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Date:      Thu, 03 Aug 2006 14:51:35 -0500
From:      Eric Anderson <anderson@centtech.com>
To:        "R. B. Riddick" <arne_woerner@yahoo.com>
Cc:        freebsd-fs@freebsd.org
Subject:   Re: locking questions (regarding file systems)
Message-ID:  <44D253C7.6030108@centtech.com>
In-Reply-To: <20060803193633.91249.qmail@web30308.mail.mud.yahoo.com>
References:  <20060803193633.91249.qmail@web30308.mail.mud.yahoo.com>

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On 08/03/06 14:36, R. B. Riddick wrote:
> --- Eric Anderson <anderson@centtech.com> wrote:
>> On 08/03/06 01:14, R. B. Riddick wrote:
>>> --- Eric Anderson <anderson@centtech.com> wrote:
>>>> # here use_count is 1
>>>> 	error = vflush(mp, 1, flags, td);
>>>> 	if (error)
>>>> 		return (error);
>>>> 		
>>>> 	DROP_GIANT();
>>>> 	g_topology_lock();
>>>> # this is where the use_count is now zero, and it blocks
>>>> 	g_vfs_close(cp, td);
>>>> 	g_topology_unlock();
>>>> 	PICKUP_GIANT();
>>>> 	vrele(devvp);
>>>> 	
>>>> Is it blocking because the use_count is already 0?  Is the vflush 
>>>> breaking things?
>>>>
>>> >From the man page of vflush() I would guess, that u call it too early or
>>> unnecessarily...
>>>
>>> My feeling says: Open & Close it... ;-)
>>>
>>> Hmm... Did u try to run without vflush() and vrele()? :-)
>> I've tried getting rid of the vrele and vflush, and that doesn't help.
>>
> Hmm... So the g_vfs_close() always deadlocks with and without vflush()?
> That is strange... I mean: When I open a regular file, I can close it...

Correct..

> Did u try to call g_vfs_close() immediately after the g_vfs_open()?

I just did, and looks like the g_vfs_close directly after the g_vfs_open 
block (I copy-pasted) works ok.  When unmounting, it then panics on 
g_vfs_close, probably because it's already closed from before.

>> Any other ideas?  I have to be missing something very simple here..
>>
> Yes. Most likely it is something simple and orthogonal, because: Humans often
> have similar ideas of "simple"... ;-)
> 
> -Arne
> 
> 
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-- 
------------------------------------------------------------------------
Eric Anderson        Sr. Systems Administrator        Centaur Technology
Anything that works is better than anything that doesn't.
------------------------------------------------------------------------



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