From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bart Van Assche Subject: [PATCH 4/4] scsi: Stop accepting SCSI requests before removing a device Date: Mon, 25 Jun 2012 18:17:18 +0000 Message-ID: <4FE8AB2E.10400@acm.org> References: <4FE8A9FC.6040805@acm.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from relay04ant.iops.be ([212.53.5.219]:46036 "EHLO relay04ant.iops.be" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754093Ab2FYSRU (ORCPT ); Mon, 25 Jun 2012 14:17:20 -0400 In-Reply-To: <4FE8A9FC.6040805@acm.org> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: linux-scsi , James Bottomley , Mike Christie , Jens Axboe , Tejun Heo , Jun'ichi Nomura , Stefan Richter , Joe Lawrence Avoid that the code for requeueing SCSI requests triggers a crash by making sure that that code isn't scheduled anymore after a device has been removed. Also, source code inspection of __scsi_remove_device() revealed a race condition in this function: no new SCSI requests must be accepted for a SCSI device after device removal started. Signed-off-by: Bart Van Assche Reviewed-by: Mike Christie Cc: James Bottomley Cc: Jens Axboe Cc: Joe Lawrence Cc: Jun'ichi Nomura Cc: --- drivers/scsi/scsi_lib.c | 7 ++++--- drivers/scsi/scsi_sysfs.c | 11 +++++++++-- 2 files changed, 13 insertions(+), 5 deletions(-) diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index 082c1e5..fc2b9f4 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -155,13 +155,14 @@ static void __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, int unbusy) /* * Requeue this command. It will go before all other commands - * that are already in the queue. + * that are already in the queue. Schedule requeue work under + * lock such that the kblockd_schedule_work() call happens + * before blk_cleanup_queue() finishes. */ spin_lock_irqsave(q->queue_lock, flags); blk_requeue_request(q, cmd->request); - spin_unlock_irqrestore(q->queue_lock, flags); - kblockd_schedule_work(q, &device->requeue_work); + spin_unlock_irqrestore(q->queue_lock, flags); } /* diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c index 42c35ff..efffc92 100644 --- a/drivers/scsi/scsi_sysfs.c +++ b/drivers/scsi/scsi_sysfs.c @@ -966,13 +966,20 @@ void __scsi_remove_device(struct scsi_device *sdev) device_del(dev); } else put_device(&sdev->sdev_dev); + + /* + * Stop accepting new requests and wait until all queuecommand() and + * scsi_run_queue() invocations have finished before tearing down the + * device. + */ scsi_device_set_state(sdev, SDEV_DEL); + blk_cleanup_queue(sdev->request_queue); + cancel_work_sync(&sdev->requeue_work); + if (sdev->host->hostt->slave_destroy) sdev->host->hostt->slave_destroy(sdev); transport_destroy_device(dev); - /* Freeing the queue signals to block that we're done */ - blk_cleanup_queue(sdev->request_queue); put_device(dev); }