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

[Lecopzer Chen]

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@xxxxxxxxx>
Sumit Garg <sumit.garg@xxxxxxxxxx>

[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@xxxxxxxxx/


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

-- 
2.25.1