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 1318A1482E6; Sun, 28 Jul 2024 00:49:06 +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=1722127747; cv=none; b=T6pxC7/L0wSya3BYt8lnzSoSNmfkbLkY25qe7UxGarGBNA/KCB5sMnvt96LrFtAAlZ0Z7UTDFFdOPUlg8jougJIgJridvwL+6nsYSnsgkhRW6RQXLDCRgo2PKBLeMGwNejhq95n0WZ8vwRID75aKQKbkxQEjbLLEzElj6KpbBbc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722127747; c=relaxed/simple; bh=DQ3EGMYH3xEK71gRrN+2pTzCzyUMW+9aupaJNbPi4vM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=bfE4apUVe5kcqwg9VDJ1aVwRv06z5MTipHfumg6WV882YDj4r5f6JbvGEyxwQcE2HjLFplJ4A50tEcIT0LEiIIrmkn/i/Bu7sirTT4zTAiB4ehSmBBaxmwD89F04Y8eRe/Tg0WgBGViVL9ahpF3GOsk1/KUfvcm2GlizTn9XKQU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=loQTUp7I; 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="loQTUp7I" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C89E8C4AF07; Sun, 28 Jul 2024 00:49:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1722127746; bh=DQ3EGMYH3xEK71gRrN+2pTzCzyUMW+9aupaJNbPi4vM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=loQTUp7I6rRegQ8slmO+nABJ72fDmTDNcxBnR841Pf8fZvSNp5f4L8EiWSTwdk2cr qpO4egM1h+CjlQuOMcA2T74DSH+k4MctF4J0nZrp24AGWmmLrcboGCO6SO1aq6gnSV 5gn0ENZDXM/ccLg48niVjm8kyamJYj1y3L2QGSPTATbSmrqm5PZ+YMQUpWQe53n5Qr j51dQ540kndpkZIg8WRtB/PqYekbu435Pjh9Zsb5+/3zPYrklMSPyQZ3VK7z2Shx9Q NXmoY6Pe8+HUjxWx96DYvjzus0mNdEb8tOEKnukgNzU/eZpX8Q8pVXUYO1SS42HDRq CcvdSQSiHhlaQ== 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 5.10 2/6] rcutorture: Fix rcu_torture_fwd_cb_cr() data race Date: Sat, 27 Jul 2024 20:48:55 -0400 Message-ID: <20240728004901.1704470-2-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240728004901.1704470-1-sashal@kernel.org> References: <20240728004901.1704470-1-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 5.10.223 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 9f505688291e5..5c4bdbe76df04 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -1867,7 +1867,7 @@ 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