linux-kernel - Re: [v4l-dvb-maintainer] [patch, -git] drivers/media build fix for modular builds

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Message-ID: <Pine.LNX.4.58.0804301442010.9894@shell4.speakeasy.net>
Date:	Wed, 30 Apr 2008 14:52:05 -0700 (PDT)
From:	Trent Piepho <xyzzy@...akeasy.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Mike Galbraith <efault@....de>, sfr@...b.auug.org.au,
	video4linux-list@...hat.com, Sam Ravnborg <sam@...nborg.org>,
	linux-kernel@...r.kernel.org, mchehab@...radead.org,
	linux-dvb-maintainer@...uxtv.org, Ingo Molnar <mingo@...e.hu>,
	torvalds@...ux-foundation.org, David Miller <davem@...emloft.net>
Subject: Re: [v4l-dvb-maintainer] [patch,	-git] drivers/media build fix for
 modular builds

On Wed, 30 Apr 2008, Andrew Morton wrote:
> Does this make it feel better?
>
> --- a/drivers/media/video/tuner-core.c~a
> +++ a/drivers/media/video/tuner-core.c
> @@ -40,11 +40,11 @@
>  	typeof(&FUNCTION) __a = symbol_request(FUNCTION); \
>  	if (__a) { \
>  		__r = (int) __a(ARGS); \
> +		symbol_put(FUNCTION); \
>  	} else { \
>  		printk(KERN_ERR "TUNER: Unable to find " \
>  				"symbol "#FUNCTION"()\n"); \
>  	} \
> -	symbol_put(FUNCTION); \
>  	__r; \
>  })

Should the symbol_put be done at all?  When I wrote the code this is based
on, it would check if FUNCTION failed or not.  If it failed, the symbol was
put.  But if it worked, then one was returned a handle into FUNCTION's
module, and so the symbol was not put.  If it was, the module's refcount
would be zero but the caller would have a handle into the module.

So if FUNCTION does anything that creates references to the module, and it
doesn't inc it's own refcount, then the symbol_put shouldn't be done.
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