linux-kernel - Re: [PATCH] Revert "spi/doc: spi_master

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Message-ID: <20120904072523.GB28643@pengutronix.de>
Date:	Tue, 4 Sep 2012 09:25:23 +0200
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	spi-devel-general@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org,
	Grant Likely <grant.likely@...retlab.ca>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	kernel@...gutronix.de
Subject: Re: [PATCH] Revert "spi/doc: spi_master_put must be followed up by
 kfree"

On Mon, Sep 03, 2012 at 01:26:26PM -0700, Guenter Roeck wrote:
> Actually, spi_master_put() after spi_alloc_master() must _not_ be followed
> by kfree(). The memory is already freed with the call to spi_master_put()
> through spi_master_class, which registers a release function. Calling both
> spi_master_put() and kfree() results in often nasty (and delayed) crashes
> elsewhere in the kernel, often in the networking stack.
> 
> This reverts commit eb4af0f5349235df2e4a5057a72fc8962d00308a.
> 
> Cc: Uwe Kleine-Koenig <u.kleine-koenig@...gutronix.de>
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
I didn't check the callback, but I introduced
eb4af0f5349235df2e4a5057a72fc8962d00308a because I saw the kfree in
drivers/spi/spi-imx.c. So I guess this needs fixing, too?!

Best regards
Uwe

> ---
>  drivers/spi/spi.c |    3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
> index 2d9b5bb..6470750 100644
> --- a/drivers/spi/spi.c
> +++ b/drivers/spi/spi.c
> @@ -1082,8 +1082,7 @@ static struct class spi_master_class = {
>   *
>   * The caller is responsible for assigning the bus number and initializing
>   * the master's methods before calling spi_register_master(); and (after errors
> - * adding the device) calling spi_master_put() and kfree() to prevent a memory
> - * leak.
> + * adding the device) calling spi_master_put() to prevent a memory leak.
>   */
>  struct spi_master *spi_alloc_master(struct device *dev, unsigned size)
>  {

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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