Initial version.

src/nxt_semaphore.c

@@ -0,0 +1,244 @@
+
+/*
+ * Copyright (C) Igor Sysoev
+ * Copyright (C) NGINX, Inc.
+ */
+
+#include <nxt_main.h>
+
+
+#if (NXT_HAVE_SEM_TIMEDWAIT)
+
+/*
+ * Linux POSIX semaphores use atomic/futex operations in since glibc 2.3.
+ *
+ * FreeBSD has two POSIX semaphore implementations.  The first implementation
+ * has been introduced in FreeBSD 5.0 but it has some drawbacks:
+ *   1) it had a bug (http://bugs.freebsd.org/127545) fixed in FreeBSD 7.2;
+ *   2) it does not use atomic operations and always calls ksem syscalls;
+ *   3) a number of semaphores is just 30 by default and until FreeBSD 8.1
+ *      the number cannot be changed after boot time.
+ *
+ * The second implementation has been introduced in FreeBSD 6.1 in libthr
+ * and uses atomic operations and umtx syscall.  However, until FreeBSD 9.0
+ * a choice of implementation depended on linking order of libthr and libc.
+ * In FreeBSD 9.0 the umtx implementation has been moved to libc.
+ *
+ * Solaris have POSIX semaphores.
+ *
+ * MacOSX has limited POSIX semaphore implementation:
+ *  1) sem_init() exists but returns ENOSYS;
+ *  2) no sem_timedwait().
+ */
+
+nxt_int_t
+nxt_sem_init(nxt_sem_t *sem, nxt_uint_t count)
+{
+    if (sem_init(sem, 0, count) == 0) {
+        nxt_thread_log_debug("sem_init(%p)", sem);
+        return NXT_OK;
+    }
+
+    nxt_thread_log_alert("sem_init(%p) failed %E", sem, nxt_errno);
+    return NXT_ERROR;
+}
+
+
+void
+nxt_sem_destroy(nxt_sem_t *sem)
+{
+    if (sem_destroy(sem) == 0) {
+        nxt_thread_log_debug("sem_destroy(%p)", sem);
+        return;
+    }
+
+    nxt_thread_log_alert("sem_destroy(%p) failed %E", sem, nxt_errno);
+}
+
+
+nxt_int_t
+nxt_sem_post(nxt_sem_t *sem)
+{
+    nxt_thread_log_debug("sem_post(%p)", sem);
+
+    if (nxt_fast_path(sem_post(sem) == 0)) {
+        return NXT_OK;
+    }
+
+    nxt_thread_log_alert("sem_post(%p) failed %E", sem, nxt_errno);
+
+    return NXT_ERROR;
+}
+
+
+nxt_err_t
+nxt_sem_wait(nxt_sem_t *sem, nxt_nsec_t timeout)
+{
+    int              n;
+    nxt_err_t        err;
+    nxt_nsec_t       ns;
+    nxt_thread_t     *thr;
+    nxt_realtime_t   *now;
+    struct timespec  ts;
+
+    thr = nxt_thread();
+
+    if (timeout == NXT_INFINITE_NSEC) {
+        nxt_log_debug(thr->log, "sem_wait(%p) enter", sem);
+
+        for ( ;; ) {
+            n = sem_wait(sem);
+
+            err = nxt_errno;
+
+            nxt_thread_time_update(thr);
+
+            if (nxt_fast_path(n == 0)) {
+                nxt_thread_log_debug("sem_wait(%p) exit", sem);
+                return 0;
+            }
+
+            switch (err) {
+
+            case NXT_EINTR:
+                nxt_log_error(NXT_LOG_INFO, thr->log, "sem_wait(%p) failed %E",
+                              sem, err);
+                continue;
+
+            default:
+                nxt_log_alert(thr->log, "sem_wait(%p) failed %E", sem, err);
+                return err;
+            }
+        }
+    }
+
+#if (NXT_HAVE_SEM_TRYWAIT_FAST)
+
+    nxt_log_debug(thr->log, "sem_trywait(%p) enter", sem);
+
+    /*
+     * Fast sem_trywait() using atomic operations may eliminate
+     * timeout processing.
+     */
+
+    if (nxt_fast_path(sem_trywait(sem) == 0)) {
+        return 0;
+    }
+
+#endif
+
+    nxt_log_debug(thr->log, "sem_timedwait(%p, %N) enter", sem, timeout);
+
+    now = nxt_thread_realtime(thr);
+    ns = now->nsec + timeout;
+    ts.tv_sec = now->sec + ns / 1000000000;
+    ts.tv_nsec = ns % 1000000000;
+
+    for ( ;; ) {
+        n = sem_timedwait(sem, &ts);
+
+        err = nxt_errno;
+
+        nxt_thread_time_update(thr);
+
+        if (nxt_fast_path(n == 0)) {
+            nxt_thread_log_debug("sem_timedwait(%p) exit", sem);
+            return 0;
+        }
+
+        switch (err) {
+
+        case NXT_ETIMEDOUT:
+            nxt_log_debug(thr->log, "sem_timedwait(%p) exit: %d", sem, err);
+            return err;
+
+        case NXT_EINTR:
+            nxt_log_error(NXT_LOG_INFO, thr->log, "sem_timedwait(%p) failed %E",
+                          sem, err);
+            continue;
+
+        default:
+            nxt_log_alert(thr->log, "sem_timedwait(%p) failed %E", sem, err);
+            return err;
+        }
+    }
+}
+
+#else
+
+/* Semaphore implementation using pthread conditional variable. */
+
+nxt_int_t
+nxt_sem_init(nxt_sem_t *sem, nxt_uint_t count)
+{
+    if (nxt_thread_mutex_create(&sem->mutex) == NXT_OK) {
+
+        if (nxt_thread_cond_create(&sem->cond) == NXT_OK) {
+            sem->count = count;
+            return NXT_OK;
+        }
+
+        nxt_thread_mutex_destroy(&sem->mutex);
+    }
+
+    return NXT_ERROR;
+}
+
+
+void
+nxt_sem_destroy(nxt_sem_t *sem)
+{
+    nxt_thread_cond_destroy(&sem->cond);
+    nxt_thread_mutex_destroy(&sem->mutex);
+}
+
+
+nxt_int_t
+nxt_sem_post(nxt_sem_t *sem)
+{
+    nxt_int_t  ret;
+
+    if (nxt_slow_path(nxt_thread_mutex_lock(&sem->mutex) != NXT_OK)) {
+        return NXT_ERROR;
+    }
+
+    ret = nxt_thread_cond_signal(&sem->cond);
+
+    sem->count++;
+
+    /* NXT_ERROR overrides NXT_OK. */
+
+    return (nxt_thread_mutex_unlock(&sem->mutex) | ret);
+}
+
+
+nxt_err_t
+nxt_sem_wait(nxt_sem_t *sem, nxt_nsec_t timeout)
+{
+    nxt_err_t  err;
+
+    err = 0;
+
+    if (nxt_slow_path(nxt_thread_mutex_lock(&sem->mutex) != NXT_OK)) {
+        return NXT_ERROR;
+    }
+
+    while (sem->count == 0) {
+
+        err = nxt_thread_cond_wait(&sem->cond, &sem->mutex, timeout);
+
+        if (err != 0) {
+            goto error;
+        }
+    }
+
+    sem->count--;
+
+error:
+
+    /* NXT_ERROR overrides NXT_OK and NXT_ETIMEDOUT. */
+
+    return (nxt_thread_mutex_unlock(&sem->mutex) | err);
+}
+
+#endif