问题
I'm porting a Windows application to Linux and I have a synchronization problem.
In Windows I'm using a system-level named mutex to sync access to a shared memory block.
How do I emulate that in Linux? I've created a SystemV semaphore, using semget. The problem is that it is not reentrant, if I already hold it it will block, unlike on Windows. I could add a reference count to it, but then I would need to synchronize access to that, which means another (this time for the current process only) mutex.
Is there a class somewhere which provides a reentrant interprocess lock (maybe in Boost)?
BTW, using a file lock is not acceptable since it will probably be too slow (I need ultra-low latency communication between the two processes).
回答1:
You can just use a shared (interprocess), recursive pthread_mutex_t. Create a normal pthread_mutex (stored in shared memory) and set its attributes using pthread_mutexattr_settype with the PTHREAD_MUTEX_RECURSIVE flag, and then call pthread_mutexattr_setpshared with the PTHREAD_MUTEX_SHARED flag.
That will give you a reentrant, interprocess lock.
回答2:
You could try building your own out of futexes. See usersem.c in this tarball.
来源：https://stackoverflow.com/questions/1748902/linux-inter-process-reentrant-semaphore