It certainly looks like you've found a flaw in the core kernel. Or
else a subtle hardware flaw in your CPU...
Just to be certain, take out all your new code and instead add a simple
test at the start of usb_hcd_irq() in hcd.c. That routine is the
registered handler for USB interrupts. If interrupts are ever enabled
at that spot, then something is badly wrong.
You might also keep track of the total number of each type of call, so
whenever you find interrupts are enabled, you can print out something
like this:
usb_hcd_irq(): interrupts disabled %d, enabled %d
where the two values are the numbers of times the routine has been
called with interrupts off or on, respectively. You don't have to run
this for a long time; since the test code should _never_ trigger, any
output at all will indicate a real problem.
When you get that, change the Subject of your email to make it more
noticeable. A line like:
BUG in 2.6.26-rc8 interrupt handling!
should draw people's attention. :-) Include a description of the
problem and a copy of /proc/interrupts.
Alan Stern
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