Re: 2.6.7-mm7

[Greg KH]

On Fri, Jul 09, 2004 at 01:00:45PM -0700, Andrew Morton wrote:
> Jesse Stockall <stockall@xxxxxxxx> wrote:
> >
> > On Fri, 2004-07-09 at 14:54, Andrew Morton wrote:
> >                        down_write_trylock(&usb_all_devices_rwsem));
> >  > 
> >  > That's a bit unusual.  Could you (or Alan) please explain the reason for
> >  > this a little more?
> > 
> >  I believe you want this thread
> > 
> >  http://marc.theaimsgroup.com/?l=linux-usb-devel&m=108923404032264&w=2
> 
> Oh, OK.  Recursively taking an rwsem for reading is certainly deadlocky. 
> The main reason for not supporting this is that heavy down_read() traffic
> can trivially livelock down_write() waiters.  Alan's patch will introduce
> that shortcoming.
> 
> Really, it would be better to get the locking sorted out.

I agree, and we will before submitting the code to Linus.

thanks,

greg k-h
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