FreeBSD support for _POSIX_THREAD_PROCESS_SHARED is incomplete and buggy, avoid it.

Author: igaztanaga

.github/workflows/ci.yml

@@ -927,10 +927,6 @@ jobs:
             then
                 echo "Executing: sudo pkg git bash python3 curl"
                 sudo pkg install -y git bash python3 curl
-                # Enable persistent umtx for vnode-backed shared memory synchronization
-                # This is needed for process-shared pthread mutexes in memory-mapped files
-                echo "Setting kern.ipc.umtx_vnode_persistent=1"
-                sudo sysctl kern.ipc.umtx_vnode_persistent=1
             fi
             if [ "${{matrix.vm}}" == "openbsd" ]
             then

include/boost/interprocess/detail/workaround.hpp

@@ -65,6 +65,14 @@
          //https://opensource.apple.com/source/libpthread/libpthread-301.30.1/src/pthread_cond.c.auto.html
          //in method pthread_cond_wait
          #define BOOST_INTERPROCESS_BUGGY_POSIX_PROCESS_SHARED
+      #elif defined(__FreeBSD__)
+         //The FreeBSD implementation is not workable for Interprocess as data structures
+         //hold raw pointers and even "kern.ipc.umtx_vnode_persistent" does not solve this issue
+         //because de vnode will be recycled anyway since it is only useful when:
+         // - Multiple processes have the file mapped **simultaneously**
+         // - The kernel needs to coordinate their wait queues
+         //See (https://man.freebsd.org/cgi/man.cgi?query=libthr) for details
+         #define BOOST_INTERPROCESS_BUGGY_POSIX_PROCESS_SHARED
       #endif
 
       //If buggy _POSIX_THREAD_PROCESS_SHARED is detected avoid using it