From mboxrd@z Thu Jan  1 00:00:00 1970
From: arnd@arndb.de (Arnd Bergmann)
Date: Thu, 22 Oct 2015 12:29:13 +0200
Subject: [PATCH v2 6/6] vfio: platform: move get/put reset at open/release
In-Reply-To: <1445506922-6005-7-git-send-email-eric.auger@linaro.org>
References: <1445506922-6005-1-git-send-email-eric.auger@linaro.org>
 <1445506922-6005-7-git-send-email-eric.auger@linaro.org>
Message-ID: <4304536.D7eNHjlsvD@wuerfel>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Thursday 22 October 2015 11:42:02 Eric Auger wrote:
> Currently reset lookup is done on probe. This introduces a
> race with new registration mechanism in the case where the
> vfio-platform driver is bound to the device before its module
> is loaded: on the load, the probe happens which triggers the
> reset module load which itself attempts to get the symbol for
> the registration function (vfio_platform_register_reset). The
> symbol is not yet available hence the lookup fails. In case we
> do the lookup in the first open we are sure the vfio-platform
> module is loaded and vfio_platform_register_reset is available.
> 
> Signed-off-by: Eric Auger <eric.auger@linaro.org>

I don't understand the explanation. I would expect the request_module()
call to block until the module is actually loaded. Is this not
what happens?

>         mutex_unlock(&driver_lock);
> @@ -181,6 +182,8 @@ static int vfio_platform_open(void *device_data)
>                 if (ret)
>                         goto err_irq;
>  
> +               vfio_platform_get_reset(vdev);
> +
>                 if (vdev->reset)
>                         vdev->reset(vdev);
> 

This needs some error handling to ensure that the open() fails
if there is no reset handler.

	Arnd