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Date: Sat, 28 Oct 2000 16:05:37 +0100
From: Philipp Rumpf <prumpf@parcelfarce.linux.theplanet.co.uk>
To: Brian Gerst <bgerst@didntduck.org>
Cc: Andrew Morton <andrewm@uow.edu.au>,
        Patrick van de Lageweg <patrick@bitwizard.nl>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Rogier Wolff <wolff@bitwizard.nl>,
        Linus Torvalds <torvalds@transmeta.com>
Subject: Re: [PROPOSED PATCH] ATM refcount + firestream
Message-ID: <20001028160537.C2272@parcelfarce.linux.theplanet.co.uk>
In-Reply-To: <Pine.LNX.4.21.0010270945510.13233-200000@panoramix.bitwizard.nl> <39F96BE1.B9C97C20@uow.edu.au> <20001028141518.A2272@parcelfarce.linux.theplanet.co.uk> <39FAD698.2FF9C8C8@didntduck.org> <20001028145312.B2272@parcelfarce.linux.theplanet.co.uk> <39FADAC9.DC1255D1@didntduck.org>
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In-Reply-To: <39FADAC9.DC1255D1@didntduck.org>; from bgerst@didntduck.org on Sat, Oct 28, 2000 at 09:55:21AM -0400
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On Sat, Oct 28, 2000 at 09:55:21AM -0400, Brian Gerst wrote:
> Yes, but they can be called (and sleep) with module refcount == 0.  This
> is because the file descripter used to perform the ioctl isn't directly
> associated with the network device, thereby not incrementing the
> refcount on open.

According to my proposal, it is perfectly safe to call a function in a module
while the module's use count is 0.  This function would typically look like this:

foo()
{
	MOD_INC_USE_COUNT;

	copy_*_user() (or anything else that sleeps);
	
	MOD_DEC_USE_COUNT;

	return bar;
}

The only difference to the "old" module scheme is that the above currently isn't
safe on SMP systems.
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