* + watchdog-perf-more-properly-prevent-false-positives-with-turbo-modes.patch added to mm-nonmm-unstable branch
@ 2023-05-19 21:28 Andrew Morton
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From: Andrew Morton @ 2023-05-19 21:28 UTC (permalink / raw
To: mm-commits, will, wens, tzungbi, swboyd, sumit.garg, ricardo.neri,
rdunlap, ravi.v.shankar, pmladek, npiggin, msys.mizuma, mpe, mka,
maz, mark.rutland, lecopzer.chen, kernelfans, irogers, groeck,
eranian, davem, daniel.thompson, christophe.leroy, ccross,
catalin.marinas, ak, dianders, akpm
The patch titled
Subject: watchdog/perf: more properly prevent false positives with turbo modes
has been added to the -mm mm-nonmm-unstable branch. Its filename is
watchdog-perf-more-properly-prevent-false-positives-with-turbo-modes.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/watchdog-perf-more-properly-prevent-false-positives-with-turbo-modes.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/perf: more properly prevent false positives with turbo modes
Date: Fri, 19 May 2023 10:18:26 -0700
Currently, in the watchdog_overflow_callback() we first check to see if
the watchdog had been touched and _then_ we handle the workaround for
turbo mode. This order should be reversed.
Specifically, "touching" the hardlockup detector's watchdog should avoid
lockups being detected for one period that should be roughly the same
regardless of whether we're running turbo or not. That means that we
should do the extra accounting for turbo _before_ we look at (and clear)
the global indicating that we've been touched.
NOTE: this fix is made based on code inspection. I am not aware of any
reports where the old code would have generated false positives. That
being said, this order seems more correct and also makes it easier down
the line to share code with the "buddy" hardlockup detector.
Link: https://lkml.kernel.org/r/20230519101840.v5.2.I843b0d1de3e096ba111a179f3adb16d576bef5c7@changeid
Fixes: 7edaeb6841df ("kernel/watchdog: Prevent false positives with turbo modes")
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>
---
kernel/watchdog_hld.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
--- a/kernel/watchdog_hld.c~watchdog-perf-more-properly-prevent-false-positives-with-turbo-modes
+++ a/kernel/watchdog_hld.c
@@ -114,14 +114,14 @@ static void watchdog_overflow_callback(s
/* Ensure the watchdog never gets throttled */
event->hw.interrupts = 0;
+ if (!watchdog_check_timestamp())
+ return;
+
if (__this_cpu_read(watchdog_nmi_touch) == true) {
__this_cpu_write(watchdog_nmi_touch, false);
return;
}
- if (!watchdog_check_timestamp())
- return;
-
/* check for a hardlockup
* This is done by making sure our timer interrupt
* is incrementing. The timer interrupt should have
_
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
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2023-05-19 21:28 + watchdog-perf-more-properly-prevent-false-positives-with-turbo-modes.patch added to mm-nonmm-unstable branch Andrew Morton
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