I've looked at the POSIX spec to find the right way to portably
implement low overhead process synchronization.
I think the right way is to add _POSIX_THREAD_PROCESS_SHARED support
so that mutexes can be shared between processes.
There is something vague about the spec. I don't see that you can
reject "pthread_mutexattr_setpshared()" with EINVAL, and I don't
clearly see that the mutexes in existence after a fork are defined
to be a new set of mutexes with identical existing values. I have
to assume they are as mutexes can be statically allocated and there
is no way to ensure they are in a shared region without sharing
pages happening to contain mutexes with that attribute of the new
process space with the old one.
Assuming unique mutexes after a fork unless they happen to be in
a shared region, you could create a mutex in shared memory, apply
pthread_mutexattr_setpshared() to it, and then have the usual
pthread_mutex_lock()/pthread_mutex_unlock() interface support the
high performance synchronization.
Peter
--
Peter Dufault ([EMAIL PROTECTED]) Realtime development, Machine control,
HD Associates, Inc. Fail-Safe systems, Agency approval
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