Re: [linux-pm] Re: [PATCH] Remove process freezer from suspend to RAM pathway

Rafael J. Wysocki
2007-07-04T10:19:13Z

On Wednesday, 4 July 2007 10:26, Miklos Szeredi wrote:
> > > That's weird, I never had a suspend problem due to a fuse mount,
> > > though I have them all the time. And I suspect, that even the sync()
> >
> > Well, I don't either, because we don't freeze processes on
> > powerbooks. But I have heard that other people have problems with
> > suspending with a fuse filesystem mounted. Maybe the difference is
> > whether or not the filesystem is writable?
> >
> > > thing that suspend does is not the real cause, because sync() actually
> > > does nothing in fuse filesystems.
> >
> > It's not the filesystem sync method, as I understand it, it's that if
> > there are dirty pages in the page cache for files on the fuse
> > filesystem,
>
> Currently fuse doesn't produce dirty pages. Normal writes are done
> synchronously, and writable mmap is not supported. So sync() should
> really be a no-op for fuse.
>
> > the system will initiate a write-out on them and wait for it to
> > finish. But if the fuse userspace is frozen, the write-out will
> > never complete.
>
> Maybe there is some other fs operation being done, possibly not
> directly, but by waiting for a kernel thread, that does that.

We're going to limit the freezing of kernel threads to the ones that explicitly
want to be frozen, so if that's the case, then I think it'll be fixed soon.

> It would be nice, if someone who can reproduce the deadlock could
> debug it.

Agreed.

> Does sysrq still work during suspend?

Yes, it should work.

Greetings,
Rafael

--
"Premature optimization is the root of all evil." - Donald Knuth