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Mon, 23 Mar 2026 09:26:05 -0700 (PDT) Date: Mon, 23 Mar 2026 17:26:03 +0100 From: Petr Mladek To: mrungta@google.com Cc: Jinchao Wang , Yunhui Cui , Stephane Eranian , Ian Rogers , Li Huafei , Feng Tang , Max Kellermann , Jonathan Corbet , Douglas Anderson , Andrew Morton , Florian Delizy , Shuah Khan , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org Subject: Re: [PATCH v2 4/5] watchdog/hardlockup: improve buddy system detection timeliness Message-ID: References: <20260312-hardlockup-watchdog-fixes-v2-0-45bd8a0cc7ed@google.com> <20260312-hardlockup-watchdog-fixes-v2-4-45bd8a0cc7ed@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260312-hardlockup-watchdog-fixes-v2-4-45bd8a0cc7ed@google.com> On Thu 2026-03-12 16:22:05, Mayank Rungta via B4 Relay wrote: > From: Mayank Rungta > > Currently, the buddy system only performs checks every 3rd sample. With > a 4-second interval. If a check window is missed, the next check occurs > 12 seconds later, potentially delaying hard lockup detection for up to > 24 seconds. > > Modify the buddy system to perform checks at every interval (4s). > Introduce a missed-interrupt threshold to maintain the existing grace > period while reducing the detection window to 8-12 seconds. > > Best and worst case detection scenarios: > > Before (12s check window): > - Best case: Lockup occurs after first check but just before heartbeat > interval. Detected in ~8s (8s till next check). > - Worst case: Lockup occurs just after a check. > Detected in ~24s (missed check + 12s till next check + 12s logic). > > After (4s check window with threshold of 3): > - Best case: Lockup occurs just before a check. > Detected in ~8s (0s till 1st check + 4s till 2nd + 4s till 3rd). > - Worst case: Lockup occurs just after a check. > Detected in ~12s (4s till 1st check + 4s till 2nd + 4s till 3rd). > > Reviewed-by: Douglas Anderson > Signed-off-by: Mayank Rungta LGTM: Reviewed-by: Petr Mladek Best Regards, Petr