Hi David,
> When disconnecting a bcm203x device we kill and destroy the usb-urb, however,
> there might still be a pending work-structure which resubmits the now invalid
> urb. To avoid this race condition, we simply set a shutdown-flag and
> synchronously kill the worker first.
>
> This also adds a comment to all schedule_work()s, as it is really not clear
> that they are used as replacement for short timers (which can be seen in the git
> history).
>
> Signed-off-by: David Herrmann <dh.herrmann@xxxxxxxxxxxxxx>
> ---
> drivers/bluetooth/bcm203x.c | 12 ++++++++++++
> 1 files changed, 12 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/bluetooth/bcm203x.c b/drivers/bluetooth/bcm203x.c
> index 8b1b643..6b42732 100644
> --- a/drivers/bluetooth/bcm203x.c
> +++ b/drivers/bluetooth/bcm203x.c
> @@ -24,6 +24,7 @@
>
> #include <linux/module.h>
>
> +#include <linux/atomic.h>
> #include <linux/kernel.h>
> #include <linux/init.h>
> #include <linux/slab.h>
> @@ -65,6 +66,7 @@ struct bcm203x_data {
> unsigned long state;
>
> struct work_struct work;
> + atomic_t shutdown;
>
> struct urb *urb;
> unsigned char *buffer;
> @@ -97,6 +99,7 @@ static void bcm203x_complete(struct urb *urb)
>
> data->state = BCM203X_SELECT_MEMORY;
>
> + /* use workqueue to have a small delay */
> schedule_work(&data->work);
> break;
>
> @@ -155,6 +158,10 @@ static void bcm203x_work(struct work_struct *work)
> struct bcm203x_data *data =
> container_of(work, struct bcm203x_data, work);
>
> + smp_rmb();
> + if (atomic_read(&data->shutdown))
> + return;
> +
> if (usb_submit_urb(data->urb, GFP_ATOMIC) < 0)
> BT_ERR("Can't submit URB");
> }
> @@ -243,6 +250,7 @@ static int bcm203x_probe(struct usb_interface *intf, const struct usb_device_id
>
> usb_set_intfdata(intf, data);
>
> + /* use workqueue to have a small delay */
> schedule_work(&data->work);
>
> return 0;
> @@ -254,6 +262,10 @@ static void bcm203x_disconnect(struct usb_interface *intf)
>
> BT_DBG("intf %p", intf);
>
> + atomic_inc(&data->shutdown);
> + smp_wmb();
> + cancel_work_sync(&data->work);
> +
can you quickly explain to me why we need the memory barrier here.
Regards
Marcel
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