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Date:      Wed, 15 Sep 2010 16:57:15 +0200
From:      Attilio Rao <attilio@freebsd.org>
To:        Kostik Belousov <kostikbel@gmail.com>
Cc:        svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org
Subject:   Re: svn commit: r212661 - head/sys/dev/aac
Message-ID:  <AANLkTikMxAZDa9KGvY-aPfCJ=gQL0gNpF5Marsbw-Wuv@mail.gmail.com>
In-Reply-To: <20100915145209.GK2465@deviant.kiev.zoral.com.ua>
References:  <201009151424.o8FEOLZE039185@svn.freebsd.org> <20100915145209.GK2465@deviant.kiev.zoral.com.ua>

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2010/9/15 Kostik Belousov <kostikbel@gmail.com>:
> On Wed, Sep 15, 2010 at 02:24:21PM +0000, Attilio Rao wrote:
>> Author: attilio
>> Date: Wed Sep 15 14:24:21 2010
>> New Revision: 212661
>> URL: http://svn.freebsd.org/changeset/base/212661
>>
>> Log:
>> =C2=A0 Fix bogus busying mechanism from cdevsw callbacks:
>> =C2=A0 - D_TRACKCLOSE may be used there as d_close() are expected to mat=
ch up
>> =C2=A0 =C2=A0 d_open() calls
> VFS is not very good at properly calling VOP_CLOSE(). As example, prematu=
re
> vnode reclaim due to devfs unmount would cause VOP_CLOSE() to be called
> only once despite the number of opens being =C2=A0> 1.

Yes.
That makes implementing a similar semantic in drivers very difficult
and not very well fixable, in particular within the d_* callbacks.
I'm seriously wondering if we might just make a shortcut just for
supporting such a feature (busying the device on real devfs entry
activity) as several of them may be needing and may be probabilly
needing to be 100%.
Luckilly, it seems that such paths are not experienced very frequently.

Attilio


--=20
Peace can only be achieved by understanding - A. Einstein



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