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From: John Baldwin <jhb@FreeBSD.org>
To: David Xu <davidxu@FreeBSD.org>
Date: Wed, 5 Jan 2005 17:47:18 -0500
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cc: Perforce Change Reviews <perforce@FreeBSD.org>
Subject: Re: PERFORCE change 68252 for review
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On Tuesday 04 January 2005 08:14 am, David Xu wrote:
> http://perforce.freebsd.org/chv.cgi?CH=68252
>
> Change 68252 by davidxu@davidxu_tiger on 2005/01/04 13:14:06
>
> 	insert "pause" instructor for  i386.
> 	style fix.

You can use 'cpu_spinwait()' for this to be MI.

> Affected files ...
>
> ..
> //depot/projects/davidxu_thread/src/lib/libthread/thread/thr_pspinlock.c#7
> edit
>
> Differences ...
>
> ====
> //depot/projects/davidxu_thread/src/lib/libthread/thread/thr_pspinlock.c#7
> (text+ko) ====
>
> @@ -100,6 +100,10 @@
>  	else {
>  		count = SPIN_COUNT;
>  		while ((ret = umtx_trylock(&lck->s_lock, self->tid)) != 0) {
> +#ifdef __i386__
> +			/* tell cpu we are spinning */
> +			__asm __volatile("pause");
> +#endif
>  			if (--count <= 0) {
>  				count = SPIN_COUNT;
>  				_pthread_yield();
> @@ -120,7 +124,7 @@
>  	if (lock == NULL || (lck = *lock) == NULL)
>  		ret = EINVAL;
>  	else {
> -		ret =umtx_unlock(&lck->s_lock, self->tid);
> +		ret = umtx_unlock(&lck->s_lock, self->tid);
>  	}
>  	return (ret);
>  }

-- 
John Baldwin <jhb@FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org