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Message-Id: <1183676393.3388.89.camel@localhost.localdomain>
Date: Fri, 06 Jul 2007 08:59:52 +1000
From: Benjamin Herrenschmidt <benh@...nel.crashing.org>
To: Alan Stern <stern@...land.harvard.edu>
Cc: Paul Mackerras <paulus@...ba.org>,
Johannes Berg <johannes@...solutions.net>,
"Rafael J. Wysocki" <rjw@...k.pl>,
Linux-pm mailing list <linux-pm@...ts.linux-foundation.org>,
Kernel development list <linux-kernel@...r.kernel.org>,
Pavel Machek <pavel@....cz>,
Matthew Garrett <mjg59@...f.ucam.org>
Subject: Re: [linux-pm] Re: [PATCH] Remove process freezer from suspend to
RAM pathway
On Thu, 2007-07-05 at 10:23 -0400, Alan Stern wrote:
>
> How will that help? Block the kernel thread in the freezer or block it
> in the driver -- either way it is blocked. So how do your deadlocks
> get resolved?
Because nobody is waiting on that kernel thread anyway without a freezer
so there is no deadlock anymore.
> I disagree with your analysis -- not that it's completely wrong, but it
> points out an existing basic problem in the kernel. The kernel should
> never depend on userspace! More correctly, a task executing in the
> kernel should never block with any sort of mutex or other lock held (in
> a way that would preclude it from being frozen, let's say) while
> waiting for a response from userspace.
>
> Then the dependency graph would be easy to construct: User tasks can
> depend on whatever they want, and kernel threads never depend on a user
> task.
In an idea world, there would be no hunger...
> If this contradicts the existing implementations and APIs for userspace
> filesystems, then so be it. My conclusion would be that the
> implementations and APIs should be changed.
Why are you guys working so hard and spending so much energy to try to
avoid doing the right thing is beyond my understanding...
> It _does_ apply to kernel threads. That's exactly why I wrote above
> that kernel threads which try to do I/O during a suspend will need
> extra attention.
Ok none at all if you don't have a freezer.
Ben.
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