On Thu, 2018-04-19 at 12:24 -0700, Omar Sandoval wrote: > We quiesce and freeze the queue before tearing it down, so it won't be > NULL while we're still doing I/O. Cc'ing Bart in case I'm lying to you, > though ;) blk_cleanup_queue() waits until all I/O requests have finished. Since the block layer tracing code is triggered from inside the code that processes a request it is safe to access the request pointer from inside the tracing code. But I think the question was about the parent of the request queue kobj instead of about the request queue pointer, the device structure that is embedded in struct gendisk? I think that parent can disappear at any time. Most block drivers call del_gendisk() before they call blk_cleanup_queue(). Unless I'm overlooking something I think the request queue will need to obtain a reference to the gendisk device from inside blk_register_queue() and drop that reference from inside blk_cleanup_queue() to make it safe for the tracing code to access struct gendisk. Bart.
