del_gendisk() might not return due to failing to remove the /sys/block/vda/serial sysfs entry when another thread (udev) is trying to read it. virtblk_remove() vdev->config->reset() : guest will not kick us through interrupt del_gendisk() device_del() kobject_del(): got stuck, sysfs entry ref count non zero sysfs_open_file(): user space process read /sys/block/vda/serial sysfs_get_active() : got sysfs entry ref count dev_attr_show() virtblk_serial_show() blk_execute_rq() : got stuck, interrupt is disabled request cannot be finished This patch fixes it by calling del_gendisk() before we disable guest's interrupt so that the request sent in virtblk_serial_show() will be finished and del_gendisk() will success. This fixes another race in hot-unplug process. It is save to call del_gendisk(vblk->disk) before flush_work(&vblk->config_work) which might access vblk->disk, because vblk->disk is not freed until put_disk(vblk->disk). Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx> Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx> Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx Cc: kvm@xxxxxxxxxxxxxxx Signed-off-by: Asias He <asias@xxxxxxxxxx> --- drivers/block/virtio_blk.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index 693187d..7d5f5b0 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -584,12 +584,13 @@ static void __devexit virtblk_remove(struct virtio_device *vdev) vblk->config_enable = false; mutex_unlock(&vblk->config_lock); + del_gendisk(vblk->disk); + /* Stop all the virtqueues. */ vdev->config->reset(vdev); flush_work(&vblk->config_work); - del_gendisk(vblk->disk); /* Abort requests dispatched to driver. */ spin_lock_irqsave(&vblk->lock, flags); -- 1.7.10.1 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html