Fast interprocess synchronization method

I have a chunk of shared memory containing some data. Reading / writing this data needs to be synchronized b开发者_运维百科etween different processes. At this moment I'm using unnamed POSIX semaphores. Since my main concern is speed, I'd like to know if semaphores are optimal here? Do they end with a syscall for example (userspace -> kernel space), or force context switches? What would you suggest?

Some info on unnamed semaphores: http://linux.die.net/man/3/sem_init

Since distinct processes have distinct address spaces, any synchronization feature will have to go through the kernel... except if you manage to synchronize through a chunk of shared memory. And you so happen to have such a chunk.

Therefore, I recommend using a pthreads mutex (see pthread_mutex_lock()) located at some place within your chunk of shared memory. This will work on a recent enough Linux system (glibc-2.3.2 or later, kernel 2.6.x). With a mutex, the kernel will be invoked only upon contention (two processes competing for the same lock), in which case going through the kernel is the right thing to do.