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[103.168.172.201]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6e87b086e3esm10756866d6.31.2025.02.25.08.08.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 25 Feb 2025 08:08:55 -0800 (PST) Received: from phl-compute-06.internal (phl-compute-06.phl.internal [10.202.2.46]) by mailfauth.phl.internal (Postfix) with ESMTP id DA84B1200066; Tue, 25 Feb 2025 11:08:54 -0500 (EST) Received: from phl-mailfrontend-02 ([10.202.2.163]) by phl-compute-06.internal (MEProxy); Tue, 25 Feb 2025 11:08:54 -0500 X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeefvddrtddtgdekvddugecutefuodetggdotefrod ftvfcurfhrohhfihhlvgemucfhrghsthforghilhdpggftfghnshhusghstghrihgsvgdp uffrtefokffrpgfnqfghnecuuegrihhlohhuthemuceftddtnecusecvtfgvtghiphhivg hnthhsucdlqddutddtmdenucfjughrpeffhffvvefukfhfgggtuggjsehttdertddttddv necuhfhrohhmpeeuohhquhhnucfhvghnghcuoegsohhquhhnrdhfvghnghesghhmrghilh drtghomheqnecuggftrfgrthhtvghrnhephedugfduffffteeutddvheeuveelvdfhleel ieevtdeguefhgeeuveeiudffiedvnecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrg hmpehmrghilhhfrhhomhepsghoqhhunhdomhgvshhmthhprghuthhhphgvrhhsohhnrghl ihhthidqieelvdeghedtieegqddujeejkeehheehvddqsghoqhhunhdrfhgvnhhgpeepgh hmrghilhdrtghomhesfhhigihmvgdrnhgrmhgvpdhnsggprhgtphhtthhopeefpdhmohgu vgepshhmthhpohhuthdprhgtphhtthhopehprghulhhmtghksehkvghrnhgvlhdrohhrgh dprhgtphhtthhopehrtghusehvghgvrhdrkhgvrhhnvghlrdhorhhgpdhrtghpthhtohep sghoqhhunhesfhhigihmvgdrnhgrmhgv X-ME-Proxy: Feedback-ID: iad51458e:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Tue, 25 Feb 2025 11:08:54 -0500 (EST) Date: Tue, 25 Feb 2025 08:08:53 -0800 From: Boqun Feng To: "Paul E. McKenney" Cc: rcu@vger.kernel.org Subject: Re: Testing of shared RCU branching Message-ID: References: Precedence: bulk X-Mailing-List: rcu@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: On Tue, Feb 25, 2025 at 07:58:01AM -0800, Paul E. McKenney wrote: > Hello, Boqun, > > I have run overnight tests on your earlier branches here: > > ccb986e8b69f ("MAINTAINERS: Update Joel's email address") > > These passed other than a KCSAN complaint involving > rcu_preempt_deferred_qs_handler() and rcu_read_unlock_special(). > This looks like the plain C-language writes to ->defer_qs_iw_pending. > > My guess is that this is low probability, despite having happened twice, > and that it happens when rcu_read_unlock_special() is interrupted, > resulting in rcu_preempt_deferred_qs_handler() being invoked as an > IRQ-work handler. Keeping in mind that RCU runs KCSAN so as to locate > data races between task and handler on the same CPU. > > Thoughts? > Do you have a KCSAN of this? Also this is not a regression, right? Meaning you probably have seen this before? Anyway, it should be an easy fix (just using READ_ONCE() and WRITE_ONCE()). I can send the fix out and put it in. Regards, Boqun > Thanx, Paul