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Message-ID: <d120d50005012605323111927a@mail.gmail.com>
Date: Wed, 26 Jan 2005 08:32:02 -0500
From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Reply-To: dtor_core@ameritech.net
To: johnpol@2ka.mipt.ru
Subject: Re: 2.6.11-rc2-mm1
Cc: Christoph Hellwig <hch@infradead.org>, Andrew Morton <akpm@osdl.org>,
       greg@kroah.com, linux-kernel@vger.kernel.org
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On Wed, 26 Jan 2005 11:31:07 +0300, Evgeniy Polyakov
<johnpol@2ka.mipt.ru> wrote:
> On Tue, 2005-01-25 at 22:42 +0000, Christoph Hellwig wrote:
> > > Yes, and it is better than removing module whose structures are in use.
> > > SuperIO core is asynchronous in it's nature, one can use logical device
> > > through superio core and remove it's module on other CPU, above loop
> > > will
> > > wait untill all reference counters are dropped.
> >
> > General rule is: increment module reference count while the hardware
> > is actually in use, and let device structures be allocated by the
> > bus core so drivers can be freed with them still allocated.  That's
> > how the driver model and thus about every other subsystem works.
> 
> It is not general rule - network stack does not have such mechanism,
> which is
> very good, I doubt each block device module increment it's module
> reference
> when it catch a request...
> It is internal structure that has reference counter, not module itself,
> and this
> structure may be in use, when module is unloaded, thus unloading must
> wait,
> untill all it's structures are freed.
> 

No, it does not necessarily has to wait. You can unload driver at any
time if you care to mark all its devices as "dead" and you have
generic release function in a separate module that does not get
unloaded until last registered device has been destroyed. Look for
example at serio code. I think USB is about the same.

-- 
Dmitry
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