> Bad news, even with the rwsem after a lot more testing I can still
quoted text
> trigger the hang in ohci_hub_control() :-(
>
> I think we need to go back to considering the total serialization
> approach to this problem.

We shouldn't need that.  What happens if you add an msleep(5)
before ehci-hcd::ehci_run() drops ehci_cf_port_reset_rwsem?

The theory there being that the switch triggered by setting CF
doesn't take effect instantaneously, contrary to the effective
assumption of that code.  A delay of 5 msec seems like it should
be more than enough, but that's kind of a guess ... it's good to
keep that low, since unfortunately that's in the critical path
for OLPC "resume from idle".

- Dave

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