockup_detector_delay_init);
+
+static void __init lockup_detector_delay_init(struct work_struct *work)
+{
+ int ret;
+
+ wait_event(hld_detector_wait,
+ detector_delay_init_state == DELAY_INIT_READY);
+ ret = watchdog_nmi_probe();
+ if (!ret) {
+ nmi_watchdog_available = true;
+ lockup_detector_setup();
+ } else {
+ WARN_ON(ret == -EBUSY);
+ pr_info("Perf NMI watchdog permanently disabled\n");
+ }
+}
+
+/* Ensure the check is called after the initialization of PMU driver */
+static int __init lockup_detector_check(void)
+{
+ if (detector_delay_init_state < DELAY_INIT_WAIT)
+ return 0;
+
+ if (WARN_ON(detector_delay_init_state == DELAY_INIT_WAIT)) {
+ detector_delay_init_state = DELAY_INIT_READY;
+ wake_up(&hld_detector_wait);
+ }
+ flush_work(&detector_work);
+ return 0;
+}
+late_initcall_sync(lockup_detector_check);
+
+
void __init lockup_detector_init(void)
{
+ int ret;
+
if (tick_nohz_full_enabled())
pr_info("Disabling watchdog on nohz_full cores by default\n");
cpumask_copy(&watchdog_cpumask,
housekeeping_cpumask(HK_FLAG_TIMER));
- if (!watchdog_nmi_probe())
+ ret = watchdog_nmi_probe();
+ if (!ret)
nmi_watchdog_available = true;
+ else if (ret == -EBUSY) {
+ detector_delay_init_state = DELAY_INIT_WAIT;
+ queue_work_on(smp_processor_id(), system_wq, &detector_work);
+ }
+
lockup_detector_setup();
}
When lockup_detector_init()->watchdog_nmi_probe(), PMU may be not ready yet. E.g. on arm64, PMU is not ready until device_initcall(armv8_pmu_driver_init). And it is deeply integrated with the driver model and cpuhp. Hence it is hard to push this initialization before smp_init(). But it is easy to take an opposite approach by enabling watchdog_hld to get the capability of PMU async. The async model is achieved by expanding watchdog_nmi_probe() with -EBUSY, and a re-initializing work_struct which waits on a wait_queue_head. Signed-off-by: Pingfan Liu <kernelfans@gmail.com> Cc: Sumit Garg <sumit.garg@linaro.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Marc Zyngier <maz@kernel.org> Cc: Kees Cook <keescook@chromium.org> Cc: Masahiro Yamada <masahiroy@kernel.org> Cc: Sami Tolvanen <samitolvanen@google.com> Cc: Petr Mladek <pmladek@suse.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Wang Qing <wangqing@vivo.com> Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org> Cc: Santosh Sivaraj <santosh@fossix.org> Cc: linux-arm-kernel@lists.infradead.org To: linux-kernel@vger.kernel.org --- include/linux/nmi.h | 9 +++++++ kernel/watchdog.c | 57 +++++++++++++++++++++++++++++++++++++++++++-- 2 files changed, 64 insertions(+), 2 deletions(-)