1 files changed, 62 insertions, 24 deletions

diff --git a/src/wg.c b/src/wg.c
index c326f53..4e673b4 100644
--- a/src/wg.c
+++ b/src/wg.c
@@ -26,37 +26,75 @@
 
 /* pthread_cond_t is overly complicated. Just use a self-pipe. */
 
+static
+void *wg_gc(void *wg_anon) {
+	struct wg *wg = wg_anon;
+
+	pthread_t thread;
+	while (1) {
+		ssize_t r = read(wg->fd_threads[0], &thread, sizeof(thread));
+		if (r < 0) {
+			if (errno == EINTR)
+				continue;
+			error(EXIT_FAILURE, errno, "wg_gc: read");
+		} else if ((size_t)r < sizeof(thread)) {
+			error(EXIT_FAILURE, 0, "wg_gc: read: only read %zd/%zu", r, sizeof(thread));
+		}
+
+		pthread_join(thread, NULL);
+
+		int p;
+		if ((p = pthread_mutex_lock(&wg->lock)) != 0)
+			error(EXIT_FAILURE, p, "wg_gc: pthread_mutex_lock");
+		wg->count--;
+		if (wg->count == 0) {
+			if ((p = pthread_mutex_unlock(&wg->lock)) != 0)
+				error(EXIT_FAILURE, p, "wg_gc: pthread_mutex_unlock");
+			return NULL;
+		}
+		if ((p = pthread_mutex_unlock(&wg->lock)) != 0)
+			error(EXIT_FAILURE, p, "wg_gc: pthread_mutex_unlock");
+	}
+}
+
 void wg_init(struct wg *wg) {
 	wg->count = 0;
-	pthread_mutex_init(&wg->lock, NULL);
-	int fds[2];
-	if (pipe(fds) != 0)
-		error(EXIT_FAILURE, errno, "pipe");
-	wg->fd_wait = fds[0];
-	wg->fd_signal = fds[1];
+	int r;
+	if ((r = pthread_mutex_init(&wg->lock, NULL)) != 0)
+		error(EXIT_FAILURE, r, "wg_init: pthread_mutex_init");
+	if (pipe(wg->fd_threads) != 0)
+		error(EXIT_FAILURE, errno, "wg_init: pipe");
+	if ((r = pthread_create(&wg->gc, NULL, wg_gc, (void*)wg)) != 0)
+		error(EXIT_FAILURE, r, "wg_init: pthread_create");
 }
 
-void wg_add(struct wg *wg, unsigned int n) {
-	pthread_mutex_lock(&wg->lock);
-	wg->count += n;
-	pthread_mutex_unlock(&wg->lock);
+void wg_add(struct wg *wg) {
+	int r;
+	if ((r = pthread_mutex_lock(&wg->lock)) != 0)
+		error(EXIT_FAILURE, r, "wg_add: pthread_mutex_lock");
+	wg->count++;
+	if ((r = pthread_mutex_unlock(&wg->lock)) != 0)
+		error(EXIT_FAILURE, r, "wg_add: pthread_mutex_unlock");
 }
 
-void wg_sub(struct wg *wg, unsigned int n) {
-	pthread_mutex_lock(&wg->lock);
-	wg->count -= n;
-	if (wg->count == 0)
-		if (write(wg->fd_signal, " ", 1) < 1)
-			error(EXIT_FAILURE, errno, "write");
-	pthread_mutex_unlock(&wg->lock);
+void wg_sub(struct wg *wg) {
+	pthread_t thread = pthread_self();
+	ssize_t r = write(wg->fd_threads[1], &thread, sizeof(thread));
+	if (r < 0) {
+		error(EXIT_FAILURE, errno, "wg_sub: write");
+	} else if ((size_t)r < sizeof(thread)) {
+		error(EXIT_FAILURE, 0, "wg_sub: only wrote %zd/%zu", r, sizeof(thread));
+	}
 }
 
 void wg_wait(struct wg *wg) {
-	char b;
- retry:
-	if (read(wg->fd_wait, &b, 1) == -1) {
-		if (errno == EINTR)
-			goto retry;
-		error(EXIT_FAILURE, errno, "wg_wait");
-	}
+	int r;
+	if ((r = pthread_join(wg->gc, NULL)) != 0)
+		error(EXIT_FAILURE, r, "wg_wait: pthread_join");
+	if (close(wg->fd_threads[1]) != 0)
+		error(EXIT_FAILURE, errno, "wg_wait: close(fd_threads[1])");
+	if (close(wg->fd_threads[0]) != 0)
+		error(EXIT_FAILURE, errno, "wg_wait: close(fd_threads[0])");
+	if ((r = pthread_mutex_destroy(&wg->lock)) != 0)
+		error(EXIT_FAILURE, r, "wg_wait: pthread_mutex_destroy");
 }