Hi,
Nicolas Saenz Julienne <nicolassaenzj@xxxxxxxxx> writes:
> __dwc3_gadget_wakeup() is called while holding a spinlock, then depends on
> jiffies in order to timeout while polling the USB core for a link state
> update. In the case the wakeup failed, the timeout will never happen and
> will also cause the cpu to stall until rcu_preempt kicks in.
>
> This switches to a "decrement variable and wait" timeout scheme.
>
> Signed-off-by: Nicolas Saenz Julienne <nicolassaenzj@xxxxxxxxx>
> ---
> drivers/usb/dwc3/gadget.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 8f8c215..d0c711f 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -1433,7 +1433,7 @@ static int dwc3_gadget_get_frame(struct usb_gadget *g)
>
> static int __dwc3_gadget_wakeup(struct dwc3 *dwc)
> {
> - unsigned long timeout;
> + int retries;
>
> int ret;
> u32 reg;
> @@ -1484,14 +1484,16 @@ static int __dwc3_gadget_wakeup(struct dwc3 *dwc)
> }
>
> /* poll until Link State changes to ON */
> - timeout = jiffies + msecs_to_jiffies(100);
> + retries = 20000;
>
> - while (!time_after(jiffies, timeout)) {
> + while (retries--) {
> reg = dwc3_readl(dwc->regs, DWC3_DSTS);
>
> /* in HS, means ON */
> if (DWC3_DSTS_USBLNKST(reg) == DWC3_LINK_STATE_U0)
> break;
> +
> + udelay(5);
let's just drop this udelay() here. It's very likely this will switch
the link state much quicker than 100ms anyway. Other than that, nice
catch :-)
--
balbi
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