From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0C49814535A; Sun, 28 Jul 2024 00:48:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722127734; cv=none; b=Xx37dpt/ISFF8RsRFT3+lrnnJylrKjx9B6w+PcXOlEVsTZZylkxerbzKsE7wxMB51OIOFdfj93Z7K8wT/1VUbTl3bN3gDZRcCMRfs7M2fQJnv3AWf7FfMZQmDIRLg5EKZEBg8VIyUbO+7C+vIOiJZyakj+o5Asy3PwIuJLhdJoU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722127734; c=relaxed/simple; bh=7fN9jg+/l4OO5UkJTs3sgHOIzQ1RQVJB3UDHsdzEKos=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=iVJ6tiB6IoiKiL35eR/OnlBYywv+btOLtEdKJvltxMwGGWPGnEfbTjZePJoM/GQJyz9N0SlXfUihP1iNkJ3jEZdxg7RTriMAf3OwHic9AoUk2zDBEyoj4FDVazsaShQSdaw4G4zIsTQSDVEbsjalCxDei7EfFzzoZkbPzL/NAOg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mYW2Oh1k; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="mYW2Oh1k" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1828CC32781; Sun, 28 Jul 2024 00:48:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1722127733; bh=7fN9jg+/l4OO5UkJTs3sgHOIzQ1RQVJB3UDHsdzEKos=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mYW2Oh1kQezyYizXtbeGm8+CDg0Ny7aCX4O9KTd1E/cSVU1TxDopNhnKAnRZzTqS9 pvmpX6TplHBq98oxjvpttGpzW4Djq//z5T750F6aF2Sy7t15A4ohUyhNxqX0SIhjM/ jqy8xtDxyUZ9+HhzBLW5wddDkEPFKiSSneiZMEuvnbOHWJkyq/d7/BZnYyD0kNn3rp tKwt8HLIm0YBbItmotVLj/n7WZQqTuPaYB/SvKW3FOUFtco9CB/jwgAmWzkpedRXfG Z4T18JOjvqVX5RXunKcRbu4RDl90UaVNN46qo+K0uxFRpboHvssJQgQYUksaKVtz6L S+xBnxQ79Qebg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "Paul E. McKenney" , Marco Elver , Andrey Konovalov , kasan-dev@googlegroups.com, Sasha Levin , dave@stgolabs.net, josh@joshtriplett.org, frederic@kernel.org, neeraj.upadhyay@kernel.org, joel@joelfernandes.org, boqun.feng@gmail.com, urezki@gmail.com, rcu@vger.kernel.org Subject: [PATCH AUTOSEL 5.15 2/6] rcutorture: Fix rcu_torture_fwd_cb_cr() data race Date: Sat, 27 Jul 2024 20:48:43 -0400 Message-ID: <20240728004848.1703616-2-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240728004848.1703616-1-sashal@kernel.org> References: <20240728004848.1703616-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 5.15.164 Content-Transfer-Encoding: 8bit From: "Paul E. McKenney" [ Upstream commit 6040072f4774a575fa67b912efe7722874be337b ] On powerpc systems, spinlock acquisition does not order prior stores against later loads. This means that this statement: rfcp->rfc_next = NULL; Can be reordered to follow this statement: WRITE_ONCE(*rfcpp, rfcp); Which is then a data race with rcu_torture_fwd_prog_cr(), specifically, this statement: rfcpn = READ_ONCE(rfcp->rfc_next) KCSAN located this data race, which represents a real failure on powerpc. Signed-off-by: Paul E. McKenney Acked-by: Marco Elver Cc: Andrey Konovalov Cc: Signed-off-by: Sasha Levin --- kernel/rcu/rcutorture.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 9d8d1f233d7bd..a3bab6af4028f 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -2186,7 +2186,7 @@ static void rcu_torture_fwd_cb_cr(struct rcu_head *rhp) spin_lock_irqsave(&rfp->rcu_fwd_lock, flags); rfcpp = rfp->rcu_fwd_cb_tail; rfp->rcu_fwd_cb_tail = &rfcp->rfc_next; - WRITE_ONCE(*rfcpp, rfcp); + smp_store_release(rfcpp, rfcp); WRITE_ONCE(rfp->n_launders_cb, rfp->n_launders_cb + 1); i = ((jiffies - rfp->rcu_fwd_startat) / (HZ / FWD_CBS_HIST_DIV)); if (i >= ARRAY_SIZE(rfp->n_launders_hist)) -- 2.43.0