From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932492AbdLGRSI (ORCPT ); Thu, 7 Dec 2017 12:18:08 -0500 Received: from fldsmtpe03.verizon.com ([140.108.26.142]:23066 "EHLO fldsmtpe03.verizon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756247AbdLGPwS (ORCPT ); Thu, 7 Dec 2017 10:52:18 -0500 From: alexander.levin@verizon.com Cc: Mike Christie , Nicholas Bellinger , alexander.levin@verizon.com X-Host: pioneer.tdc.vzwcorp.com To: "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" Subject: [PATCH AUTOSEL for 4.9 082/156] target: fix race during implicit transition work flushes Thread-Topic: [PATCH AUTOSEL for 4.9 082/156] target: fix race during implicit transition work flushes Thread-Index: AQHTb3Lvkpcfo5M+fk6ydwLmL/avVg== Date: Thu, 7 Dec 2017 15:49:15 +0000 Message-ID: <20171207154845.4814-82-alexander.levin@verizon.com> References: <20171207154845.4814-1-alexander.levin@verizon.com> In-Reply-To: <20171207154845.4814-1-alexander.levin@verizon.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-messagesentrepresentingtype: 1 x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.144.60.250] Content-Type: text/plain; charset="iso-8859-1" MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by nfs id vB7HIDEO026098 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 --- drivers/target/target_core_alua.c | 10 +--------- 1 file changed, 1 insertion(+), 9 deletions(-) diff --git a/drivers/target/target_core_alua.c b/drivers/target/target_core_alua.c index dc06f723133e..ee5b29aed54b 100644 --- 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 -- 2.11.0