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 8783B2AD2A; Sun, 28 Jul 2024 00:47:55 +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=1722127675; cv=none; b=qoQT2xYmQIScHKgoVfc2YotsXCl/Ub3getMnTuqQWamqOExnFx8nshoZOuTOwpDa2HqZmadVU94EiBCA6nIO9AUgwm8FOXJrqq/YKrZkaRUTGqLbPEKVeJA9r5y5paPendnjEmznDNgDp7GZFD1kD0mCdtULbux5KbCbdOiBm2Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722127675; c=relaxed/simple; bh=E+DhjlNNB8Qj7eEnAJcRy7w7HwhyiNNalMkLKCAYfKU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ghy3JjO0GddvCZ6o/TpFZW+wL0SE/9WOfPOWtR3gvM+zegWxy0PYNGEm9ysiDpa7cJP1xUxMDRng0XShM6NYz05VFEF5/Pi15Sce9y9dhPL68Rl+XAqeI9+i0rsu+yWCgN+uGPVPZejRSgavyAxoV63qvmA+n5OEiJA3Yd5iOlg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DQTiZIev; 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="DQTiZIev" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6117AC4AF09; Sun, 28 Jul 2024 00:47:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1722127675; bh=E+DhjlNNB8Qj7eEnAJcRy7w7HwhyiNNalMkLKCAYfKU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DQTiZIevWp+VLsitn282IPI8860/C9+43gx9KnTGgwUs6wxuRcnctLWOVZMxK5zf0 W20m8nh+SIxUSkiJpfs0ir3rxgeQ/i8wxY4meyLhc76HNX+HZk9cTYbWgKT7nSsoXp X5RmIA234fHpDIUXI7QCfqbVWU2SLnGzhu14MHLtaCb7PLPsCJPP9YPwb23HOy+YGF 5yYHHTNOd4Hu3YwHkvQf0Gg1TDIKjNk8ww4tNp91YD9yabCu8rle7S79sBYovjdb3V nP7XKUtjwUbiHyYGqpp+NP79pJwfabZ13XQlbTDfkpekkWjHO+6JY3zSWjAJPgo0Ij rzz9vJ3Std6qQ== 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 6.10 07/16] rcutorture: Fix rcu_torture_fwd_cb_cr() data race Date: Sat, 27 Jul 2024 20:47:24 -0400 Message-ID: <20240728004739.1698541-7-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240728004739.1698541-1-sashal@kernel.org> References: <20240728004739.1698541-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.10.2 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 807fbf6123a77..251cead744603 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -2626,7 +2626,7 @@ 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