Re: [linux-usb-devel] [PATCH] Ohci-hcd: fix endless loop

[David Brownell <david-b@pacbell.net>]

On Thursday 25 November 2004 10:17, Colin Leroy wrote:
> Hi, 
> 
> Following patch fixes an endless loop that happens after having
> slept and resumed my iBook with a linux-wlan-ng controller plugged in,
> removed the stick and plugged it back (getting "IRQ lossage" message).

The infinite loop means that something trashed the stack, yes?

The "limit-- < -1000" test below should never be able to succeed
unless the previous "limit-- == 0" test got trashed by having
something obliterate the stack.  Possibly the driver for that WLAN
adapter.  Once that happens, all kinds of things will misbehave...

If you got the "IRQ INTR_SF lossage" diagnostic, there's clearly
some problem with IRQ handling after the resume ... is the iBook
firmware (or hardware) doing wierd stuff so that the normal PCI
IRQ calls stopped working?

And for that matter, "limit" is unsigned, so you must be getting
(and ignoring) some compiler warnings too.

This is not a good patch; not accepted.

- Dave


> Signed-off-by: Colin Leroy <colin@colino.net>
> --- a/drivers/usb/host/ohci-hcd.c	2004-11-25 19:00:25.000000000 +0100
> +++ b/drivers/usb/host/ohci-hcd.c	2004-11-25 19:08:59.000000000 +0100
> @@ -375,6 +375,11 @@
>  		spin_unlock_irqrestore (&ohci->lock, flags);
>  		set_current_state (TASK_UNINTERRUPTIBLE);
>  		schedule_timeout (1);
> +		if (limit-- < -1000) {
> +			ohci_warn (ohci, "Couldn't recover\n");
> +			ohci_restart(ohci);
> +			goto bail;
> +		}
>  		goto rescan;
>  	case ED_IDLE:		/* fully unlinked */
>  		if (list_empty (&ed->td_list)) {
> @@ -396,6 +401,7 @@
>  	dev->ep [epnum] = NULL;
>  done:
>  	spin_unlock_irqrestore (&ohci->lock, flags);
> +bail:
>  	return;
>  }
>  
> 
> 
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