linux-kernel - Re: [PATCH] platform_driver_register: warn if probe is in .init.text

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Message-ID: <20100122234936.GA14538@core.coreip.homeip.net>
Date:	Fri, 22 Jan 2010 15:49:37 -0800
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
Cc:	Greg KH <gregkh@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] platform_driver_register: warn if probe is in .init.text

Hi Uwe,

On Fri, Jan 22, 2010 at 08:49:18PM +0100, Uwe Kleine-König wrote:
> +int platform_driver_register(struct platform_driver *drv)
> +{
> +	int ret = __platform_driver_register(drv);
> +
> +#if defined(CONFIG_HOTPLUG)
> +	/*
> +	 * drivers that are registered by platform_driver_register
> +	 * should not have their probe function in .init.text.  The
> +	 * reason is that a probe can happen after .init.text is
> +	 * discarded which then results in an oops.  The alternatives
> +	 * are using .devinit.text for the probe function or "register"
> +	 * with platform_driver_probe.
> +	 */


What about CONFIG_MODULE case (without hotplug)? The driver may be
compiled in (and thus probe will be discarded) but device might be
created by a loadable module which is loaded later.

> +	if (drv->probe && kernel_init_text_address((unsigned long)drv->probe))
> +		pr_warning("oops-warning: probe function of platform driver %s"
> +			       " lives in .init.text\n", drv->driver.name);
> +#else
> +	/*
> +	 * without HOTPLUG probe functions can be discarded after the driver is
> +	 * loaded.
> +	 * There is a little chance for false positives, namely if the driver is
> +	 * registered after the .init sections are discarded.
> +	 */
> +	if (drv->probe && !kernel_init_text_address((unsigned long)drv->probe))
> +		pr_info("probably the probe function of platform driver %s can"
> +				" be moved to .init.text\n", drv->driver.name);

It really depends on the user's (or rather builder's) local
configuration so how can we make this suggestion?

Thanks.

-- 
Dmitry
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