Hello, Asias. On Mon, May 28, 2012 at 10:15:18AM +0800, Asias He wrote: > >I don't think the patch description is correct. The lock switcihng is > >inherently broken and the patch doesn't really fix the problem > >although it *might* make the problem less likely. Trying to switch > >locks while there are other accessors of the lock is simply broken, it > >can never work without outer synchronization. > > Since the lock switching is broken, is it a good idea to force all > the drivers to use the block layer provided lock? i.e. Change the > API from > blk_init_queue(rfn, driver_lock) to blk_init_queue(rfn). Any reason > not to use the block layer provided one. I think hch tried to do that a while ago. Dunno what happened to the patches. IIRC, the whole external lock thing was about sharing a single lock across different request_queues. Not sure whether it's actually beneficial enough or just a crazy broken optimization. > >Your patch might make > >the problem somewhat less likely simply because queue draining makes a > >lot of request_queue users go away. > > Who will use the request_queue after blk_cleanup_queue()? Anyone who still holds a ref might try to issue a new request on a dead queue. ie. blkdev with filesystem mounted goes away and the FS issues a new read request after blk_cleanup_queue() finishes drainig. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
