pkgsrc/x11/libxshmfence/DESCR
tnn 7ce1fc7443 Add makeshift NetBSD support using POSIX semaphores.
Not upstreamed because I think NetBSD should be given the chance to
implement some better interprocess synchronization primitives first.
See PR lib/49529.

In particular what's missing is an interprocess sync primitive that can:
  1) be passed safely through MAP_SHARED memory
  2) support atomic unlock-and-block (like pthread_cond_wait)
  3) wake up all waiters at once
2015-09-24 23:34:16 +00:00

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This library offers a CPU-based synchronization primitive compatible
with the X SyncFence objects that can be shared between processes
using file descriptor passing.
There are four underlying implementations:
1) On Linux, the library uses futexes
2) On FreeBSD, the library uses umtx
3) On NetBSD, the library uses POSIX semaphores (for now)
4) On other systems, the library uses posix mutexes and condition
variables.