Messages in this thread Patch in this message | | | From | Pingfan Liu <> | Subject | [PATCHv3 3/4] kernel/watchdog: Adapt the watchdog_hld interface for async model | Date | Thu, 14 Oct 2021 10:41:54 +0800 |
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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(-)
diff --git a/include/linux/nmi.h b/include/linux/nmi.h index b7bcd63c36b4..9def85c00bd8 100644 --- a/include/linux/nmi.h +++ b/include/linux/nmi.h @@ -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); diff --git a/kernel/watchdog.c b/kernel/watchdog.c index 6e6dd5f0bc3e..2f267d21a7a1 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -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(); } -- 2.31.1
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