On 02/14/2012 12:36 PM, Henry Vermaak wrote:
No, you're wrong.
I did a lot of research on pthread_mutex.. and I do know that it uses
Futex when the underlying system provides same (not all Linux
implementations on all architectures do have Futex). Thus unless you
take additional care it can't be uses in an inter-process was.
I don't doubt that it is possible to use pthread_mutex.. for system wide
semaphores, but as it uses user space memory you (at least) need to
provide shared memory for the processes in question (and thus do
something that is not the "standard" usage of the pthread-library. I
never tried this. But I did try system 5 semaphores (also with FPC) some
years ago and this did work nicely.
If Futex (via pthreadlib) really does work, it of course is faster than
system5 semas, as in most cases a context switch can be avoided.
-Michael
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