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

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Message-Id: <200707052220.00555.rjw@sisk.pl>
Date:	Thu, 5 Jul 2007 22:19:59 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	oliver@...kum.org, pavel@....cz, paulus@...ba.org,
	stern@...land.harvard.edu, johannes@...solutions.net,
	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	mjg59@...f.ucam.org, benh@...nel.crashing.org
Subject: Re: [linux-pm] Re: [PATCH] Remove process freezer from suspend to RAM pathway

On Thursday, 5 July 2007 21:44, Miklos Szeredi wrote:
> > Am Donnerstag, 5. Juli 2007 schrieb Miklos Szeredi:
> > > > > Actually fuse allows SIGKILL, because it's always fatal, and the
> > > > > syscall may not be restarted.
> > > > 
> > > > I think you want to stick try_to_freeze() at the same places where you
> > > > do SIGKILL handling. That should solve the 'syslogd is unfreezeable'
> > > > problem.
> > > 
> > > I could, but it would not solve the general problem.  Namely, that the
> > > presence of fuse imposes a certain ordering in which userspace tasks
> > > have to be frozen.  And it is not possible to know this ordering.
> > 
> > Actually, why do you need this? There is no absolute need that you
> > finish the request. You must either finish the request or let yourself
> > be frozen.
> > 
> > A quick look through fuse reveals principally request_wait_answer()
> > And maybe a few other places. Is there some hidden reason you cannot
> > handle being frozen here?
> 
> Yes, fuse could handle being frozen there.  However that would only
> solve part of the problem: an operation waiting for a reply could be
> holding a VFS mutex and some other task may be blocked on that mutex.
> 
> How would you solve freezing those tasks?

How probable is this situation?

Greetings,
Rafael


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