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

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Date:	Wed, 9 May 2007 02:55:32 -0700
From:	Greg KH <greg@...ah.com>
To:	David Miller <davem@...emloft.net>
Cc:	torvalds@...ux-foundation.org, cornelia.huck@...ibm.com,
	bunk@...sta.de, linux-kernel@...r.kernel.org
Subject: Re: Please revert 5adc55da4a7758021bcc374904b0f8b076508a11
	(PCI_MULTITHREAD_PROBE)

On Tue, May 08, 2007 at 02:41:54PM -0700, David Miller wrote:
> From: Linus Torvalds <torvalds@...ux-foundation.org>
> Date: Tue, 8 May 2007 13:01:21 -0700 (PDT)
> 
> > In fact, there is nothing wrong with having *both* a synchronous part, and 
> > an async part:
> > 
> > 	.probe = mydriver_setup,
> > 	.probe_async = mydriver_spin_up_and_probe_devices,
>  ...
> > Hmm? Would something like this work? I dunno, but it seems a hell of a lot 
> > safer and more capable than the aborted PCI multithreaded probing that was 
> > an "all or nothing" approach.
> 
> I definitely agree that we need a transitonary approach to this.
> 
> Although I kind of preferred the idea you mentioned where the
> device could launch the asynchronous probe and just return from
> the normal ->probe() immediately.

Yes, let this be a decision the individual PCI driver does, I don't want
to put this two-stage thing in the driver core, but any individual bus
can implement it if they really want to.

> This might get tricky if the callers do some kind of reference
> counting or other resource management based upon the ->probe()
> return value since it wouldn't know what happened to the
> launched asynchronous probe when it returns from ->probe().

As long as the ->probe() call returns that the driver has clamed the
device, and the ->remove() call can be handled properly while the driver
is off doing whatever it wants to in the initialization, the driver core
should work just fine, no changes needed.

thanks,

greg k-h
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