From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935362AbdLRQCh (ORCPT ); Mon, 18 Dec 2017 11:02:37 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:38588 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934797AbdLRQCc (ORCPT ); Mon, 18 Dec 2017 11:02:32 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Mike Christie , Nicholas Bellinger , Sasha Levin Subject: [PATCH 4.9 105/177] target: fix race during implicit transition work flushes Date: Mon, 18 Dec 2017 16:48:48 +0100 Message-Id: <20171218152915.392851329@linuxfoundation.org> X-Mailer: git-send-email 2.15.1 In-Reply-To: <20171218152909.823644066@linuxfoundation.org> References: <20171218152909.823644066@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mike Christie [ Upstream commit 760bf578edf8122f2503a3a6a3f4b0de3b6ce0bb ] This fixes the following races: 1. core_alua_do_transition_tg_pt could have read tg_pt_gp_alua_access_state and gone into this if chunk: if (!explicit && atomic_read(&tg_pt_gp->tg_pt_gp_alua_access_state) == ALUA_ACCESS_STATE_TRANSITION) { and then core_alua_do_transition_tg_pt_work could update the state. core_alua_do_transition_tg_pt would then only set tg_pt_gp_alua_pending_state and the tg_pt_gp_alua_access_state would not get updated with the second calls state. 2. core_alua_do_transition_tg_pt could be setting tg_pt_gp_transition_complete while the tg_pt_gp_transition_work is already completing. core_alua_do_transition_tg_pt then waits on the completion that will never be called. To handle these issues, we just call flush_work which will return when core_alua_do_transition_tg_pt_work has completed so there is no need to do the complete/wait. And, if core_alua_do_transition_tg_pt_work was running, instead of trying to sneak in the state change, we just schedule up another core_alua_do_transition_tg_pt_work call. Note that this does not handle a possible race where there are multiple threads call core_alua_do_transition_tg_pt at the same time. I think we need a mutex in target_tg_pt_gp_alua_access_state_store. Signed-off-by: Mike Christie Signed-off-by: Nicholas Bellinger Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/target/target_core_alua.c | 10 +--------- 1 file changed, 1 insertion(+), 9 deletions(-) --- a/drivers/target/target_core_alua.c +++ b/drivers/target/target_core_alua.c @@ -1073,16 +1073,8 @@ static int core_alua_do_transition_tg_pt /* * Flush any pending transitions */ - if (!explicit && atomic_read(&tg_pt_gp->tg_pt_gp_alua_access_state) == - ALUA_ACCESS_STATE_TRANSITION) { - /* Just in case */ - tg_pt_gp->tg_pt_gp_alua_pending_state = new_state; - tg_pt_gp->tg_pt_gp_transition_complete = &wait; + if (!explicit) flush_work(&tg_pt_gp->tg_pt_gp_transition_work); - wait_for_completion(&wait); - tg_pt_gp->tg_pt_gp_transition_complete = NULL; - return 0; - } /* * Save the old primary ALUA access state, and set the current state