[SCSI] Stop accepting SCSI requests before removing a device

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 <bvanassche@acm.org>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 8af6a64..b583277 100644 (file)
--- 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 9aa578a..d19d7e9 100644 (file)
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -967,13 +967,20 @@ 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);
 }