Your analysis is correct, and your solution sounds reasonable.
Rhoads Hollowell
USB Software Team
Apple Computer, Inc.
On Oct 14, 2006, at 10:15 AM, Chris Cooksey wrote:
I am trying to get accurate time stamps during usb isoc-read
completion
routines. Looking at the darwin source code for GetBusFrameNumber()
I see
that no effort is made to guard for the possibility that my thread is
preempted between the time the AbsoluteTime is measured, and the
current bus
frame number is obtained.
I presume it is possible to be preempted in the kernel, and
depending on the
system load, I presume its possible to be in the ready queue for some
considerable time.
If I want super-accurate time stamps, should I repeat calls to
GetBusFrameNumber() until I can be sure that the call wasn't
interrupted?
Thanks,
Chris
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