[linux-audio-dev] non-RT thread waiting for RT thread

[Ken McMillan]

I've been puzzling over something that I thought
someone on this list
might have a good solution for.  I need to make a low
priority
(non-real time) thread wait for a real time thread to
do something. I
can't use a semaphore or condition variable for this,
because that
would mean the low priority thread must briefly take a
lock while
examining the condition variable or sempahore. If it
were to be
pre-empted while holding this lock, the RT thread
could block waiting
to obtain the lock in order to signal the condition or
modify the
semaphore.

I could prevent this by raising the priority of the
low priority
thread before taking the lock, but I don't know how to
do this in
a portable way (i.e., I want my app to port to windows
and mac, but
even on "posix compliant" systems, getting RT
privileges seems to
be pretty system-dependent).

It occurs to me that I could just "busy wait" using a
timer, which
would work but is a bit inelegant. Has anyone else
come up with a good
solution for this problem?

Thanks for any thoughts -- Ken McMillan


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