On Tuesday 09 April 2013 18:02:27 Dan Williams wrote:
> Some drivers (sierra_net) need the status interrupt URB
> active even when the device is closed, because they receive
> custom indications from firmware. Add functions to refcount
> the status interrupt URB submit/kill operation so that
> sub-drivers and the generic driver don't fight over whether
> the status interrupt URB is active or not.
>
> A sub-driver can call usbnet_status_start() at any time, but
> the URB is only submitted the first time the function is
> called. Likewise, when the sub-driver is done with the URB,
> it calls usbnet_status_stop() but the URB is only killed when
> all users have stopped it. The URB is still killed and
> re-submitted for suspend/resume, as before, with the same
> refcount it had at suspend.
>
> Signed-off-by: Dan Williams <dcbw@xxxxxxxxxx>
> ---
> drivers/net/usb/usbnet.c | 79 ++++++++++++++++++++++++++++++++++++++++++----
> include/linux/usb/usbnet.h | 5 +++
> 2 files changed, 77 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
> index 51f3192..e8b363a 100644
> --- a/drivers/net/usb/usbnet.c
> +++ b/drivers/net/usb/usbnet.c
> @@ -42,7 +42,7 @@
> #include <linux/workqueue.h>
> #include <linux/mii.h>
> #include <linux/usb.h>
> -#include <linux/usb/usbnet.h>
> +#include "usbnet.h"
> #include <linux/slab.h>
> #include <linux/kernel.h>
> #include <linux/pm_runtime.h>
> @@ -252,6 +252,70 @@ static int init_status (struct usbnet *dev, struct usb_interface *intf)
> return 0;
> }
>
> +/* Submit the interrupt URB if it hasn't been submitted yet */
> +static int __usbnet_status_start(struct usbnet *dev, gfp_t mem_flags,
> + bool force)
> +{
> + int ret = 0;
> + bool submit = false;
> +
> + if (!dev->interrupt)
> + return 0;
> +
> + mutex_lock(&dev->interrupt_mutex);
> +
> + if (force) {
That design means that interrupt_count isn't accurate if force is used.
That is extremely ugly.
> + /* Only submit now if the URB was previously submitted */
> + if (dev->interrupt_count)
> + submit = true;
> + } else if (++dev->interrupt_count == 1)
> + submit = true;
> +
> + if (submit)
> + ret = usb_submit_urb(dev->interrupt, mem_flags);
> +
> + dev_dbg(&dev->udev->dev, "incremented interrupt URB count to %d\n",
> + dev->interrupt_count);
> + mutex_unlock(&dev->interrupt_mutex);
> + return ret;
> +}
> +
> +int usbnet_status_start(struct usbnet *dev, gfp_t mem_flags)
> +{
> + /* Only drivers that implement a status hook should call this */
> + BUG_ON(dev->interrupt == NULL);
> +
> + if (test_bit(EVENT_DEV_ASLEEP, &dev->flags))
> + return -EINVAL;
This looks like a race condition.
> + return __usbnet_status_start(dev, mem_flags, false);
> +}
> +EXPORT_SYMBOL_GPL(usbnet_status_start);
> +
> +/* Kill the interrupt URB if all submitters want it killed */
> +static void __usbnet_status_stop(struct usbnet *dev, bool force)
> +{
> + if (dev->interrupt) {
> + mutex_lock(&dev->interrupt_mutex);
> + if (!force)
> + BUG_ON(dev->interrupt_count == 0);
> +
> + if (force || --dev->interrupt_count == 0)
> + usb_kill_urb(dev->interrupt);
Why so complicated? If it may be on, kill it unconditionally.
> +
> + dev_dbg(&dev->udev->dev,
> + "decremented interrupt URB count to %d\n",
> + dev->interrupt_count);
> + mutex_unlock(&dev->interrupt_mutex);
> + }
> +}
> +
Regards
Oliver
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