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mpv/misc/rendezvous.h
wm4 559fe1daac Add Plan 9-style barriers
Plan 9 has a very interesting synchronization mechanism, the
rendezvous() call. A good property of this is that you don't need to
explicitly initialize and destroy a barrier object, unlike as with e.g.
POSIX barriers (which are mandatory to begin with). Upon "meeting", they
can exchange a value.

This mechanism will be nice to synchronize certain stages of
initialization between threads in the following commit.

Unlike Plan 9 rendezvous(), this is not implemented with a hashtable,
because that would require additional effort (especially if you want to
make it actually scele). Unlike the Plan 9 variant, we use intptr_t
instead of void* as type for the value, because I expect that we will be
mostly passing a status code as value and not a pointer. Converting an
integer to void* requires two cast (because the integer needs to be
intptr_t), the other way around it's only one cast.

We don't particularly care about performance in this case either. It's
simply not important for our use-case. So a simple linked list is used
for waiters, and on wakeup, all waiters are temporarily woken up.
2014-07-26 20:29:48 +02:00

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C

#ifndef MP_RENDEZVOUS_H_
#define MP_RENDEZVOUS_H_
#include <stdint.h>
intptr_t mp_rendezvous(void *tag, intptr_t value);
#endif