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[103.168.172.201]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7c573d8ab26sm280194985a.110.2025.03.14.10.37.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 14 Mar 2025 10:37:58 -0700 (PDT) Message-ID: <67d46976.050a0220.13a4aa.9cf4@mx.google.com> X-Google-Original-Message-ID: Received: from phl-compute-12.internal (phl-compute-12.phl.internal [10.202.2.52]) by mailfauth.phl.internal (Postfix) with ESMTP id 64B6D1200066; Fri, 14 Mar 2025 13:37:58 -0400 (EDT) Received: from phl-mailfrontend-01 ([10.202.2.162]) by phl-compute-12.internal (MEProxy); Fri, 14 Mar 2025 13:37:58 -0400 X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeefvddrtddtgddufedugeehucetufdoteggodetrf dotffvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdggtfgfnhhsuhgsshgtrhhisggv pdfurfetoffkrfgpnffqhgenuceurghilhhouhhtmecufedttdenucesvcftvggtihhpih gvnhhtshculddquddttddmnecujfgurhepfffhvfevuffkfhggtggujgesthdtredttddt vdenucfhrhhomhepuehoqhhunhcuhfgvnhhguceosghoqhhunhdrfhgvnhhgsehgmhgrih hlrdgtohhmqeenucggtffrrghtthgvrhhnpefhtedvgfdtueekvdekieetieetjeeihedv teehuddujedvkedtkeefgedvvdehtdenucffohhmrghinhepkhgvrhhnvghlrdhorhhgne cuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehmrghilhhfrhhomhepsghoqhhu nhdomhgvshhmthhprghuthhhphgvrhhsohhnrghlihhthidqieelvdeghedtieegqdduje ejkeehheehvddqsghoqhhunhdrfhgvnhhgpeepghhmrghilhdrtghomhesfhhigihmvgdr nhgrmhgvpdhnsggprhgtphhtthhopedukedpmhhouggvpehsmhhtphhouhhtpdhrtghpth htohepihhofihorhhkvghrtdesghhmrghilhdrtghomhdprhgtphhtthhopegrkhhpmhes lhhinhhugidqfhhouhhnuggrthhiohhnrdhorhhgpdhrtghpthhtohepfihilhhlsehkvg hrnhgvlhdrohhrghdprhgtphhtthhopehpvghtvghriiesihhnfhhrrgguvggrugdrohhr ghdprhgtphhtthhopehmihhnghhosehrvgguhhgrthdrtghomhdprhgtphhtthhopehloh hnghhmrghnsehrvgguhhgrthdrtghomhdprhgtphhtthhopehmhhhirhgrmhgrtheskhgv rhhnvghlrdhorhhgpdhrtghpthhtoheprghnnhgrrdhstghhuhhmrghkvghrsehorhgrtg hlvgdrtghomhdprhgtphhtthhopehjohgvlhdrghhrrghnrgguohhssehkvghrnhgvlhdr ohhrgh X-ME-Proxy: Feedback-ID: iad51458e:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Fri, 14 Mar 2025 13:37:57 -0400 (EDT) Date: Fri, 14 Mar 2025 10:37:54 -0700 From: Boqun Feng To: Lance Yang Cc: akpm@linux-foundation.org, will@kernel.org, peterz@infradead.org, mingo@redhat.com, longman@redhat.com, mhiramat@kernel.org, anna.schumaker@oracle.com, joel.granados@kernel.org, kent.overstreet@linux.dev, leonylgao@tencent.com, linux-kernel@vger.kernel.org, rostedt@goodmis.org, senozhatsky@chromium.org, tfiga@chromium.org, amaindex@outlook.com, John Stultz Subject: Re: [PATCH RESEND v2 0/3] hung_task: extend blocking task stacktrace dump to semaphore References: <20250314144300.32542-1-ioworker0@gmail.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: <20250314144300.32542-1-ioworker0@gmail.com> Hi Lance, On Fri, Mar 14, 2025 at 10:42:57PM +0800, Lance Yang wrote: > Hi all, > > Inspired by mutex blocker tracking[1], this patch series extend the > feature to not only dump the blocker task holding a mutex but also to > support semaphores. Unlike mutexes, semaphores lack explicit ownership > tracking, making it challenging to identify the root cause of hangs. To > address this, we introduce a last_holder field to the semaphore structure, > which is updated when a task successfully calls down() and cleared during > up(). > > The assumption is that if a task is blocked on a semaphore, the holders > must not have released it. While this does not guarantee that the last > holder is one of the current blockers, it likely provides a practical hint > for diagnosing semaphore-related stalls. > Could you copy John Stultz for the future versions? Because John is working on proxy execution, which will make a task always track which mutex it's blocked by: https://lore.kernel.org/lkml/20250312221147.1865364-3-jstultz@google.com/ I feel it's better to build the hung task detection with that in mind, thanks! Regards, Boqun [...]