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

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Message-Id: <E1I60CR-00066n-00@dorka.pomaz.szeredi.hu>
Date:	Wed, 04 Jul 2007 10:26:59 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	paulus@...ba.org
CC:	miklos@...redi.hu, oliver@...kum.org, benh@...nel.crashing.org,
	mjg59@...f.ucam.org, linux-pm@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [linux-pm] Re: [PATCH] Remove process freezer from suspend to RAM
	pathway

> > 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.

It would be nice, if someone who can reproduce the deadlock could
debug it.  Does sysrq still work during suspend?

Miklos
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