On 08/07/12 08:53, Chanho Min wrote: > On Tue, Aug 7, 2012 at 2:56 AM, Bart Van Assche <bvanassche@xxxxxxx> wrote: >> Indeed. How about the patch below ? Scsi devices are removed from >> starved_list after blk_cleanup_queue() and before put_device(). That >> guarantees that inside scsi_run_queue() get_device() under host lock >> will succeed. > > Thanks, IMHO, it's harmless and the simple way to solve this issue. > But, I think the second half of your patches are not required, extra > referecne is might suffice? I'm afraid that without the second half of that patch the following race is still possible: - sdev reference count drops to zero while scsi_run_queue() is in progress and while that sdev is on the starved_list of its SCSI host; scsi_device_dev_release_usercontext() call is scheduled but not yet executed. - scsi_run_queue() takes that sdev off the local starved_list. - scsi_run_queue() calls get_device() and that call fails since the sdev reference count is zero. - scsi_device_dev_release_usercontext() gets scheduled and frees the sdev. - scsi_run_queue() proceeds and calls __blk_run_queue() on a freed queue, which is what we were trying to avoid. Bart. -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
