linux-kernel - Re: Please revert 5adc55da4a7758021bcc374904b0f8b076508a11 (PCI_MULTITHREAD

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Message-ID: <Pine.LNX.4.64.0705091050410.4467@asgard.lang.hm>
Date:	Wed, 9 May 2007 10:53:52 -0700 (PDT)
From:	david@...g.hm
To:	Cornelia Huck <cornelia.huck@...ibm.com>
cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Adrian Bunk <bunk@...sta.de>, Greg K-H <greg@...ah.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Duncan Sands <duncan.sands@...h.u-psud.fr>
Subject: Re: Please revert 5adc55da4a7758021bcc374904b0f8b076508a11
 (PCI_MULTITHREAD_PROBE)

On Wed, 9 May 2007, Cornelia Huck wrote:

> On Wed, 9 May 2007 10:09:33 -0700 (PDT),
> david@...g.hm wrote:
>
>>> Hm, so that sound like a case for a distinct setup() routine:
>>>
>>> 1. bus calls ->probe(), which return synchronously
>>> 2. bus calls ->probe_async() for all devices (optional)
>>> 3. bus waits for all probes to finish
>>> 4. bus calls ->setup() for all devices (which does the registering)
>>
>> this is exactly what I've been trying to describe.
>
> Nearly, but with a slightly different spin...
>
>>
>>> (->setup() can but need not be sync, although it should be for your
>>> case)
>>
>> if it's not sync then you have race conditions again
>
> ...but not all busses will care. If your bus wants to enforce ordering,
> it must enforce it to be sync. If your bus allows hotplug and calling
> setup() later on, it may also allow async. (setup() is a bit
> dual-purpose in this idea.)

if you want the registration to use hotplug and be async then do do the 
registration during step 2 and make step 4 be a noop, in fact some drivers 
may do all their work in step 2, while others (everything currently) will 
do all their work during step 1

David Lang


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