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Date:      Sun, 10 Nov 2002 21:01:14 -0800 (PST)
From:      Matthew Jacob <mjacob@feral.com>
To:        Jake Burkholder <jake@locore.ca>
Cc:        "Alan L. Cox" <alc@imimic.com>, jeff@freebsd.org, cvs-committers@freebsd.org, cvs-all@freebsd.org
Subject:   Re: cvs commit: src/sys/vm uma_dbg.c
Message-ID:  <Pine.BSF.4.21.0211102058500.64258-100000@beppo>
In-Reply-To: <20021110233436.C85338@locore.ca>

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> 
> This would be my suggestion:
> 
> Index: sys/vm/uma_core.c
> ===================================================================
> RCS file: /home/ncvs/src/sys/vm/uma_core.c,v
> retrieving revision 1.41
> diff -u -r1.41 uma_core.c
> --- sys/vm/uma_core.c	1 Nov 2002 01:01:27 -0000	1.41
> +++ sys/vm/uma_core.c	11 Nov 2002 04:11:38 -0000
> @@ -1348,7 +1348,9 @@
>  			    ("uma_zalloc: Bucket pointer mangled."));
>  			cache->uc_allocs++;
>  #ifdef INVARIANTS
> +			ZONE_LOCK(zone);
>  			uma_dbg_alloc(zone, NULL, item);
> +			ZONE_UNLOCK(zone);
>  #endif
>  			CPU_UNLOCK(zone, cpu);
>  			if (zone->uz_ctor)
> @@ -1698,10 +1700,12 @@
>  			    ("uma_zfree: Freeing to non free bucket index."));
>  			bucket->ub_bucket[bucket->ub_ptr] = item;
>  #ifdef INVARIANTS
> +			ZONE_LOCK(zone);
>  			if (zone->uz_flags & UMA_ZFLAG_MALLOC)
>  				uma_dbg_free(zone, udata, item);
>  			else
>  				uma_dbg_free(zone, NULL, item);
> +			ZONE_UNLOCK(zone);
>  #endif
>  			CPU_UNLOCK(zone, cpu);
>  			return;
> 
> uma_dbg_* are called with the zone lock held everywhere else, and the
> us_freelist is used with the zone lock held everywhere else as well.
> slab_zalloc is working on a newly created slab that doesn't have any
> other references, so it doesn't need to be locked until its added to
> the zone.
> 

And that'd be a no:

Mounting root from ufs:/dev/da2a
recursed on non-recursive lock (sleep mutex) NAMEI @
../../../vm/uma_dbg.c:202
first acquired @ ../../../vm/uma_core.c:1351
panic: recurse
cpuid = 2; 
panic
Stopped at      Debugger+0x34:  zapnot  v0,#0xf,v0      <v0=0x0>
db> t
Debugger() at Debugger+0x34
panic() at panic+0x1a4
witness_lock() at witness_lock+0x3fc
_mtx_lock_flags() at _mtx_lock_flags+0xc4
uma_dbg_getslab() at uma_dbg_getslab+0xe4
uma_dbg_alloc() at uma_dbg_alloc+0x30
uma_zalloc_arg() at uma_zalloc_arg+0x130
namei() at namei+0xa4
kern_mkdir() at kern_mkdir+0x70
start_init() at start_init+0x1a0
fork_exit() at fork_exit+0xe0
exception_return() at exception_return
--- root of call graph ---


I guess getting rid of the ZONE_LOCK in uma_dbg_getslab is also needed
:-)



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