diff options
| -rw-r--r-- | src/simple_semaphore.hpp | 60 |
1 files changed, 57 insertions, 3 deletions
diff --git a/src/simple_semaphore.hpp b/src/simple_semaphore.hpp index 209ccb4..3342281 100644 --- a/src/simple_semaphore.hpp +++ b/src/simple_semaphore.hpp @@ -23,7 +23,11 @@ #include "platform.hpp" #include "err.hpp" -#if defined ZMQ_HAVE_LINUX || defined ZMQ_HAVE_OSX || defined ZMQ_HAVE_OPENVMS +#if 0 //defined ZMQ_HAVE_LINUX +#include <sys/syscall.h> +#include <unistd.h> +#include <linux/futex.h> +#elif defined ZMQ_HAVE_LINUX ||defined ZMQ_HAVE_OSX || defined ZMQ_HAVE_OPENVMS #include <pthread.h> #elif defined ZMQ_HAVE_WINDOWS #include "windows.hpp" @@ -33,13 +37,63 @@ namespace zmq { - // Simple semaphore. Only single thread may be waiting at any given time. // Also, the semaphore may not be posted before the previous post // was matched by corresponding wait and the waiting thread was // released. -#if defined ZMQ_HAVE_LINUX || defined ZMQ_HAVE_OSX || defined ZMQ_HAVE_OPENVMS +#if 0 //defined ZMQ_HAVE_LINUX + + // In theory, using private futexes should be more efficient on Linux + // platform than using mutexes. However, in uncontended cases of TCP + // transport on loopback interface we haven't seen any latency improvement. + // The code is commented out waiting for more thorough testing. + + class simple_semaphore_t + { + public: + + // Initialise the semaphore. + inline simple_semaphore_t () : + dummy (0) + { + } + + // Destroy the semaphore. + inline ~simple_semaphore_t () + { + } + + // Wait for the semaphore. + inline void wait () + { + int rc = syscall (SYS_futex, &dummy, (int) FUTEX_WAIT_PRIVATE, + (int) 0, NULL, NULL, (int) 0); + zmq_assert (rc == 0); + } + + // Post the semaphore. + inline void post () + { + while (true) { + int rc = syscall (SYS_futex, &dummy, (int) FUTEX_WAKE_PRIVATE, + (int) 1, NULL, NULL, (int) 0); + zmq_assert (rc != -1 && rc <= 1); + if (rc == 1) + break; + } + } + + private: + + int dummy; + + // Disable copying of the object. + simple_semaphore_t (const simple_semaphore_t&); + void operator = (const simple_semaphore_t&); + }; + +#elif defined ZMQ_HAVE_LINUX || defined ZMQ_HAVE_OSX || defined ZMQ_HAVE_OPENVMS // On platforms that allow for double locking of a mutex from the same // thread, simple semaphore is implemented using mutex, as it is more |