1#include <mqueue.h>
2#include <pthread.h>
3#include <errno.h>
4#include <sys/socket.h>
5#include <signal.h>
6#include <unistd.h>
7#include "syscall.h"
8
9struct args {
10	pthread_barrier_t barrier;
11	int sock;
12	const struct sigevent *sev;
13};
14
15static void *start(void *p)
16{
17	struct args *args = p;
18	char buf[32];
19	ssize_t n;
20	int s = args->sock;
21	void (*func)(union sigval) = args->sev->sigev_notify_function;
22	union sigval val = args->sev->sigev_value;
23
24	pthread_barrier_wait(&args->barrier);
25	n = recv(s, buf, sizeof(buf), MSG_NOSIGNAL|MSG_WAITALL);
26	close(s);
27	if (n==sizeof buf && buf[sizeof buf - 1] == 1)
28		func(val);
29	return 0;
30}
31
32int mq_notify(mqd_t mqd, const struct sigevent *sev)
33{
34	struct args args = { .sev = sev };
35	pthread_attr_t attr;
36	pthread_t td;
37	int s;
38	struct sigevent sev2;
39	static const char zeros[32];
40
41	if (!sev || sev->sigev_notify != SIGEV_THREAD)
42		return syscall(SYS_mq_notify, mqd, sev);
43
44	s = socket(AF_NETLINK, SOCK_RAW|SOCK_CLOEXEC, 0);
45	if (s < 0) return -1;
46	args.sock = s;
47
48	if (sev->sigev_notify_attributes) attr = *sev->sigev_notify_attributes;
49	else pthread_attr_init(&attr);
50	pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
51	pthread_barrier_init(&args.barrier, 0, 2);
52
53	if (pthread_create(&td, &attr, start, &args)) {
54		__syscall(SYS_close, s);
55		errno = EAGAIN;
56		return -1;
57	}
58
59	pthread_barrier_wait(&args.barrier);
60	pthread_barrier_destroy(&args.barrier);
61
62	sev2.sigev_notify = SIGEV_THREAD;
63	sev2.sigev_signo = s;
64	sev2.sigev_value.sival_ptr = (void *)&zeros;
65
66	if (syscall(SYS_mq_notify, mqd, &sev2) < 0) {
67		pthread_cancel(td);
68		__syscall(SYS_close, s);
69		return -1;
70	}
71
72	return 0;
73}
74