From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759005Ab3KIHg5 (ORCPT ); Sat, 9 Nov 2013 02:36:57 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:32907 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757590Ab3KIGuY (ORCPT ); Sat, 9 Nov 2013 01:50:24 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Aaron Lu , James Bottomley Subject: [PATCH 3.10 24/74] SCSI: sd: call blk_pm_runtime_init before add_disk Date: Fri, 8 Nov 2013 22:51:29 -0800 Message-Id: <20131109065115.235241192@linuxfoundation.org> X-Mailer: git-send-email 1.8.5.rc0.dirty In-Reply-To: <20131109065113.502217951@linuxfoundation.org> References: <20131109065113.502217951@linuxfoundation.org> User-Agent: quilt/0.60-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Aaron Lu commit 10c580e4239df5c3344ca00322eca86ab2de880b upstream. Sujit has found a race condition that would make q->nr_pending unbalanced, it occurs as Sujit explained: " sd_probe_async() -> add_disk() -> disk_add_event() -> schedule(disk_events_workfn) sd_revalidate_disk() blk_pm_runtime_init() return; Let's say the disk_events_workfn() calls sd_check_events() which tries to send test_unit_ready() and because of sd_revalidate_disk() trying to send another commands the test_unit_ready() might be re-queued as the tagged command queuing is disabled. So the race condition is - Thread 1 | Thread 2 sd_revalidate_disk() | sd_check_events() ...nr_pending = 0 as q->dev = NULL| scsi_queue_insert() blk_runtime_pm_init() | blk_pm_requeue_request() -> | nr_pending = -1 since | q->dev != NULL " The problem is, the test_unit_ready request doesn't get counted the first time it is queued, so the later decrement of q->nr_pending in blk_pm_requeue_request makes it unbalanced. Fix this by calling blk_pm_runtime_init before add_disk so that all requests initiated there will all be counted. Signed-off-by: Aaron Lu Reported-and-tested-by: Sujit Reddy Thumma Signed-off-by: James Bottomley Signed-off-by: Greg Kroah-Hartman --- drivers/scsi/sd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/scsi/sd.c +++ b/drivers/scsi/sd.c @@ -2843,6 +2843,7 @@ static void sd_probe_async(void *data, a gd->events |= DISK_EVENT_MEDIA_CHANGE; } + blk_pm_runtime_init(sdp->request_queue, dev); add_disk(gd); if (sdkp->capacity) sd_dif_config_host(sdkp); @@ -2851,7 +2852,6 @@ static void sd_probe_async(void *data, a sd_printk(KERN_NOTICE, sdkp, "Attached SCSI %sdisk\n", sdp->removable ? "removable " : ""); - blk_pm_runtime_init(sdp->request_queue, dev); scsi_autopm_put_device(sdp); put_device(&sdkp->dev); }