[PATCHv2 0/4] watchdog_hld cleanup and async model for arm64

From: Pingfan Liu
Date: Thu Sep 23 2021 - 10:10:22 EST


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
modification.)

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
wait_queue_head.

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


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.

[1]: http://lore.kernel.org/linux-arm-kernel/1610712101-14929-1-git-send-email-sumit.garg@xxxxxxxxxx

Cc: Sumit Garg <sumit.garg@xxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Marc Zyngier <maz@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Cc: Sami Tolvanen <samitolvanen@xxxxxxxxxx>
Cc: Petr Mladek <pmladek@xxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Wang Qing <wangqing@xxxxxxxx>
Cc: "Peter Zijlstra (Intel)" <peterz@xxxxxxxxxxxxx>
Cc: Santosh Sivaraj <santosh@xxxxxxxxxx>
To: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
To: linux-kernel@xxxxxxxxxxxxxxx

*** BLURB HERE ***

Pingfan Liu (3):
kernel/watchdog: trival cleanups
kernel/watchdog_hld: clarify the condition in
hardlockup_detector_event_create()
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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2.31.1