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Thu, 04 May 2023 19:35:54 -0700 (PDT) Received: from localhost ([203.59.190.92]) by smtp.gmail.com with ESMTPSA id g18-20020a62e312000000b0062dd9a8c1b8sm407591pfh.100.2023.05.04.19.35.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 04 May 2023 19:35:53 -0700 (PDT) Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Fri, 05 May 2023 12:35:39 +1000 Message-Id: Subject: Re: [PATCH v4 13/17] watchdog/hardlockup: detect hard lockups using secondary (buddy) CPUs From: "Nicholas Piggin" To: "Douglas Anderson" , "Petr Mladek" , "Andrew Morton" X-Mailer: aerc 0.14.0 References: <20230504221349.1535669-1-dianders@chromium.org> <20230504151100.v4.13.I6bf789d21d0c3d75d382e7e51a804a7a51315f2c@changeid> In-Reply-To: <20230504151100.v4.13.I6bf789d21d0c3d75d382e7e51a804a7a51315f2c@changeid> X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Ian Rogers , Randy Dunlap , Lecopzer Chen , kgdb-bugreport@lists.sourceforge.net, ricardo.neri@intel.com, Stephane Eranian , Guenter Roeck , sparclinux@vger.kernel.org, Will Deacon , Daniel Thompson , Andi Kleen , Chen-Yu Tsai , Matthias Kaehlcke , Catalin Marinas , Masayoshi Mizuma , ravi.v.shankar@intel.com, Tzung-Bi Shih , Colin Cross , Stephen Boyd , Pingfan Liu , linux-arm-kernel@lists.infradead.org, Sumit Garg , ito-yuichi@fujitsu.com, linux-perf-users@vger.kernel.org, Marc Zyngier , linuxppc-dev@lists.ozlabs.org, davem@davemloft.net Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Fri May 5, 2023 at 8:13 AM AEST, Douglas Anderson wrote: > From: Colin Cross > > Implement a hardlockup detector that doesn't doesn't need any extra > arch-specific support code to detect lockups. Instead of using > something arch-specific we will use the buddy system, where each CPU > watches out for another one. Specifically, each CPU will use its > softlockup hrtimer to check that the next CPU is processing hrtimer > interrupts by verifying that a counter is increasing. Powerpc's watchdog has an SMP checker, did you see it? It's all to all rather than buddy which makes it more complicated but arguably bit better functionality. Thanks, Nick