+ watchdog-hardlockup-have_nmi_watchdog-must-implement-watchdog_hardlockup_probe.patch added to mm-nonmm-unstable branch

+ watchdog-hardlockup-have_nmi_watchdog-must-implement-watchdog_hardlockup_probe.patch added to mm-nonmm-unstable branch

[Andrew Morton]

The patch titled
     Subject: watchdog/hardlockup: HAVE_NMI_WATCHDOG must implement watchdog_hardlockup_probe()
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     watchdog-hardlockup-have_nmi_watchdog-must-implement-watchdog_hardlockup_probe.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/watchdog-hardlockup-have_nmi_watchdog-must-implement-watchdog_hardlockup_probe.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: HAVE_NMI_WATCHDOG must implement watchdog_hardlockup_probe()
Date: Fri, 26 May 2023 18:41:32 -0700

Right now there is one arch (sparc64) that selects HAVE_NMI_WATCHDOG
without selecting HAVE_HARDLOCKUP_DETECTOR_ARCH.  Because of that one
architecture, we have some special case code in the watchdog core to
handle the fact that watchdog_hardlockup_probe() isn't implemented.

Let's implement watchdog_hardlockup_probe() for sparc64 and get rid of the
special case.

As a side effect of doing this, code inspection tells us that we could fix
a minor bug where the system won't properly realize that NMI watchdogs are
disabled.  Specifically, on powerpc if CONFIG_PPC_WATCHDOG is turned off
the arch might still select CONFIG_HAVE_HARDLOCKUP_DETECTOR_ARCH which
selects CONFIG_HAVE_NMI_WATCHDOG.  Since CONFIG_PPC_WATCHDOG was off then
nothing will override the "weak" watchdog_hardlockup_probe() and we'll
fallback to looking at CONFIG_HAVE_NMI_WATCHDOG.

Link: https://lkml.kernel.org/r/20230526184139.2.Ic6ebbf307ca0efe91f08ce2c1eb4a037ba6b0700@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Suggested-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/Kconfig            |    3 ++-
 arch/sparc/kernel/nmi.c |    5 +++++
 kernel/watchdog.c       |   13 -------------
 3 files changed, 7 insertions(+), 14 deletions(-)

--- a/arch/Kconfig~watchdog-hardlockup-have_nmi_watchdog-must-implement-watchdog_hardlockup_probe
+++ a/arch/Kconfig
@@ -405,7 +405,8 @@ config HAVE_NMI_WATCHDOG
 	bool
 	help
 	  The arch provides a low level NMI watchdog. It provides
-	  asm/nmi.h, and defines its own arch_touch_nmi_watchdog().
+	  asm/nmi.h, and defines its own watchdog_hardlockup_probe() and
+	  arch_touch_nmi_watchdog().
 
 config HAVE_HARDLOCKUP_DETECTOR_ARCH
 	bool
--- a/arch/sparc/kernel/nmi.c~watchdog-hardlockup-have_nmi_watchdog-must-implement-watchdog_hardlockup_probe
+++ a/arch/sparc/kernel/nmi.c
@@ -65,6 +65,11 @@ void arch_touch_nmi_watchdog(void)
 }
 EXPORT_SYMBOL(arch_touch_nmi_watchdog);
 
+int __init watchdog_hardlockup_probe(void)
+{
+	return 0;
+}
+
 static void die_nmi(const char *str, struct pt_regs *regs, int do_panic)
 {
 	int this_cpu = smp_processor_id();
--- a/kernel/watchdog.c~watchdog-hardlockup-have_nmi_watchdog-must-implement-watchdog_hardlockup_probe
+++ a/kernel/watchdog.c
@@ -217,19 +217,6 @@ void __weak watchdog_hardlockup_disable(
  */
 int __weak __init watchdog_hardlockup_probe(void)
 {
-	/*
-	 * If CONFIG_HAVE_NMI_WATCHDOG is defined then an architecture
-	 * is assumed to have the hard watchdog available and we return 0.
-	 */
-	if (IS_ENABLED(CONFIG_HAVE_NMI_WATCHDOG))
-		return 0;
-
-	/*
-	 * Hardlockup detectors other than those using CONFIG_HAVE_NMI_WATCHDOG
-	 * are required to implement a non-weak version of this probe function
-	 * to tell whether they are available. If they don't override then
-	 * we'll return -ENODEV.
-	 */
 	return -ENODEV;
 }
 
_

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
arm64-enable-perf-events-based-hard-lockup-detector-fix.patch
watchdog-hardlockup-keep-kernelnmi_watchdog-sysctl-as-0444-if-probe-fails.patch
watchdog-hardlockup-have_nmi_watchdog-must-implement-watchdog_hardlockup_probe.patch
watchdog-hardlockup-dont-use-raw_cpu_ptr-in-watchdog_hardlockup_kick.patch
watchdog-hardlockup-in-watchdog_hardlockup_check-use-cpumask_copy.patch
watchdog-hardlockup-remove-softlockup-comment-in-touch_nmi_watchdog.patch
watchdog-buddy-cleanup-how-watchdog_buddy_check_hardlockup-is-called.patch
watchdog-buddy-dont-copy-the-cpumask-in-watchdog_next_cpu.patch
watchdog-buddy-simplify-the-dependency-for-hardlockup_detector_prefer_buddy.patch
watchdog-hardlockup-move-smp-barriers-from-common-code-to-buddy-code.patch
watchdog-hardlockup-rename-have_hardlockup_detector_non_arch-to-_perf_or_buddy.patch