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Date:   Thu, 23 Sep 2021 22:09:47 +0800
From:   Pingfan Liu <>
Cc:     Pingfan Liu <>,
        Sumit Garg <>,
        Catalin Marinas <>,
        Will Deacon <>, Ingo Molnar <>,
        Arnaldo Carvalho de Melo <>,
        Mark Rutland <>,
        Alexander Shishkin <>,
        Jiri Olsa <>,
        Namhyung Kim <>,
        Marc Zyngier <>,
        Kees Cook <>,
        Masahiro Yamada <>,
        Sami Tolvanen <>,
        Petr Mladek <>,
        Andrew Morton <>,
        Wang Qing <>,
        "Peter Zijlstra (Intel)" <>,
        Santosh Sivaraj <>
Subject: [PATCHv2 0/4] watchdog_hld cleanup and async model for arm64

hard lockup detector is helpful to diagnose unpaired irq enable/disable.
Sumit has tried with a series, and the last one is V5 [1].
Since it lasts a long time without any update, I takes a retry, which
addresses the delay intialization of watchdog_hld.
( To: Sumit, I think the main body of [4/4] is contributed from you,so I
keep you as the author, please let me know if you dislike it and my

There is an obstacle to integrate arm64 hw perf event into watchdog_hld.
When lockup_detector_init()->watchdog_nmi_probe(), 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
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

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

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

Cc: Sumit Garg <>
Cc: Catalin Marinas <>
Cc: Will Deacon <>
Cc: Ingo Molnar <>
Cc: Arnaldo Carvalho de Melo <>
Cc: Mark Rutland <>
Cc: Alexander Shishkin <>
Cc: Jiri Olsa <>
Cc: Namhyung Kim <>
Cc: Marc Zyngier <>
Cc: Kees Cook <>
Cc: Masahiro Yamada <>
Cc: Sami Tolvanen <>
Cc: Petr Mladek <>
Cc: Andrew Morton <>
Cc: Wang Qing <>
Cc: "Peter Zijlstra (Intel)" <>
Cc: Santosh Sivaraj <>

*** BLURB HERE ***

Pingfan Liu (3):
  kernel/watchdog: trival cleanups
  kernel/watchdog_hld: clarify the condition in
  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 +++++++++++++++++++++++++++
 drivers/perf/arm_pmu.c           |  5 ++++
 include/linux/nmi.h              |  5 +++-
 include/linux/perf/arm_pmu.h     |  2 ++
 kernel/watchdog.c                | 42 +++++++++++++++++++++++++++-----
 kernel/watchdog_hld.c            |  5 +++-
 9 files changed, 99 insertions(+), 10 deletions(-)
 create mode 100644 arch/arm64/kernel/watchdog_hld.c


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