[PATCH 0/5] Support hld based on Pseudo-NMI for arm64

Lecopzer Chen
2022-02-12T10:44:16Z

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 rebase on 5.17-rc3 from [1] and the origin author is
Pingfan Liu <kernelfans@gmail.com>
Sumit Garg <sumit.garg@linaro.org>

[1] wasn't reviewed for its patch v3, I'll take over the further development
for this.

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@gmail.com/

Lecopzer Chen (2):
kernel/watchdog: remove WATCHDOG_DEFAULT
kernel/watchdog: change watchdog_nmi_enable() to void

Pingfan Liu (2):
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 | 61 ++++++++++++++++++++++++++++----
kernel/watchdog_hld.c | 8 ++++-
10 files changed, 131 insertions(+), 14 deletions(-)
create mode 100644 arch/arm64/kernel/watchdog_hld.c

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2.25.1