sharing read-write lock between interprocess

I have two processes rwlock1(parent) and rwlock2(child) . i want to use read-writer lock between processes , i need to transfer pthread_rwlock_t mem_lock to child process, i have a simple code , how can i trasfer the handle . i dont want to use a mutex.

rwlock1(parent)’s code

#include <unistd.h>
#include <pthread.h>
#include <sys/wait.h>

pthread_rwlock_t mem_lock;

int main() {
   pid_t pid;

   //init attr
   pthread_rwlockattr_t mem_lock_attr;
   pthread_rwlockattr_init(&mem_lock_attr);
   pthread_rwlockattr_setpshared(&mem_lock_attr, 1);

   //init read writer lock
   pthread_rwlock_init(&mem_lock, &mem_lock_attr);

   pid = fork();
   if (pid == 0) {
       execl("rwlock2", "rwlock2", (char *) nullptr);
   }

   //wait child
   wait(nullptr);

   return 0;
}

Answer

I haven’t tried, but it looks like this can be done if you put the lock in shared memory (e.g. set up by mmap or shmget) and use pthread_rwlockattr_setpshared to set the lock as process-shared.

See also 2.9.9 Synchronization Object Copies and Alternative Mappings in IEEE Std 1003.1-2017.