Re: [I810_AUDIO] 1/x: Fix wait queue race in drain_dac

[Herbert Xu]

On Mon, Jan 12, 2004 at 04:48:19PM -0500, Jeff Garzik wrote:
> 
> hmmm, I'll have to think on this one a bit.  You are described observed 
> behavior here... can you go a bit deeper, and describe what two code 
> paths are racing?  I think I might a _different_ race in the code we're 
> looking at, but I do not yet see the race you are describing :(

A				B
drain_dac()
	count > 0
				i810_channel_interrupt()
					i810_update_ptr()
						count = 0
						wake_up()
	set_current_state()
	schedule_timeout()
	*TIMEOUT*

> >schedule() already checks for signals.
> 
> Well -- A signal won't be pending until after you call 
> schedule_timeout() ;-)  A signal, particularly SIGINT, might even occur 
> _during_ the schedule_timeout().

Yes, but as long as you check signal_pending at least once in each
loop it does the right thing.  Can you point me to a scenario where
checking it right after schedule_timeout produces different behaviour
than the current code?

Cheers,
-- 
Debian GNU/Linux 3.0 is out! ( http://www.debian.org/ )
Email:  Herbert Xu ~{PmV>HI~} <herbert@xxxxxxxxxxxxxxxxxxx>
Home Page: http://gondor.apana.org.au/~herbert/
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