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From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Andrew Morton <akpm@osdl.org>
Subject: Re: 2.6.15-rc5-mm2: ehci_hcd crashes on load sometimes
Date: Mon, 12 Dec 2005 21:55:43 +0100
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On Monday, 12 December 2005 21:29, Andrew Morton wrote:
> "Rafael J. Wysocki" <rjw@sisk.pl> wrote:
> >
> > On Sunday, 11 December 2005 21:38, Andrew Morton wrote:
> > > "Rafael J. Wysocki" <rjw@sisk.pl> wrote:
> > > >
> > > > The ehci_hcd driver causes problems like this:
> > > > 
> > > > ehci_hcd 0000:00:02.2: EHCI Host Controller
> > > > ehci_hcd 0000:00:02.2: debug port 1
> > > > ehci_hcd 0000:00:02.2: new USB bus registered, assigned bus number 3
> > > > ehci_hcd 0000:00:02.2: irq 5, io mem 0xfebfdc00
> > > > usb 2-2: Product: USB Receiver
> > > > usb 2-2: Manufacturer: Logitech
> > > > usb 2-2: configuration #1 chosen from 1 choice
> > > > ehci_hcd 0000:00:02.2: USB 2.0 started, EHCI 1.00, driver 10 Dec 2004
> > > > Unable to handle kernel NULL pointer dereference at 00000000000002a4 RIP:
> > > > <ffffffff880ad9d0>{:ehci_hcd:ehci_irq+224}
> > > 
> > > Can you poke around in gdb, see which line it's dying at?
> > 
> > It looks like at the line 620.  At least here's what gdb told me:
> > 
> > Line 620 of "ehci-hcd.c" starts at address 0x69c3 <ehci_irq+211>
> >    and ends at 0x69e2 <ehci_irq+242>.
> 
> On my tree that's
> 
> 	if ((status & STS_PCD) && device_may_wakeup(&hcd->self.root_hub->dev)) {

Yes, that's it.

> It's best to actually send a copy of line 620 - kernels vary a lot, and
> many developers won't have that particualr -mm tree handy.
> 
> The way I normally do this is to do `gdb vmlinux' and then `l
> *0xffffffff880ad9d0'.

Does it work for modules too?

> If that lands you in some inline function then poke 
> around, displacing the EIP by +/- amounts until it lands outside the
> inlined function so you can see the callsite.
> 
> Anyway.  Greg's tree seems rather buggy lately..

Well ...

-- 
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