linux-kernel - Re: function call fw_iso_resource_mange(..) (core-iso.c) does not return

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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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