Description of problem: 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. In order to prevent the tasklet function from occupying the cpu for a long time at a time, new URBS will not be added to the local_list even though the bh->head list is not empty. But also need to ensure the left URB giveback to be processed in time, so add a member high_prio for structure giveback_urb_bh to prioritize tasklet and schelule this tasklet again if bh->head list is not empty. At the same time, we are able to prioritize tasklet through structure member high_prio. So, replace the local high_prio_bh variable with this structure member in usb_hcd_giveback_urb. Version-Release number of selected component (if applicable): How reproducible: Steps to Reproduce: FIO/Iometer test： Test with Block size=4K, random read with libaio, and device performance>400 MB/s(better performance is recommended) . for example: Plextor EX1 128G, Asmedia usb3.1 gen+Samsung 960 SSD Actual results: Without this patch, you can see the noticeable lag of usb mouse or keyboard. Expected results: With this patch, Mouse and keyboard will not has any lag. Additional info:
merged: https://gitee.com/anolis/cloud-kernel/pulls/805