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Date: Tue, 4 Jun 2002 14:14:40 -0700 (PDT)
From: Julian Elischer <julian@elischer.org>
To: John Baldwin <jhb@FreeBSD.org>
Cc: Perforce Change Reviews <perforce@freebsd.org>
Subject: Re: PERFORCE change 12362 for review
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On Tue, 4 Jun 2002, John Baldwin wrote:

> http://people.freebsd.org/~peter/p4db/chv.cgi?CH=12362
> 
> Change 12362 by jhb@jhb_laptop on 2002/06/04 10:45:42
> 
> 	- Add a thread_runnable() macro to make some code more readable
> 	  and make the KSE diff easier.
> 	- Fix the adaptive mutex spin optimization.  We need to stop
> 	  spinning not just when mtx_owner(m) changes, but also if the
> 	  owner stops running.
> 
> Affected files ...
> 
> ... //depot/projects/smpng/sys/kern/kern_mutex.c#36 edit
> 
> Differences ...
> 
> ==== //depot/projects/smpng/sys/kern/kern_mutex.c#36 (text+ko) ====
> 
> @@ -70,6 +70,9 @@
>  #define mtx_owner(m)	(mtx_unowned((m)) ? NULL \
>  	: (struct thread *)((m)->mtx_lock & MTX_FLAGMASK))
>  
> +#define	thread_runnable(td)						\
> +	((td)->td_kse != NULL && (td)->td_kse->ke_oncpu != NOCPU)
> +    

this actually checks for "thread_running" not "thread_runnable".
Since you are mentioning KSE diffs, in KSE this test is performed by:

if (td->td_state == TDS_RUNNING)

and if you want to check for both running and runnable, you need:

if ((td->td_state == TDS_RUNNING) || (td->td_state == TDS_RUNQ))


>  /*
>   * Lock classes for sleep and spin mutexes.
>   */
> @@ -129,7 +132,7 @@
>  		 * If lock holder is actually running, just bump priority.
>  		 */
>  		 /* XXXKSE this test is not sufficient */
> -		if (td->td_kse && (td->td_kse->ke_oncpu != NOCPU)) { 
> +		if (thread_runnable(td)) {
>  			MPASS(td->td_proc->p_stat == SRUN
>  			|| td->td_proc->p_stat == SZOMB
>  			|| td->td_proc->p_stat == SSTOP);
> @@ -531,10 +534,10 @@
>  		 * CPU, spin instead of blocking.
>  		 */
>  		owner = (struct thread *)(v & MTX_FLAGMASK);
> -		if (m != &Giant && owner->td_kse != NULL &&
> -		    owner->td_kse->ke_oncpu != NOCPU) {
> +		if (m != &Giant && thread_runnable(owner)) {
>  			mtx_unlock_spin(&sched_lock);
> -			while (mtx_owner(m) == owner) {
> +			while (mtx_owner(m) == owner &&
> +			    thread_runnable(owner)) {
>  #ifdef __i386__
>  				ia32_pause();
>  #endif
> 


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