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Subject[PATCHv3 0/4] watchdog_hld cleanup and async model for arm64
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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.

In this series, [1-2/4] are trivial cleanup. [3-4/4] is for this async
model.

v2 -> v3:
check the delay work waken up and flush the work before __initdata is free.
improve the commit log of [4/4]
rebase to v5.15-rc5

v1 > v2:
uplift the async model from hard lockup layer to watchdog layter.
The benefit is simpler code, the drawback is re-initialize means wasted
alloc/free.

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>
To: linux-arm-kernel@lists.infradead.org
To: linux-kernel@vger.kernel.org

*** BLURB HERE ***

Pingfan Liu (3):
kernel/watchdog: trival cleanups
kernel/watchdog_hld: Ensure CPU-bound context when creating hardlockup
detector event
kernel/watchdog: Adapt the watchdog_hld interface for async model

Sumit Garg (1):
arm64: Enable perf events based hard lockup detector

arch/arm64/Kconfig | 2 ++
arch/arm64/kernel/Makefile | 1 +
arch/arm64/kernel/perf_event.c | 11 ++++--
arch/arm64/kernel/watchdog_hld.c | 36 +++++++++++++++++++
arch/sparc/kernel/nmi.c | 8 ++---
drivers/perf/arm_pmu.c | 5 +++
include/linux/nmi.h | 11 +++++-
include/linux/perf/arm_pmu.h | 2 ++
kernel/watchdog.c | 62 ++++++++++++++++++++++++++++----
kernel/watchdog_hld.c | 5 ++-
10 files changed, 129 insertions(+), 14 deletions(-)
create mode 100644 arch/arm64/kernel/watchdog_hld.c

--
2.31.1

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