As we already used hld internally for arm64 since 2020, there still doesn't have a proper commit on the upstream and we badly need it. This serise rework on 5.17-rc7 from [1] and the origin author is Pingfan Liu <kernelfans@xxxxxxxxx> Sumit Garg <sumit.garg@xxxxxxxxxx> Qoute from [1]: > Hard lockup detector is helpful to diagnose unpaired irq enable/disable. > But the current watchdog framework can not cope with arm64 hw perf event > easily. > On arm64, when lockup_detector_init()->watchdog_nmi_probe(), 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 the > initialization of armv8_pmu_driver_init() 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. [1] https://lore.kernel.org/lkml/20211014024155.15253-1-kernelfans@xxxxxxxxx/ v2: 1. Tweak commit message in patch 01/02/04/05 2. Remove vobose WARN in patch 04 within watchdog core. 3. Change from three states variable: detector_delay_init_state to two states variable: lockup_detector_pending_init Thanks Petr Mladek <pmladek@xxxxxxxx> for the idea. > 1. lockup_detector_work() called before lockup_detector_check(). > In this case, wait_event() will wait until lockup_detector_check() > clears detector_delay_pending_init and calls wake_up(). > 2. lockup_detector_check() called before lockup_detector_work(). > In this case, wait_even() will immediately continue because > it will see cleared detector_delay_pending_init. 4. Add comment in code in patch 04/05 for two states variable changing. Lecopzer Chen (4): kernel/watchdog: remove WATCHDOG_DEFAULT kernel/watchdog: change watchdog_nmi_enable() to void kernel/watchdog: Adapt the watchdog_hld interface for async model arm64: Enable perf events based hard lockup detector Pingfan Liu (1): kernel/watchdog_hld: Ensure CPU-bound context when creating hardlockup detector event arch/arm64/Kconfig | 2 + arch/arm64/kernel/Makefile | 1 + arch/arm64/kernel/perf_event.c | 12 +++++- arch/sparc/kernel/nmi.c | 8 ++-- drivers/perf/arm_pmu.c | 5 +++ include/linux/nmi.h | 5 ++- include/linux/perf/arm_pmu.h | 2 + kernel/watchdog.c | 67 +++++++++++++++++++++++++++++++--- kernel/watchdog_hld.c | 8 +++- 9 files changed, 95 insertions(+), 15 deletions(-) -- 2.25.1
