From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932295Ab2L1TjG (ORCPT ); Fri, 28 Dec 2012 14:39:06 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:55387 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932209Ab2L1TSr (ORCPT ); Fri, 28 Dec 2012 14:18:47 -0500 Message-Id: <20121228190348.832174310@decadent.org.uk> User-Agent: quilt/0.60-1 Date: Fri, 28 Dec 2012 20:04:59 +0100 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, David Jeffery , Chad Dupuis , Saurav Kashyap , James Bottomley Subject: [ 089/173] [SCSI] qla2xxx: Test and clear FCPORT_UPDATE_NEEDED atomically. In-Reply-To: <20121228190330.025298996@decadent.org.uk> X-SA-Exim-Connect-IP: 151.217.219.220 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: David Jeffery commit a394aac88506159e047630fc90dc2242568382d8 upstream. When the qla2xxx driver loses access to multiple, remote ports, there is a race condition which can occur which will keep the request stuck on a scsi request queue indefinitely. This bad state occurred do to a race condition with how the FCPORT_UPDATE_NEEDED bit is set in qla2x00_schedule_rport_del(), and how it is cleared in qla2x00_do_dpc(). The problem port has its drport pointer set, but it has never been processed by the driver to inform the fc transport that the port has been lost. qla2x00_schedule_rport_del() sets drport, and then sets the FCPORT_UPDATE_NEEDED bit. In qla2x00_do_dpc(), the port lists are walked and any drport pointer is handled and the fc transport informed of the port loss, then the FCPORT_UPDATE_NEEDED bit is cleared. This leaves a race where the dpc thread is processing one port removal, another port removal is marked with a call to qla2x00_schedule_rport_del(), and the dpc thread clears the bit for both removals, even though only the first removal was actually handled. Until another event occurs to set FCPORT_UPDATE_NEEDED, the later port removal is never finished and qla2xxx stays in a bad state which causes requests to become stuck on request queues. This patch updates the driver to test and clear FCPORT_UPDATE_NEEDED atomically. This ensures the port state changes are processed and not lost. Signed-off-by: David Jeffery Signed-off-by: Chad Dupuis Signed-off-by: Saurav Kashyap Signed-off-by: James Bottomley Signed-off-by: Ben Hutchings --- drivers/scsi/qla2xxx/qla_os.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/drivers/scsi/qla2xxx/qla_os.c +++ b/drivers/scsi/qla2xxx/qla_os.c @@ -3541,9 +3541,9 @@ qla2x00_do_dpc(void *data) "ISP abort end.\n"); } - if (test_bit(FCPORT_UPDATE_NEEDED, &base_vha->dpc_flags)) { + if (test_and_clear_bit(FCPORT_UPDATE_NEEDED, + &base_vha->dpc_flags)) { qla2x00_update_fcports(base_vha); - clear_bit(FCPORT_UPDATE_NEEDED, &base_vha->dpc_flags); } if (test_bit(ISP_QUIESCE_NEEDED, &base_vha->dpc_flags)) {