Re: [PATCH] USB: HCD: Fix URB giveback issue in tasklet function

[WeitaoWang-oc@xxxxxxxxxxx]

On 2022/7/21 21:50, Alan Stern wrote:
> On Thu, Jul 21, 2022 at 02:08:33PM +0800, 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.
>
> The patch also replaces the local high_prio_bh variable with a new
> bh->high_prio structure member.  This should be mentioned in the patch
> description.
>
> Alan Stern
> .
Okay,I will take your suggestion and submit a revised version.

Thanks
weitao