From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754086Ab1G0Ajc (ORCPT ); Tue, 26 Jul 2011 20:39:32 -0400 Received: from mga02.intel.com ([134.134.136.20]:18089 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753604Ab1G0AfM (ORCPT ); Tue, 26 Jul 2011 20:35:12 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.67,272,1309762800"; d="scan'208";a="32380349" From: Andi Kleen References: <20110726534.972201586@firstfloor.org> In-Reply-To: <20110726534.972201586@firstfloor.org> To: James.Bottomley@suse.de, gregkh@suse.de, ak@linux.intel.com, linux-kernel@vger.kernel.org, stable@kernel.org, tim.bird@am.sony.com, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH] [20/98] put stricter guards on queue dead checks Message-Id: <20110727003512.53DEF2403FF@tassilo.jf.intel.com> Date: Tue, 26 Jul 2011 17:35:12 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.35-longterm review patch. If anyone has any objections, please let me know. ------------------ From: James Bottomley commit 86cbfb5607d4b81b1a993ff689bbd2addd5d3a9b upstream. SCSI uses request_queue->queuedata == NULL as a signal that the queue is dying. We set this state in the sdev release function. However, this allows a small window where we release the last reference but haven't quite got to this stage yet and so something will try to take a reference in scsi_request_fn and oops. It's very rare, but we had a report here, so we're pushing this as a bug fix The actual fix is to set request_queue->queuedata to NULL in scsi_remove_device() before we drop the reference. This causes correct automatic rejects from scsi_request_fn as people who hold additional references try to submit work and prevents anything from getting a new reference to the sdev that way. Signed-off-by: James Bottomley Signed-off-by: Greg Kroah-Hartman Signed-off-by: Andi Kleen --- drivers/scsi/scsi_sysfs.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) Index: linux-2.6.35.y/drivers/scsi/scsi_sysfs.c =================================================================== --- linux-2.6.35.y.orig/drivers/scsi/scsi_sysfs.c +++ linux-2.6.35.y/drivers/scsi/scsi_sysfs.c @@ -319,14 +319,8 @@ static void scsi_device_dev_release_user kfree(evt); } - if (sdev->request_queue) { - sdev->request_queue->queuedata = NULL; - /* user context needed to free queue */ - scsi_free_queue(sdev->request_queue); - /* temporary expedient, try to catch use of queue lock - * after free of sdev */ - sdev->request_queue = NULL; - } + /* NULL queue means the device can't be used */ + sdev->request_queue = NULL; scsi_target_reap(scsi_target(sdev)); @@ -961,6 +955,12 @@ void __scsi_remove_device(struct scsi_de if (sdev->host->hostt->slave_destroy) sdev->host->hostt->slave_destroy(sdev); transport_destroy_device(dev); + + /* cause the request function to reject all I/O requests */ + sdev->request_queue->queuedata = NULL; + + /* Freeing the queue signals to block that we're done */ + scsi_free_queue(sdev->request_queue); put_device(dev); }