Bin, Marek,
Would you take a look at xHCI code?
Lots of xHCI code invokes BUG_ON()/BUG()
when the hardware access fails,
then halts the system completely.
This is not a software bug.
2018-01-10 10:45 GMT+09:00 Masahiro Yamada <yamada.masah...@socionext.com>:
> xhci_wait_for_event() is supposed to return a pointer to union xhci_trb,
> but it does not return anything at the end of the function.
>
> This relies on that the end of the function is unreachable due to BUG().
>
> We are planning to make BUG() no-op for platforms with strong image size
> constraint. Doing so would cause compiler warning:
>
> drivers/usb/host/xhci-ring.c:475:1: warning: control reaches end of non-void
> function [-Wreturn-type]
> }
> ^
>
> So, this function must return something. From the error message just
> above, ERR_PTR(-ETIMEDOUT) seems a good choice.
>
> The use of BUG() looks suspicious here in the first place; no response
> from hardware is not a bug. It should be treated as a normal error.
> So, this function must return an error pointer instead of BUG(), then
> the caller must handle it properly.
>
> I am not fixing the code because this is not the only place that stops
> the system. Just one failure of xHCI halts the system, here and there.
>
> I left a comment block, hoping somebody will take a look.
>
> Signed-off-by: Masahiro Yamada <yamada.masah...@socionext.com>
> ---
>
> Changes in v3:
> - newly added
>
> Changes in v2: None
>
> drivers/usb/host/xhci-ring.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
> index 579e670..d780367 100644
> --- a/drivers/usb/host/xhci-ring.c
> +++ b/drivers/usb/host/xhci-ring.c
> @@ -471,7 +471,14 @@ union xhci_trb *xhci_wait_for_event(struct xhci_ctrl
> *ctrl, trb_type expected)
> return NULL;
>
> printf("XHCI timeout on event type %d... cannot recover.\n",
> expected);
> +
> + /*
> + * CHECK:
> + * Is this software bug? Is this a good reason to halt the system?
> + */
> BUG();
> +
> + return ERR_PTR(-ETIMEDOUT);
> }
>
> /*
> --
> 2.7.4
>
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--
Best Regards
Masahiro Yamada
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