Re: [PATCH RESEND v9 2/3] fuse: add optional kernel-enforced timeout for requests

[Sergey Senozhatsky <senozhatsky@chromium.org>]

On (24/12/04 09:51), Brian Geffon wrote:
> > > > >>
> > > > >> In those cases 1 minute fuse timeout will overshot HUNG_TASK_TIMEOUT
> > > > >> and then the question is whether HUNG_TASK_PANIC is set.
> 
> In my opinion this is a good argument for having the hung task timeout
> and a fuse timeout independent. The hung task timeout is for hung
> kernel threads

Sorry, but no, it's not only for kernel threads.

> in this situation we're potentially taking too long in
> userspace but that doesn't necessarily mean the system is hung.

And it's not for hung system.  It's for tasks that stuck unreasonably
long waiting for a particular event or resource.  And those tasks very
well can be user-space processes, being stuck in syscall waiting for
something.

> I think a loop which does an interruptible wait with a timeout of 1/2
> the hung task timeout would make sense to ensure the hung task timeout
> doesn't hit.

The point here is not to silent watchdog, we might as well just disable
it and call it a day.  The point here is that fuse can be used (and IS
in our particular case) as a network filesystem, and the problem can be
way outside of your system, so spinning in a wait loop doesn't fix any
problem on that remote system no matter how long we spin, and that's
what watchdog signals us.