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[103.168.172.200]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6e8976cccb0sm74171366d6.71.2025.03.04.19.05.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 04 Mar 2025 19:05:33 -0800 (PST) Received: from phl-compute-01.internal (phl-compute-01.phl.internal [10.202.2.41]) by mailfauth.phl.internal (Postfix) with ESMTP id 61039120006A; Tue, 4 Mar 2025 22:05:32 -0500 (EST) Received: from phl-mailfrontend-01 ([10.202.2.162]) by phl-compute-01.internal (MEProxy); Tue, 04 Mar 2025 22:05:32 -0500 X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeefvddrtddtgddutdefjedvucetufdoteggodetrf dotffvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdggtfgfnhhsuhgsshgtrhhisggv pdfurfetoffkrfgpnffqhgenuceurghilhhouhhtmecufedttdenucesvcftvggtihhpih gvnhhtshculddquddttddmnecujfgurhephffvvefufffkofgjfhgggfestdekredtredt tdenucfhrhhomhepuehoqhhunhcuhfgvnhhguceosghoqhhunhdrfhgvnhhgsehgmhgrih hlrdgtohhmqeenucggtffrrghtthgvrhhnpefghfffvefhhfdvgfejgfekvdelgfekgeev ueehlefhiedvgeffjefgteeugfehieenucffohhmrghinhepkhgvrhhnvghlrdhorhhgne cuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehmrghilhhfrhhomhepsghoqhhu nhdomhgvshhmthhprghuthhhphgvrhhsohhnrghlihhthidqieelvdeghedtieegqdduje ejkeehheehvddqsghoqhhunhdrfhgvnhhgpeepghhmrghilhdrtghomhesfhhigihmvgdr nhgrmhgvpdhnsggprhgtphhtthhopeefledpmhhouggvpehsmhhtphhouhhtpdhrtghpth htoheprhgtuhesvhhgvghrrdhkvghrnhgvlhdrohhrghdprhgtphhtthhopehpmhhlrggu vghksehsuhhsvgdrtghomhdprhgtphhtthhopehrohhsthgvughtsehgohhoughmihhsrd horhhgpdhrtghpthhtohepjhhohhhnrdhoghhnvghssheslhhinhhuthhrohhnihigrdgu vgdprhgtphhtthhopehsvghnohiihhgrthhskhihsegthhhrohhmihhumhdrohhrghdprh gtphhtthhopehprghulhhmtghksehkvghrnhgvlhdrohhrghdprhgtphhtthhopehfrhgv uggvrhhitgeskhgvrhhnvghlrdhorhhgpdhrtghpthhtohepnhgvvghrrghjrdhuphgrug hhhigrhieskhgvrhhnvghlrdhorhhgpdhrtghpthhtohepjhhovghlsehjohgvlhhfvghr nhgrnhguvghsrdhorhhg X-ME-Proxy: Feedback-ID: iad51458e:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Tue, 4 Mar 2025 22:05:30 -0500 (EST) From: Boqun Feng To: rcu@vger.kernel.org Cc: Petr Mladek , Steven Rostedt , John Ogness , Sergey Senozhatsky , "Paul E. McKenney" , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Uladzislau Rezki , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Davidlohr Bueso , Shuah Khan , Sebastian Andrzej Siewior , Clark Williams , Masami Hiramatsu , Yuntao Wang , Andrew Morton , Rasmus Villemoes , Guo Weikang , KP Singh , Huang Shijie , Raul E Rangel , Joel Granados , Anna Schumaker , "Martin K. Petersen" , =?utf-8?q?Thomas_Wei?= =?utf-8?q?=C3=9Fschuh?= , zhangguopeng , Thomas Gleixner , "Neeraj Upadhyay (AMD)" , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-rt-devel@lists.linux.dev, Breno Leitao , Valentin Schneider Subject: [PATCH rcu 06/10] context_tracking: Make RCU watch ct_kernel_exit_state() warning Date: Tue, 4 Mar 2025 19:05:01 -0800 Message-ID: <20250305030505.94059-7-boqun.feng@gmail.com> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250305030505.94059-1-boqun.feng@gmail.com> References: <20250305030505.94059-1-boqun.feng@gmail.com> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: "Paul E. McKenney" The WARN_ON_ONCE() in ct_kernel_exit_state() follows the call to ct_state_inc(), which means that RCU is not watching this WARN_ON_ONCE(). This can (and does) result in extraneous lockdep warnings when this WARN_ON_ONCE() triggers. These extraneous warnings are the opposite of helpful. Therefore, invert the WARN_ON_ONCE() condition and move it before the call to ct_state_inc(). This does mean that the ct_state_inc() return value can no longer be used in the WARN_ON_ONCE() condition, so discard this return value and instead use a call to rcu_is_watching_curr_cpu(). This call is executed only in CONFIG_RCU_EQS_DEBUG=y kernels, so there is no added overhead in production use. [Boqun: Add the subsystem tag in the title] Reported-by: Breno Leitao Signed-off-by: Paul E. McKenney Reviewed-by: Valentin Schneider Reviewed-by: Frederic Weisbecker Link: https://lore.kernel.org/r/bd911cd9-1fe9-447c-85e0-ea811a1dc896@paulmck-laptop Signed-off-by: Boqun Feng --- kernel/context_tracking.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c index 938c48952d26..fb5be6e9b423 100644 --- a/kernel/context_tracking.c +++ b/kernel/context_tracking.c @@ -80,17 +80,16 @@ static __always_inline void rcu_task_trace_heavyweight_exit(void) */ static noinstr void ct_kernel_exit_state(int offset) { - int seq; - /* * CPUs seeing atomic_add_return() must see prior RCU read-side * critical sections, and we also must force ordering with the * next idle sojourn. */ rcu_task_trace_heavyweight_enter(); // Before CT state update! - seq = ct_state_inc(offset); - // RCU is no longer watching. Better be in extended quiescent state! - WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && (seq & CT_RCU_WATCHING)); + // RCU is still watching. Better not be in extended quiescent state! + WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !rcu_is_watching_curr_cpu()); + (void)ct_state_inc(offset); + // RCU is no longer watching. } /*