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Date:      Mon, 13 May 2002 17:42:53 +0700 (ALMST)
From:      Boris Popov <bp@butya.kz>
To:        "Semen A. Ustimenko" <semenu@FreeBSD.org>
Cc:        freebsd-fs@FreeBSD.org, freebsd-hackers@FreeBSD.org, "Flood, Jim" <Jim.Flood@acirro.com>
Subject:   Re: NULLFS-related possible deadlock + fix proposal
Message-ID:  <Pine.BSF.4.21.0205131728290.16895-100000@lion.butya.kz>
In-Reply-To: <20020511005932.S1705-100000@def.the.net>

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On Sat, 11 May 2002, Semen A. Ustimenko wrote:

> DEADLOCK...

	Indeed, weird situation. Nice analysis, btw :)

> Make vn_lock() in vrele() lock vnode only LK_THISLAYER. Obviously, the
> NULLFS and other stacking FSes will have to deal with this in their
> VOP_INACTIVE() handlers. This changes won't touch real FSes as they ignore
> the LK_THISLAYER, don't they?

	Yes, you're correct in that LK_THISLAYER currently used only by
"stacked" filesystem(s) and it used exactly for such situations to avoid
deadlocks.  The proposed solution may even work without any additional
code because null_inactive() performs its own management on the lower
vnode locking.

-- 
Boris Popov
http://rbp.euro.ru


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