Hello!
On 7/25/22 9:52 AM, Weitao Wang wrote:
> Usb core introduce the mechanism of giveback of URB in tasklet context to
> reduce hardware interrupt handling time. On some test situation(such as
> FIO with 4KB block size), when tasklet callback function called to
> giveback URB, interrupt handler add URB node to the bh->head list also.
> If check bh->head list again after finish all URB giveback of local_list,
> then it may introduce a "dynamic balance" between giveback URB and add URB
> to bh->head list. This tasklet callback function may not exit for a long
> time, which will cause other tasklet function calls to be delayed. Some
> real-time applications(such as KB and Mouse) will see noticeable lag.
>
> Fix this issue by taking new URBs giveback in next tasklet function call.
> Add a member high_prio for structure giveback_urb_bh and replace the local
> high_prio_bh variable with this structure member in usb_hcd_giveback_urb.
>
> Fixes: 94dfd7edfd5c ("USB: HCD: support giveback of URB in tasklet context")
> Signed-off-by: Weitao Wang <WeitaoWang-oc@xxxxxxxxxxx>
> ---
> v1->v2:
> - Fix compile warning by remove label "restart".
> - Modify the patch description info.
> - Change structure member from hi_priority to high_prio.
>
> drivers/usb/core/hcd.c | 25 ++++++++++++++-----------
> include/linux/usb/hcd.h | 1 +
> 2 files changed, 15 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
> index 06eea8848ccc..1feb9a604380 100644
> --- a/drivers/usb/core/hcd.c
> +++ b/drivers/usb/core/hcd.c
[...]
> @@ -2959,6 +2961,7 @@ int usb_add_hcd(struct usb_hcd *hcd,
>
> /* initialize tasklets */
> init_giveback_urb_bh(&hcd->high_prio_bh);
> + hcd->high_prio_bh.high_prio = 1;
s/1/true/?
> init_giveback_urb_bh(&hcd->low_prio_bh);
>
> /* enable irqs just before we start the controller,
> diff --git a/include/linux/usb/hcd.h b/include/linux/usb/hcd.h
> index 2c1fc9212cf2..98d1921f02b1 100644
> --- a/include/linux/usb/hcd.h
> +++ b/include/linux/usb/hcd.h
> @@ -66,6 +66,7 @@
>
> struct giveback_urb_bh {
> bool running;
> + bool high_prio;
> spinlock_t lock;
> struct list_head head;
> struct tasklet_struct bh;
MBR, Sergey
