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

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Date:	Thu, 5 Jul 2007 22:53:34 +0200
From:	Oliver Neukum <oliver@...kum.org>
To:	linux-pm@...ts.linux-foundation.org
Cc:	Miklos Szeredi <miklos@...redi.hu>, mjg59@...f.ucam.org,
	linux-kernel@...r.kernel.org, pavel@....cz,
	johannes@...solutions.net
Subject: Re: [linux-pm] Re: [PATCH] Remove process freezer from suspend to RAM pathway

Am Donnerstag, 5. Juli 2007 schrieb Oliver Neukum:
> Am Donnerstag, 5. Juli 2007 schrieb Miklos Szeredi:
> > > > 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?
> > > 
> > > OK, you made me reach for literatur on theoretical computer science.
> > > 
> > > IMHO the range of actions a fuse server is inherently limited.
> > > You must never ever block on a lock one of your clients is holding. In
> > > this case the limitation is not influenced by the freezer.
> > 
> > Obviously.  But I wasn't about the server trying to acquire a lock
> > held by a client.  I was talking about a client trying to acquire a
> > lock held by _another_ client.
> > 
> > If this coincides with the server (or some other task which the server
> > is depending on) being frozen before the clients, the freezer has a
> > problem.
> 
> True, but that case can only happen if servers are frozen before clients.
> You don't need a full dependency graph. A simple set sequence of two
> classes of tasks will do.

Any replying to myself. A deadlock here is not fatal. You can and will
timeout in the freezer and can try again.

	REegards
		Oliver

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