[PATCH 3/3] fix-stop-sitting-printing-in-time-critical-context.patch

Cesar Eduardo Barros cesarb at cesarb.net
Wed Aug 27 14:03:08 CEST 2008

Andy Green escreveu:
> No, one doesn't expect the hardware USB unit to go insane until the
> device is reset because we were a little delayed servicing its
> interrupt!  I guess the same can happen in Linux if there was ever long
> service time ISR with higher priority that pushed out this one's latency.

Wait... THAT would explain why the USB gets stuck on cpufreq if it is in 
use during a frequency transition, but only if it is in use. The cpufreq 
frequency switch pauses the clock for the whole device for many clocks, 
while waiting for the PLL to recover. That's more than enough to cause a 
very high interrupt latency.

Cesar Eduardo Barros
cesarb at cesarb.net
cesar.barros at gmail.com

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