From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qk1-f181.google.com (mail-qk1-f181.google.com [209.85.222.181]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C50031898E9 for ; Tue, 25 Feb 2025 16:11:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.222.181 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740499876; cv=none; b=Hv7geD+23nYiOjKMW0e8mrIooNv3NZIAenMcLe3zVtemszrcCcHIy/KoZVJgvdaylxaHd87L+442Mt9EjpBANzvhr5IoWK71YNSrwWjvt6y+FVA70g+O33GUvc3KowBEPku6EaW8aM9b8FOu4i+bCfLfmRbiCuWyL/6h4EzfXRU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740499876; c=relaxed/simple; bh=b+g9TWpP+/BL8lGvFhasPKnV+EYw8HGPOaolrDXVsXw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Ci9dGi5umEYzBBdg3rIeB/H9ScVI7cazxEGZI53v4aX9UvrBae77cbfoELuja5pWi7L4+0tuyh1+pkKm1HDP3p+wFNE7c/p7DuZYEh6CU4/+8YdEKtel6PpiS5YsDuuk4esRZz+e24f3+dSttoT1Qb99AuSeE/KVaWVPz8hMFx4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=k3dXwAKa; arc=none smtp.client-ip=209.85.222.181 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="k3dXwAKa" Received: by mail-qk1-f181.google.com with SMTP id af79cd13be357-7c0ade6036aso655684485a.0 for ; Tue, 25 Feb 2025 08:11:14 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1740499873; x=1741104673; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:feedback-id:from:to:cc:subject:date :message-id:reply-to; bh=fDJCZB9Pp6uRzDdb8U10QpXTANbtNp6AMax/hSuxDnA=; b=k3dXwAKaAK2FTSX61jtTxg1pty2aedOOulk0YSf6VaWB1Ld4c0BnK5WlHnEYhK7CHB /PhGWpQWSYd8q2C1weV3ROmRJXalLfD8UEgSf036Pjx6Dl7oizNavfx2IoHrg0nkEYz6 vx+vDDDjRrMlu68DEi8lEX2M6zLeM5e0gKrg/YhobREQzkH8naDborgoSSo80G3Mubnz 53zBvCQpiKyLnEAqP/KyMWd9/6RXYHOr2UY1caOxos3/WXEF6tJxyJSTPG49fpMcqQ9S r0y9FUndb78h5hkdavGgY2T4Sz4MRKQZRA9egiIq3vj1pVc6xBsZaS81GGHJbCH8sNOo tDsg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1740499873; x=1741104673; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:feedback-id:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=fDJCZB9Pp6uRzDdb8U10QpXTANbtNp6AMax/hSuxDnA=; b=ggumyU95+kZAESt1feimjiHaLEdjn421eLVZ8coqBXnux7yQtoxRALUB/9UZNIQaX1 U4D8Qv4jXTgPDooFDG2vGcsr1Lon9kJNhpy3HUgpM6Tky+N3gKgRPu278tIn+MNGGYRD +cZ3OP2gXJYw9HKOvl2uyTiPMZUvfCHVyWJW/mqNvHM9iki3qlkLMqR92oaLysX+n2QQ EgeUPHPTA6bWSsUd0OgEaRZ8+VIXDJm/2gRTQZX2fq0OHKi8YC3GFtJLF1TkIYaEHCpA HjcTgmAYznBmrf5bpZvxpa5QeY4IxlJ8bqWFMAJkoD7Fq1GWr/JwmjjrMktNnkyC00cG c2rA== X-Gm-Message-State: AOJu0YyXuEwYwnY4rS5fWuDihWZUXuOk0sWeADhcuG7yk9ObA60NC1MJ oqQZDO7zkeejrx0E2JwEEMVeJkkfACJbgkJyd+Zp1bjfvrTtxJZQ X-Gm-Gg: ASbGnctx/qKEW53QG2ds9EZzJcUbIH4QN0sRi1Cv5XrZWqY/4Ua1GcNWjnrYfhGssqY 1h/rSc9vfNNQCaa6MloSxd4ALgVpXlVD3xD60Td1D4AmLEqfi/oswP0MI9hkFNuSR71TR1S5oWF gOjwZDIrfeCm9QTaO5+I68XN2hbVGXfA+SEBFeF5rAnOQ/EQCuSqKsSb8haGDr3fzuxZocjlP25 XXeMiLrw3EJMi/3kM4zVP8GNSX/Me2g1Bv6k1KGkkWukx7gn6JOZiWFemu3T0BHZOp9lOVN+xls 5aSr8LoSfkVJf4zUvkFPv+4CVuaf87jYcsTsUHYr5EoOlBraS2VerwWZxkXxpMC2xPrCdXSUxKC tWkTyIm3l3VquF+tS X-Google-Smtp-Source: AGHT+IHIvgOxeF2vUrO6Id0susj4j+TlWdZrBA0+HuMl87x8rkL1oJM+QIYfbc8AAQIVSHuTbVfHAQ== X-Received: by 2002:a05:620a:31a4:b0:7c0:ac03:91be with SMTP id af79cd13be357-7c0c21ad273mr3041271285a.15.1740499873531; Tue, 25 Feb 2025 08:11:13 -0800 (PST) Received: from fauth-a2-smtp.messagingengine.com (fauth-a2-smtp.messagingengine.com. [103.168.172.201]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7c23c2992d5sm122754385a.10.2025.02.25.08.11.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 25 Feb 2025 08:11:13 -0800 (PST) Received: from phl-compute-08.internal (phl-compute-08.phl.internal [10.202.2.48]) by mailfauth.phl.internal (Postfix) with ESMTP id EFC9A1200068; Tue, 25 Feb 2025 11:11:12 -0500 (EST) Received: from phl-mailfrontend-02 ([10.202.2.163]) by phl-compute-08.internal (MEProxy); Tue, 25 Feb 2025 11:11:12 -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 11:11:12 -0500 (EST) Date: Tue, 25 Feb 2025 08:11:11 -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 08:08:53AM -0800, Boqun Feng wrote: > 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") > > Oh and I should have let you know, I updated next and dev branch, the latest ones are: next.2025.02.24a and dev.2025.02.24a in rcu repo. Regards, Boqun > > 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