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Date: Thu, 16 Sep 2004 19:22:49 -0700
From: Nate Lawson <nate@root.org>
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To: John Baldwin <jhb@FreeBSD.org>
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cc: "M. Warner Losh" <imp@bsdimp.com>
Subject: Re: cvs commit: src/sys/dev/md md.c
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John Baldwin wrote:
> On Thursday 16 September 2004 08:59 pm, M. Warner Losh wrote:
> 
>>In message: <414A109E.4080601@samsco.org>
>>
>>            Scott Long <scottl@samsco.org> writes:
>>: Or just use a semaphore.
>>
>>Or a condition variable.
> 
> 
> That doesn't help, a condition variable doesn't have state like a semaphore.  
> The correct fix is to do this:
> 
> thread A
> ----------
> 	mtx_lock();
> 	adjust_state();
> 	mtx_unlock();
> 	wakeup();
> 
> thread B
> ---------
> 	mtx_lock();
> 	while (state_still_needs_sleep())
> 		msleep(...)
> 	mtx_unlock()
> 
> Proving that there is no race is left as an exercise to the reader. :)

Isn't this exactly what I said?

-Nate