On Mon, 2012-07-16 at 13:03 -0400, Steven Rostedt wrote: > On Mon, 2012-07-16 at 18:36 +0200, Mike Galbraith wrote: > > > > > > Ouch, you just turned the rt_read_lock() into a spin lock. If a higher > > > > priority process preempted a lower priority process that holds the same > > > > lock, it will deadlock. > > > > > > Hm, how, it's doing cpu_chill()? > > > > 'course PI is toast, so *poof*. Since just enabling the lockdep bits > > seems to fix it up, maybe that's the patchlet to submit (less is more). > > There's that too. But the issue I was talking about is with all trylock > loops. As holding an rt-mutex now disables migration, if a high priority > process preempts a task that holds the lock, and then the high prio task > starts spinning waiting for that lock to release, the lower priority > process will never get to run to release it. The cpu_chill() doesn't > help. Hrm. I better go make a testcase, this one definitely wants pounding through thick skull. I think all of the chilling in patchlet is really ugly anyway, so would prefer to trash it all, just enable the lockdep bits. If it turns out we really do need to bounce off of counts, go get a bigger hammer when the need arises. For the nonce, the pre-installed hammer _seemed_ big enough for the job. What's a good way to beat living hell out of btrfs? I've never been into destructive fs testing, since they usually lived on my one and only disk. x3550 has two, and OS clone has already been sacrificed. -Mike -- 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
