+ watchdog-hardlockup-add-comments-to-touch_nmi_watchdog.patch added to mm-nonmm-unstable branch

+ watchdog-hardlockup-add-comments-to-touch_nmi_watchdog.patch added to mm-nonmm-unstable branch

[Andrew Morton]

The patch titled
     Subject: watchdog/hardlockup: add comments to touch_nmi_watchdog()
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     watchdog-hardlockup-add-comments-to-touch_nmi_watchdog.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/watchdog-hardlockup-add-comments-to-touch_nmi_watchdog.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Douglas Anderson <dianders@chromium.org>
Subject: watchdog/hardlockup: add comments to touch_nmi_watchdog()
Date: Fri, 19 May 2023 10:18:30 -0700

In preparation for the buddy hardlockup detector, add comments to
touch_nmi_watchdog() to make it obvious that it touches the configured
hardlockup detector regardless of whether it's backed by an NMI.  Also
note that arch_touch_nmi_watchdog() may not be architecture-specific.

Ideally, we'd like to rename these functions but that is a fairly
disruptive change touching a lot of drivers.  After discussion [1] the
plan is to defer this until a good time.

[1] https://lore.kernel.org/r/ZFy0TX1tfhlH8gxj@alley

Link: https://lkml.kernel.org/r/20230519101840.v5.6.I4e47cbfa1bb2ebbcdb5ca16817aa2887f15dc82c@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Colin Cross <ccross@android.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>
Cc: Matthias Kaehlcke <mka@chromium.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Stephen Boyd <swboyd@chromium.org>
Cc: Sumit Garg <sumit.garg@linaro.org>
Cc: Tzung-Bi Shih <tzungbi@chromium.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/nmi.h |   23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

--- a/include/linux/nmi.h~watchdog-hardlockup-add-comments-to-touch_nmi_watchdog
+++ a/include/linux/nmi.h
@@ -125,15 +125,30 @@ void watchdog_nmi_disable(unsigned int c
 void lockup_detector_reconfigure(void);
 
 /**
- * touch_nmi_watchdog - restart NMI watchdog timeout.
+ * touch_nmi_watchdog - manually pet the hardlockup watchdog.
  *
- * If the architecture supports the NMI watchdog, touch_nmi_watchdog()
- * may be used to reset the timeout - for code which intentionally
- * disables interrupts for a long time. This call is stateless.
+ * If we support detecting hardlockups, touch_nmi_watchdog() may be
+ * used to pet the watchdog (reset the timeout) - for code which
+ * intentionally disables interrupts for a long time. This call is stateless.
+ *
+ * Though this function has "nmi" in the name, the hardlockup watchdog might
+ * not be backed by NMIs. This function will likely be renamed to
+ * touch_hardlockup_watchdog() in the future.
  */
 static inline void touch_nmi_watchdog(void)
 {
+	/*
+	 * Pass on to the hardlockup detector selected via CONFIG_. Note that
+	 * the hardlockup detector may not be arch-specific nor using NMIs
+	 * and the arch_touch_nmi_watchdog() function will likely be renamed
+	 * in the future.
+	 */
 	arch_touch_nmi_watchdog();
+
+	/*
+	 * Touching the hardlock detector implcitily pets the
+	 * softlockup detector too
+	 */
 	touch_softlockup_watchdog();
 }
 
_

Patches currently in -mm which might be from dianders@chromium.org are

migrate_pages-avoid-blocking-for-io-in-migrate_sync_light.patch
watchdog-perf-define-dummy-watchdog_update_hrtimer_threshold-on-correct-config.patch
watchdog-perf-more-properly-prevent-false-positives-with-turbo-modes.patch
watchdog-hardlockup-add-comments-to-touch_nmi_watchdog.patch
watchdog-perf-rename-watchdog_hldc-to-watchdog_perfc.patch
watchdog-hardlockup-move-perf-hardlockup-checking-panic-to-common-watchdogc.patch
watchdog-hardlockup-style-changes-to-watchdog_hardlockup_check-is_hardlockup.patch
watchdog-hardlockup-add-a-cpu-param-to-watchdog_hardlockup_check.patch
watchdog-hardlockup-move-perf-hardlockup-watchdog-petting-to-watchdogc.patch
watchdog-hardlockup-rename-some-nmi-watchdog-constants-function.patch
watchdog-hardlockup-have-the-perf-hardlockup-use-__weak-functions-more-cleanly.patch
watchdog-hardlockup-detect-hard-lockups-using-secondary-buddy-cpus.patch
watchdog-perf-add-a-weak-function-for-an-arch-to-detect-if-perf-can-use-nmis.patch
arm64-enable-perf-events-based-hard-lockup-detector.patch