The following reply was made to PR kern/32287; it has been noted by GNATS.

From: YAMAMOTO Takashi <yamt@mwd.biglobe.ne.jp>
To: tech-kern@netbsd.org
Cc: gnats-bugs@netbsd.org, kern-bug-people@netbsd.org,
	gnats-admin@netbsd.org, netbsd-bugs@netbsd.org
Subject: Re: kern/32287: Processes hang in "mclpl"
Date: Thu, 15 Dec 2005 22:55:44 +0900

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 > >Number:         32287
 > >Category:       kern
 > >Synopsis:       Processes hang in "mclpl"
 
 the attached patch is to fix the "hang" part of the problem.
 i'll commit it unless anyone objects.
 
 - pool_allocator_alloc: drain ourselves as well,
   so that pool_cache on us is drained as well.
 - pool_cache_put_paddr: destruct objects if underlying pool is starved.
 - pool_get: on kva starvation, wake up once a second and try again.
 
 of course, for longer term, it's better to have some kind of
 kva reclaim mechanism.
 
 YAMAMOTO Takashi
 
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 Index: subr_pool.c
 ===================================================================
 --- subr_pool.c	(revision 1470)
 +++ subr_pool.c	(revision 1471)
 @@ -929,13 +929,13 @@ pool_get(struct pool *pp, int flags)
  			/*
  			 * Wait for items to be returned to this pool.
  			 *
 -			 * XXX: maybe we should wake up once a second and
 -			 * try again?
 +			 * wake up once a second and try again,
 +			 * as the check in pool_cache_put_paddr() is racy.
  			 */
  			pp->pr_flags |= PR_WANTED;
  			/* PA_WANTED is already set on the allocator. */
  			pr_leave(pp);
 -			ltsleep(pp, PSWP, pp->pr_wchan, 0, &pp->pr_slock);
 +			ltsleep(pp, PSWP, pp->pr_wchan, hz, &pp->pr_slock);
  			pr_enter(pp, file, line);
  			goto startover;
  		}
 @@ -2019,6 +2019,10 @@ pool_cache_put_paddr(struct pool_cache *
  	struct pool_cache_group *pcg;
  	int s;
  
 +	if (__predict_false((pc->pc_pool->pr_flags & PR_WANTED) != 0)) {
 +		goto destruct;
 +	}
 +
  	simple_lock(&pc->pc_slock);
  
  	pcg = LIST_FIRST(&pc->pc_partgroups);
 @@ -2040,6 +2044,7 @@ pool_cache_put_paddr(struct pool_cache *
  		pcg = pool_get(&pcgpool, PR_NOWAIT);
  		splx(s);
  		if (pcg == NULL) {
 +destruct:
  
  			/*
  			 * Unable to allocate a cache group; destruct the object
 @@ -2249,8 +2254,8 @@ pool_allocator_alloc(struct pool *org, i
  		}
  
  		/*
 -		 * Drain all pools, except "org", that use this
 -		 * allocator.  We do this to reclaim VA space.
 +		 * Drain all pools, that use this allocator.
 +		 * We do this to reclaim VA space.
  		 * pa_alloc is responsible for waiting for
  		 * physical memory.
  		 *
 @@ -2271,8 +2276,6 @@ pool_allocator_alloc(struct pool *org, i
  		do {
  			TAILQ_REMOVE(&pa->pa_list, pp, pr_alloc_list);
  			TAILQ_INSERT_TAIL(&pa->pa_list, pp, pr_alloc_list);
 -			if (pp == org)
 -				continue;
  			simple_unlock(&pa->pa_slock);
  			freed = pool_reclaim(pp);
  			simple_lock(&pa->pa_slock);
 
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