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Message-ID: <d12dc75ae4092c04a3594cc8a5374927@gatzka.org>
Date: Wed, 22 May 2013 10:53:38 +0200
From: Stephan Gatzka <stephan.gatzka@...il.com>
To: Stefan Richter <stefanr@...6.in-berlin.de>
Cc: Peter Hurley <peter@...leysoftware.com>,
linux1394-devel@...ts.sourceforge.net, Tejun Heo <tj@...nel.org>,
linux-kernel@...r.kernel.org
Subject: Re: function call fw_iso_resource_mange(..) (core-iso.c) does not return
> I am a friend of the self-ID-complete worklet, for two reasons:
> - Even if there was no need for the TI TSB41BA3D workaround (e.g.
> even
> if we simply stopped supporting TSB41BA3D), it would still be
> worthwhile to have at least the self-ID-complete IRQ BH performed
> in
> a non-atomic context. We should try to move as much of the
> firewire-core self-ID-complete handler as possible out of the
> currently
> spinlock protected section in order make more of this stuff
> preemptible and replace a few GFP_ATOMIC slab allocations by
> GFP_NOFS
> ones. (Could be GFP_KERNEL in absence of firewire-sbp2.)
> I would have liked to work on this already long ago, but such is
> life.
> - How do you propose to access the PHY registers without sleeping?
> Or more to the point: How do you propose to mix sleeping and
> non-sleeping PHY register accesses? (Since we can't get rid of
> the sleeping ones.) If the accesses are not fully serialized, you
> will
> get corrupt PHY reg reads or writes. If they are fully serialized,
> the
> non-sleeping PHY reg accesses need to go a try-lock route and will
> be
> forced to error out during periods when a sleeping PHY reg access
> goes
> on, without even the ability to reschedule if it is done in a
> tasklet
> context.
I totally agree.
Stephan
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