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Wed, 15 Jul 2026 01:50:12 -0700 (PDT) From: zhidao su (Xiaomi) To: K Prateek Nayak , John Stultz Cc: Peter Zijlstra , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] sched/proxy_exec: Break cyclic proxy chains by deactivating blocked tasks In-Reply-To: <05a66f9b-dc82-4ada-a074-afaa7628c089@amd.com> References: <1df0e505-add4-4b7d-8e09-bc52402da617@amd.com> <20260714152220.4046736-1-soolaugust@gmail.com> <178408304702.304643.2084630008424110320@gmail.com> <05a66f9b-dc82-4ada-a074-afaa7628c089@amd.com> Date: Wed, 15 Jul 2026 16:50:04 +0800 Message-ID: <178410540499.687883.18324181636573149517@gmail.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 > Btw, I realized you'll need to reset this marker on migration, else > there is a rare chance of a stale p->blocked_donor pick_seq from an old > pick CPU colliding with the pick_seq after migration. Good catch. I think v3 should clear the marker when we migrate the task, so the pick state is only meaningful for a single walk on a single CPU. That avoids stale state from an old CPU colliding with a later walk. > You can make this fit as per your v3 scheme. I’m leaning toward keeping this proxy-local instead of putting it in a generic CPU switch helper. > Ack! I think eventually, blocked_on becomes a struct with a lock_type > enum + void* pointer which allows for interpreting the pointer based > on the lock_type. Makes sense, and that’s another reason I’d keep the walk marker separate from the blocked_on / blocked_donor representation itself. > I agree p->blocked_donor has other uses with the extended series so it > is best to use a separate variable to track the seq_count if we go down > that route. Right, that was my thinking as well.