The patch titled
Subject: watchdog/hardlockup: move SMP barriers from common code to buddy code
has been added to the -mm mm-nonmm-unstable branch. Its filename is
watchdog-hardlockup-move-smp-barriers-from-common-code-to-buddy-code.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/watchdog-hardlockup-move-smp-barriers-from-common-code-to-buddy-code.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@xxxxxxxxxxxx>
Subject: watchdog/hardlockup: move SMP barriers from common code to buddy code
Date: Fri, 26 May 2023 18:41:39 -0700
It's been suggested that since the SMP barriers are only potentially
useful for the buddy hardlockup detector, not the perf hardlockup
detector, that the barriers belong in the buddy code. Let's move them and
add clearer comments about why they're needed.
Link: https://lkml.kernel.org/r/20230526184139.9.I5ab0a0eeb0bd52fb23f901d298c72fa5c396e22b@changeid
Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
Suggested-by: Petr Mladek <pmladek@xxxxxxxx>
Reviewed-by: Petr Mladek <pmladek@xxxxxxxx>
Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/watchdog.c | 6 ------
kernel/watchdog_buddy.c | 21 +++++++++++++++++++++
2 files changed, 21 insertions(+), 6 deletions(-)
--- a/kernel/watchdog_buddy.c~watchdog-hardlockup-move-smp-barriers-from-common-code-to-buddy-code
+++ a/kernel/watchdog_buddy.c
@@ -51,6 +51,13 @@ void watchdog_hardlockup_enable(unsigned
if (next_cpu < nr_cpu_ids)
watchdog_hardlockup_touch_cpu(next_cpu);
+ /*
+ * Makes sure that watchdog is touched on this CPU before
+ * other CPUs could see it in watchdog_cpus. The counter
+ * part is in watchdog_buddy_check_hardlockup().
+ */
+ smp_wmb();
+
cpumask_set_cpu(cpu, &watchdog_cpus);
}
@@ -68,6 +75,13 @@ void watchdog_hardlockup_disable(unsigne
if (next_cpu < nr_cpu_ids)
watchdog_hardlockup_touch_cpu(next_cpu);
+ /*
+ * Makes sure that watchdog is touched on the next CPU before
+ * this CPU disappear in watchdog_cpus. The counter part is in
+ * watchdog_buddy_check_hardlockup().
+ */
+ smp_wmb();
+
cpumask_clear_cpu(cpu, &watchdog_cpus);
}
@@ -88,5 +102,12 @@ void watchdog_buddy_check_hardlockup(int
if (next_cpu >= nr_cpu_ids)
return;
+ /*
+ * Make sure that the watchdog was touched on next CPU when
+ * watchdog_next_cpu() returned another one because of
+ * a change in watchdog_hardlockup_enable()/disable().
+ */
+ smp_rmb();
+
watchdog_hardlockup_check(next_cpu, NULL);
}
--- a/kernel/watchdog.c~watchdog-hardlockup-move-smp-barriers-from-common-code-to-buddy-code
+++ a/kernel/watchdog.c
@@ -109,9 +109,6 @@ EXPORT_SYMBOL(arch_touch_nmi_watchdog);
void watchdog_hardlockup_touch_cpu(unsigned int cpu)
{
per_cpu(watchdog_hardlockup_touched, cpu) = true;
-
- /* Match with smp_rmb() in watchdog_hardlockup_check() */
- smp_wmb();
}
static bool is_hardlockup(unsigned int cpu)
@@ -141,9 +138,6 @@ static void watchdog_hardlockup_kick(voi
void watchdog_hardlockup_check(unsigned int cpu, struct pt_regs *regs)
{
- /* Match with smp_wmb() in watchdog_hardlockup_touch_cpu() */
- smp_rmb();
-
if (per_cpu(watchdog_hardlockup_touched, cpu)) {
per_cpu(watchdog_hardlockup_touched, cpu) = false;
return;
_
Patches currently in -mm which might be from dianders@xxxxxxxxxxxx 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
