Kernel Bug Tracker – Bug 5433
modprobe ehci-hcd freezes system
Last modified: 2005-11-14 21:43:29 UTC
Most recent kernel where this bug did not occur: Something between 2.6.10 and 2.6.12
Hardware Environment: x86, P4
Software Environment: Gentoo ~x86 (testing)
after modprobe ehci-hcd the system does not respond any more
Steps to reproduce:
See http://bugs.gentoo.org/show_bug.cgi?id=108919 for more information
*** This bug has been marked as a duplicate of 5428 ***
I was able to track down a similar problem on my computer. The entire system
doesn't hang, only the modprobe process. The hang occurs in the following pathway:
usb_add_hcd -> ehci_reset -> ehci_port_power -> ehci_hub_control
As part of its startup, ehci_hub_control tries to acquire ehci->lock. However
the spinlock has not yet been initialized, and so modprobe hangs.
I don't know how David will want to fix this.
Hmm, I suspect the root cause is that the root hub init changes didn't
involve adding a new init() method ... the original reset() method
did that, but the new one assumes that's already been done. And
reset() of course needs to be done without necessarily initializing
HCD data structures. An add() should init() then later reset().
This would seem to explain another report I've gotten on the 2.6.15
queue; thanks Alan! (I'm actually surprised that OHCI never sees
this problem... the reason is that it's got a stupid reset method,
which ignores the failures that can happen when reset-at-runtime
More info on this. This isn't an issue with 2.6.14-rc4 since
the first thing done by ehci_hc_reset() is to initialize
that spinlock. But it's an issue with the 2.6.15 prepatches.
I disabled "Enable legacy USB support" in kernel and after that it works. It
would be better of course if that would not cause a system freeze but at least I
know how to fix this problem now.
On Mon, Oct 17, 2005 at 10:36:55AM -0700, email@example.com wrote:
> I disabled "Enable legacy USB support" in kernel
You mean, in the BIOS, not kernel, right?
In the BIOS of course. Stupid me.
Great, glad we have a fix.