linux-kernel - Re: [PATCH v2 1/2] mfd: viperboard: allocate I/O buffer separately

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Message-ID: <20140923073541.GM5237@localhost>
Date:	Tue, 23 Sep 2014 09:35:41 +0200
From:	Johan Hovold <johan@...nel.org>
To:	Octavian Purdila <octavian.purdila@...el.com>
Cc:	sameo@...ux.intel.com, lee.jones@...aro.org,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
	johan@...nel.org
Subject: Re: [PATCH v2 1/2] mfd: viperboard: allocate I/O buffer separately

On Mon, Sep 22, 2014 at 10:39:18PM +0300, Octavian Purdila wrote:
> Currently the I/O buffer is allocated part of the device status
> structure, potentially sharing the same cache line with other members
> in this structure.
> 
> Allocate the buffer separately, to avoid the I/O operations corrupting
> the device status structure due to cache line sharing.
> 
> Compiled tested only as I don't have access to hardware.
> 
> Signed-off-by: Octavian Purdila <octavian.purdila@...el.com>
> ---
>  drivers/mfd/viperboard.c       | 8 ++++++++
>  include/linux/mfd/viperboard.h | 2 +-
>  2 files changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mfd/viperboard.c b/drivers/mfd/viperboard.c
> index e00f534..5f62f4e 100644
> --- a/drivers/mfd/viperboard.c
> +++ b/drivers/mfd/viperboard.c
> @@ -64,6 +64,12 @@ static int vprbrd_probe(struct usb_interface *interface,
>  		return -ENOMEM;
>  	}
>  
> +	vb->buf = kzalloc(sizeof(struct vprbrd_i2c_write_msg), GFP_KERNEL);
> +	if (vb->buf == NULL) {
> +		ret = -ENOMEM;
> +		goto error;

This will cause a kref imbalance as you have a usb_put_dev in error,
but haven't done the get yet.

> +	}
> +
>  	mutex_init(&vb->lock);
>  
>  	vb->usb_dev = usb_get_dev(interface_to_usbdev(interface));

Here's the get.

Johan
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