On 2010-10-22 05:34, Ted Ts'o wrote: > On Thu, Oct 21, 2010 at 07:46:15PM +0200, Jens Axboe wrote: >> By the sound of things, if I were you I'd turn on the mem and slab >> debugging to catch use-before-init and use-after-free. Mysterious hangs >> in the IO sub system are usually caused by such bugs. And the regular >> debugging aids, just to see if that produces anything of interest. > > It looks like it was a use-after-free bug in my code. I'm running a > full set of set of tests now, but so far, it's gotten a lot further > than it went before, so I think I've figured it out. > > I'm not sure why it caused the weird behaviour that it did (I got as > far as figuring out that somehow we lost the unplug timer, so after > the queue got plugged it never got unplugged), but I'm not going to > ask too many questions. :-) > > Maybe later on I'll try to figure out if there's any way to add some > kind of sanity checking so that screw ups in in the bio code's caller > cause a clearer failure (such as a BUG_ON), but that'll have to wait > for when I have some free time. In my experience, use-after-free bugs are best caught using the allocator poisoning along with lock checking. I guess that didn't trigger for you? Out of curiousity, what was the exact bug? -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
