From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 318C04EB85D; Thu, 17 Sep 2026 15:36:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789659420; cv=none; b=RKNDYqw4HujTGo2MTKnXGtsjgKGa42zwOi1Q/k+UBdSBfI9ztcNbs2wvPSzK3AoVuc4Wb9XTVilMS6eUTPHqrgnwK+grjt8JR7CV/XXw7vx02TxH5PQWImhgOd+/jkJhg6Znl+rVIldvj3xSLvuMNyc27oxzQnM3520q2fLBgXE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789659420; c=relaxed/simple; bh=v6syUgfWjK8d3AxnZ0w+wdf6kyNQGfgIO8qgjVZDupI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=KuLEUTdKdrG2hnEeeLJiq222OjVO+haCl3hJXLiI8TIf2sSdAooguSJwsU3taRMfbXpa7H8YlnhK3/3RaL2eIUUAlurCkdwTvBE5hJLcn5aKy1kidxwUSmIo7+ZuD0knSQvxGdMSssDmlfTtoN0ixTvqlD4qGy/zlBymu6IDqrY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=d3NpnzVF; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="d3NpnzVF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4D0ED1F000FF; Thu, 17 Sep 2026 15:36:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789659415; bh=is0zmsU3YV6NxPMtQZ7fMuC/Blj0bAxbtKOUZuzeN5A=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=d3NpnzVFeL6321NBamjEaR3lmV9nG21O+K6l+2MBKG3qDgIpVPKCR3ELD+Gehb7i4 1rCO6DCvMy6nR+Jyz8scnxHk2VBbTPqoSwx0eBnzrmro+EjL/wmK8Pje7t51IrladH JsGvMWkTAWkTeliDY6laffbBEc36HqtVyuhih6ws= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Allison Henderson , Jakub Kicinski , Sasha Levin Subject: [PATCH 7.2 210/733] net/rds: clear cp_flags bits individually in rds_conn_path_reset() Date: Thu, 17 Sep 2026 16:08:38 +0100 Message-ID: <20260917151356.417095966@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260917151350.597953846@linuxfoundation.org> References: <20260917151350.597953846@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Allison Henderson [ Upstream commit 103c4b13c4f50322910078d1c02f29334a574122 ] rds_conn_path_reset() wipes the whole flag word with a plain cp->cp_flags = 0 store. Every other accessor of that word uses atomic bitops, and some of them can run concurrently with the reset: RDS_LL_SEND_FULL is set from rds_send_xmit() and cleared from the transport completion paths, neither of which holds anything that excludes the shutdown worker. A plain store racing an atomic read-modify-write on the same word is a data race, and whichever side loses has its update silently discarded. Clear the two bits the reset is actually responsible for instead. RDS_IN_XMIT and RDS_RECV_REFILL need no store at all here: they belong to the caller, rds_conn_shutdown(), which waits for both to be clear before calling the transport shutdown and this reset. This also gives every bit in cp_flags a single well-defined writer discipline, which the following patches rely on when they turn RDS_IN_XMIT and RDS_RECV_REFILL into bit locks held across the teardown: a blanket store mid-teardown would destroy lock ownership that an atomic clear preserves. Oracle UEK carries the same conversion ("net/rds: Preserve essential connection state flags"), motivated by its asynchronous shutdown state machine, whose progress and destroy flags must survive the reset. UEK's variant also clears RDS_IN_XMIT and RDS_RECV_REFILL because there the reset runs as the final step of a teardown that owns both bits, making those clears its unlock. Upstream that release belongs in rds_conn_shutdown(): once a later patch in this series turns the two bits into locks held across the teardown, ending ownership needs release semantics and a wake-up that a plain clear inside the reset would not provide. Based on Oracle UEK commit "net/rds: Preserve essential connection state flags" by Gerd Rausch. Fixes: 00e0f34c6166 ("RDS: Connection handling") Signed-off-by: Allison Henderson Link: https://patch.msgid.link/20260828223921.202913-4-achender@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/rds/connection.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/net/rds/connection.c b/net/rds/connection.c index 7c8ab8e973e1b..46ac72088f842 100644 --- a/net/rds/connection.c +++ b/net/rds/connection.c @@ -120,7 +120,15 @@ static void rds_conn_path_reset(struct rds_conn_path *cp) rds_stats_inc(s_conn_reset); rds_send_path_reset(cp); - cp->cp_flags = 0; + + /* Clear the bits the reset is responsible for individually: a + * blanket cp_flags = 0 is a plain store that can clobber a + * concurrent atomic read-modify-write on the same word. + * RDS_IN_XMIT and RDS_RECV_REFILL belong to the caller, + * rds_conn_shutdown(), and are left alone here. + */ + clear_bit(RDS_LL_SEND_FULL, &cp->cp_flags); + clear_bit(RDS_RECONNECT_PENDING, &cp->cp_flags); /* Do not clear next_rx_seq here, else we cannot distinguish * retransmitted packets from new packets, and will hand all -- 2.53.0