kqueue并可kevent用于此目的。OSX 10.6 和 FreeBSD 8.1 添加了对 的支持EVFILT_USER，我们可以用它来从另一个线程唤醒事件循环。
请注意，如果您使用它来实现自己的条件和定时等待，则不需要锁来避免竞争条件，这与这个出色的答案相反，因为您不能“错过”队列中的事件。
资料来源：
示例代码
编译clang -o test -std=c99 test.c
#include <sys/types.h>
#include <sys/event.h>
#include <sys/time.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <pthread.h>
// arbitrary number used for the identifier property
const int NOTIFY_IDENT = 1337;
static int kq;
static void diep(const char *s) {
perror(s);
exit(EXIT_FAILURE);
}
static void *run_thread(void *arg) {
struct kevent kev;
struct kevent out_kev;
memset(&kev, 0, sizeof(kev));
kev.ident = NOTIFY_IDENT;
kev.filter = EVFILT_USER;
kev.flags = EV_ADD | EV_CLEAR;
struct timespec timeout;
timeout.tv_sec = 3;
timeout.tv_nsec = 0;
fprintf(stderr, "thread sleep\n");
if (kevent(kq, &kev, 1, &out_kev, 1, &timeout) == -1)
diep("kevent: waiting");
fprintf(stderr, "thread wakeup\n");
return NULL;
}
int main(int argc, char **argv) {
// create a new kernel event queue
kq = kqueue();
if (kq == -1)
diep("kqueue()");
fprintf(stderr, "spawn thread\n");
pthread_t thread;
if (pthread_create(&thread, NULL, run_thread, NULL))
diep("pthread_create");
if (argc > 1) {
fprintf(stderr, "sleep for 1 second\n");
sleep(1);
fprintf(stderr, "wake up thread\n");
struct kevent kev;
struct timespec timeout = { 0, 0 };
memset(&kev, 0, sizeof(kev));
kev.ident = NOTIFY_IDENT;
kev.filter = EVFILT_USER;
kev.fflags = NOTE_TRIGGER;
if (kevent(kq, &kev, 1, NULL, 0, &timeout) == -1)
diep("kevent: triggering");
} else {
fprintf(stderr, "not waking up thread, pass --wakeup to wake up thread\n");
}
pthread_join(thread, NULL);
close(kq);
return EXIT_SUCCESS;
}
输出
$ time ./test
spawn thread
not waking up thread, pass --wakeup to wake up thread
thread sleep
thread wakeup
real 0m3.010s
user 0m0.001s
sys 0m0.002s
$ time ./test --wakeup
spawn thread
sleep for 1 second
thread sleep
wake up thread
thread wakeup
real 0m1.010s
user 0m0.002s
sys 0m0.002s