On Sun, 13 Sep 2015, Roland Weber wrote:

> I compiled a kernel 3.17(.0) with my additional debug lines...
> and this one does NOT freeze! The output is:
> 
> (first unbind)
> ehci-pci 0000:00:1d.0: remove, state 4
> ehci-pci 0000:00:1d.0: roothub graceful disconnect
> usb usb1: USB disconnect, device number 1
> ehci-pci 0000:00:1d.0: shutdown urb ffff880072bf4300 ep1in-intr
> usb_remove_hcd: calling stop
> ehci-pci 0000:00:1d.0: stop
> ehci_silence_controller: entry
> ehci_halt: entry
> ehci_halt: after spin_lock_irq
> ehci_halt: about to readl prematurely
> ehci_halt: premature readl returned 10001

Note: 10001 instead of 10000, which is what you saw in the other 
kernel.  That could be highly relevant.

> I cannot yet tell whether the difference between freeze and non-freeze
> is due to code changes, or because I used a different kernel config.
> (It brings down compilation times from 3h to 2h.)
> 
> So next I'll compile 3.17.8 with my config.

On Sun, 13 Sep 2015, Roland Weber wrote:

> Actually, it made more sense to try other precompiled kernels.
> I can freeze the precompiled 3.17.0 with unbind/bind/unbind,
> but not the one I compiled myself. I'm currently compiling
> 3.17.0 with the exact config of the precompiled kernel, to
> rule out differences in the build environment as the cause.
> 
> Assuming that this kernel does freeze, I will start to 'bisect' the
> differences in the kernel configurations, based on the assumption
> that it might give us a clue about where the problem comes from.
> I expect this to take several days... please stop me if you've got
> a better lead.

At some point along the way, can you try adding some printk statements 
to ehci_suspend() and ehci_resume() in ehci-hcd.c?  I'd like to know if 
they get called during the bind/unbind procedure and are responsible 
for that 10001 vs. 10000 value.

Alan Stern

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