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 B63C078B4E; Sun, 28 Jul 2024 00:48:21 +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=1722127701; cv=none; b=g0tLufvYbIAL9CWpAfoZQYJ9b4DZfSzcMCMIF46PWQCMjaLsB/qI5wUE2p8tXDVJfwhKfs6ElT1nZOXhIVKxmtmT9hLw1GRM64oJLpa48exucbgpuDy2eK6hNxVhJgdg5y9+996XaxfPxzdvXDq1qERtFe4W+uS513RSbXf14TE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722127701; c=relaxed/simple; bh=suNuq5w0lt7MlowI5jGay92gxTN4o7N4ohzkpssq1v0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=rgVVw8CnwsMwS8v6epmDGzR4Xr+1CE5wJr1tLY/zWfR/OhK7YoTGI+6augfkQPwA8RqEI7yanymeFSSEGtHkrMY/uSAuTPHbRU6wTqV1rRvSQ86Z7Ugd8YfgsX/j940XKyXTZ2/x9sMej7QjlqYtZmPsQ8iVfjFmZxHJ5QtJjBI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Cshcsmb1; 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="Cshcsmb1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6D027C4AF09; Sun, 28 Jul 2024 00:48:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1722127701; bh=suNuq5w0lt7MlowI5jGay92gxTN4o7N4ohzkpssq1v0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Cshcsmb1ObvHjG/COQ3zQYuwAM84Lp+s1gJRt3FCoetfzpQxJnXmiad16pvwo6T98 otEN9snYWJ1U+iEKNxNJNRRs6msfobyEyMLQyz4LizBYVoE6f0O2NbaOdK1+GDJQu2 6t72sOo8T+6TH/6kQ7lOI48DWLt8Aa2e/eW9WKyHe0wiT3133CVi2cbfRYosCL3Pxg C/dfHevYva2loRnWWrTsbPImrjOpbTfdLow5nULwzH8iVfVeHB0IcD55xLEbsPDeTq dUC1u7V9NQY9PoeXeaCcNWOqQQ0OIdiVjgiZp6/pi9RlrDu4w6H+47d3x1cNj8E1KN 63pO2TeouqR/g== 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 6.6 4/9] rcutorture: Fix rcu_torture_fwd_cb_cr() data race Date: Sat, 27 Jul 2024 20:48:05 -0400 Message-ID: <20240728004812.1701139-4-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240728004812.1701139-1-sashal@kernel.org> References: <20240728004812.1701139-1-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 6.6.43 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 781146600aa49..46612fb15fc6d 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -2592,7 +2592,7 @@ 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