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

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Message-Id: <200707041226.34799.rjw@sisk.pl>
Date:	Wed, 4 Jul 2007 12:26:33 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	paulus@...ba.org, 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

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
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