linux-kernel - Re: 2.6.29.4: hibernation fails with large kernel trace

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Message-ID: <20090528114527.GA2140@elf.ucw.cz>
Date:	Thu, 28 May 2009 13:45:27 +0200
From:	Pavel Machek <pavel@....cz>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	akpm@...ux-foundation.org, niel.lambrechts@...il.com,
	linux-kernel@...r.kernel.org, gregkh@...e.de, rjw@...k.pl
Subject: Re: 2.6.29.4: hibernation fails with large kernel trace

Hi!

> > The process "fuser" is stuck down in the fuse code awaiting a response
> > or something.  I'd suspect that this is the cause of the freezing
> > failure:
> 
> Yup, the 'gvfs-fuse-daemon' process is already in the refrigerator, so
> it cannot complete the request from the 'fuser' process.
> 
> The solution is simple, really: just allow the 'fuser' task to freeze
> despite the fact that it's inside a syscall.  There's the small detail
> of actually implementing this, without breaking everything else...
> 
> What complicates the above is that we need to enable freezing not just
> inside fuse callbacks, but in the VFS as well.  E.g. sys_rename()
> sleeping on i_mutex needs to be freezable as well, otherwise another
> thread that is already frozen and holding that i_mutex will block that
> rename.
> 
> So,
> 
> a) we need some sort of mechanism to selectively disable freezing only
>    for those syscalls which might (directly) touch hardware state.  It
>    _hopefully_ should be enough to do so with read, write and ioctl,
> 
> b) we need to re-enable freezing for these in fuse.
> 
> That's the theory.  I promised a prototype some time ago but haven't
> yet got around to doing it.

In the meantime, people should stop/restart fuse around
suspend/hibernation, I guess...
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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