Re: [PATCH] USB host: Fix lockdep warning in AMD PLL quirk

[Roedel, Joerg]

On Wed, Apr 06, 2011 at 11:16:07AM -0400, Alan Stern wrote:
> On Wed, 6 Apr 2011, Joerg Roedel wrote:

> The counter really should be a bool: Has the chipset already been
> probed or not?  After all, nobody cares how many times this routine was 
> called.
> 
> > +	spin_unlock_irqrestore(&amd_lock, flags);
> 
> This code now contains a bug: You incremented the probe_count _before_
> doing the probe.  If another thread calls this routine right now, it
> will get an incorrect result.
> 
> Fixing this up should be fairly easy.

Hmm, we can get rid of the amd_lock completly if every thread uses the
following call-order:

	usb_amd_find_chipset_info();
	usb_amd_quirk_pll_enable();
	usb_amd_quirk_pll_disable();
	usb_amd_dev_put();

In that case we can just change the probe_count and isoc_reqs into
atomic_t with some care and should be fine, no?
Problem is that I don't know if the above call-order is guaranteed.

	Joerg

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