Re: [PATCH] USB: fix deadlock in HCD code

From: Leonardo Chiquitto
Date: Wed May 21 2008 - 15:52:51 EST

>> > > Used in the suspend code. Your patch is indeed correct, but I fear
>> > > there might be a second bug caused by wrong calling conditions.
>> > The problem in the Novell bugzilla entry was caused by the fact that the
>> > OHCI irq routine was invoked with interrupts enabled, owing to a missing
>> > IRQF_DISABLED flag. That bug has already been fixed in 2.6.25.
>> That indeed is 2.6.25 kernel. I guess you are talking about commit
>> 442258e2ff69 here.
> Yes.
>> If so, the reporter is definitely using the kernel
>> containing this commit, and the lockups still trigger.
>> Seems that my patch is papering over the real bug (someone enabling
>> interrupts somewhere) indeed, but I can't seem to be able to find such
>> codepath.
> You could try testing the interrupt-enable flag at various places
> in ohci-hcd (start with finish_urb) and printing an error message if
> interrupts are enabled.
> One possibility is that in an earlier call to finish_urb,
> usb_hcd_giveback_urb was called with interrupts disabled and returned
> with interrupts enabled. In other words, some driver's callback
> routine may have enabled interrupts incorrectly.


I am trying your suggestion right now. Lets see if it finds something.


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