On Fri, May 25, 2012 at 10:34:47AM +0800, Asias He wrote: > 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 <[email protected]> > Cc: "Michael S. Tsirkin" <[email protected]> > Cc: [email protected] > Cc: [email protected] > Signed-off-by: Asias He <[email protected]>
Acked-by: Michael S. Tsirkin <[email protected]> > --- > drivers/block/virtio_blk.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c > index 693187d..1bed517 100644 > --- a/drivers/block/virtio_blk.c > +++ b/drivers/block/virtio_blk.c > @@ -584,13 +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); > while ((vbr = virtqueue_detach_unused_buf(vblk->vq))) { > -- > 1.7.10.2 _______________________________________________ Virtualization mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/virtualization
