linux-kernel - Re: [PATCH] driver core: multithreaded probing

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Message-ID: <20070625081624.GB23847@kroah.com>
Date:	Mon, 25 Jun 2007 01:16:24 -0700
From:	Greg KH <greg@...ah.com>
To:	"Huang, Ying" <ying.huang@...el.com>
Cc:	Stefan Richter <stefanr@...6.in-berlin.de>,
	Cornelia Huck <cornelia.huck@...ibm.com>,
	Adrian Bunk <bunk@...sta.de>, david@...g.hm,
	David Miller <davem@...emloft.net>,
	"bunk@...sta.de; Duncan Sands" <duncan.sands@...h.u-psud.fr>,
	Phillip Susi <psusi@....rr.com>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] driver core: multithreaded probing - more
	parallelismcontrol

On Sun, Jun 24, 2007 at 11:04:13PM +0800, Huang, Ying wrote:
> >From: Greg KH [mailto:greg@...ah.com]
> >I'm still not convinced that we need to add this kind of complexity to
> >the driver core, instead of just letting the individual driver
> >subsystems do this, if they want to do it.
> 
> It may appear not necessary that providing more multithreaded device
> probing in the driver core, but it seems more necessary that providing
> more parallel control in the driver core to make some device probing
> more single-threaded.
> 
> There does exist multithreaded device probing in current driver core
> implementation, supposing two devices are hot-plugged at the same time.

No, that is a bus-specific thing, and no bus that I know of supports
that at this time.

> But, many device drivers are written without this taken into account.

That's why no bus does this :)

> I think it may be better to make default device probing process more
> single-threaded in the driver core. The single-thread workqueue or some
> customized version of workqueue like that implemented by my patch can be
> used for this. The parallel control mechanism can be used to implement
> multithreaded device probing in needed subsystems too.

But remember, the individual busses already do this all in a single
thread anyway, nothing is needed in the driver core to do this.

thanks,

greg k-h
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