如何定义自己的线程函数与第三方系统兼容

在多线程的环境中，我们需要有线程创建函数来创建需要的线程，一般的系统都是有自己的线程创建函数的，但是有的系统没有，或者说两个系统不兼容，那么我们就需要有自己的线程创建函数来兼容第三方，一般在模拟线程创建的时候都是用进程来实现的，下面就是一个例子：

static int
pthread_create(sp_pthread_t *thread, const void *attr,
    void *(*thread_start)(void *), void *arg)
{
	pid_t pid;
	struct pam_ctxt *ctx = arg;

	sshpam_thread_status = -1;
	switch ((pid = fork())) {
	case -1:
		error("fork(): %s", strerror(errno));
		return (-1);
	case 0:
		close(ctx->pam_psock);
		ctx->pam_psock = -1;
		thread_start(arg);
		_exit(1);
	default:
		*thread = pid;
		close(ctx->pam_csock);
		ctx->pam_csock = -1;
		sshpam_oldsig = signal(SIGCHLD, sshpam_sigchld_handler);
		return (0);
	}
}

typedef pthread_t sp_pthread_t;
#else
typedef pid_t sp_pthread_t;
#endif

struct pam_ctxt {
	sp_pthread_t	 pam_thread;
	int		 pam_psock;
	int		 pam_csock;
	int		 pam_done;
};

static void sshpam_free_ctx(void *);
static struct pam_ctxt *cleanup_ctxt;

#ifndef UNSUPPORTED_POSIX_THREADS_HACK
/*
 * Simulate threads with processes.
 */

static int sshpam_thread_status = -1;
static mysig_t sshpam_oldsig;

static void
sshpam_sigchld_handler(int sig)
{
	signal(SIGCHLD, SIG_DFL);
	if (cleanup_ctxt == NULL)
		return;	/* handler called after PAM cleanup, shouldn't happen */
	if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, WNOHANG)
	    <= 0) {
		/* PAM thread has not exitted, privsep slave must have */
		kill(cleanup_ctxt->pam_thread, SIGTERM);
		if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, 0)
		    <= 0)
			return; /* could not wait */
	}
	if (WIFSIGNALED(sshpam_thread_status) &&
	    WTERMSIG(sshpam_thread_status) == SIGTERM)
		return;	/* terminated by pthread_cancel */
	if (!WIFEXITED(sshpam_thread_status))
		sigdie("PAM: authentication thread exited unexpectedly");
	if (WEXITSTATUS(sshpam_thread_status) != 0)
		sigdie("PAM: authentication thread exited uncleanly");
}

/* ARGSUSED */
static void
pthread_exit(void *value)
{
	_exit(0);
}

版权声明：本文为博主原创文章，未经博主允许不得转载。