fdev: Improve fdev handling with epoll

Change-Id: I53c6eb394772e40f87000a0e5383be923f5d15f1
Signed-off-by: José Bollo <jose.bollo@iot.bzh>

5 files changed, 74 insertions, 16 deletions

diff --git a/src/fdev-epoll.c b/src/fdev-epoll.c
index 80c037d0..5043440c 100644
--- a/src/fdev-epoll.c
+++ b/src/fdev-epoll.c
@@ -23,15 +23,30 @@
 #include "fdev.h"
 #include "fdev-epoll.h"
 
+/*
+ * For sake of simplicity there is no struct fdev_epoll.
+ * Instead, the file descriptor of the internal epoll is used
+ * and wrapped in a pseudo pointer to a pseudo struct.
+ */
 #define epollfd(fdev_epoll)  ((int)(intptr_t)fdev_epoll)
 
+/*
+ * disable callback for fdev
+ *
+ * refs to fdev must not be counted here
+ */
 static void disable(void *closure, const struct fdev *fdev)
 {
 	struct fdev_epoll *fdev_epoll = closure;
 	epoll_ctl(epollfd(fdev_epoll), EPOLL_CTL_DEL, fdev_fd(fdev), 0);
 }
 
-static void enable(void *closure, const struct fdev *fdev)
+/*
+ * enable callback for fdev
+ *
+ * refs to fdev must not be counted here
+ */
+static void enable_or_update(void *closure, const struct fdev *fdev, int op, int err)
 {
 	struct fdev_epoll *fdev_epoll = closure;
 	struct epoll_event event;
@@ -40,18 +55,45 @@ static void enable(void *closure, const struct fdev *fdev)
 	fd = fdev_fd(fdev);
 	event.events = fdev_events(fdev);
 	event.data.ptr = (void*)fdev;
-	rc = epoll_ctl(epollfd(fdev_epoll), EPOLL_CTL_MOD, fd, &event);
-	if (rc < 0 && errno == ENOENT)
-		epoll_ctl(epollfd(fdev_epoll), EPOLL_CTL_ADD, fd, &event);
+	rc = epoll_ctl(epollfd(fdev_epoll), op, fd, &event);
+	if (rc < 0 && errno == err)
+		epoll_ctl(epollfd(fdev_epoll), (EPOLL_CTL_MOD + EPOLL_CTL_ADD) - op, fd, &event);
+}
+
+/*
+ * enable callback for fdev
+ *
+ * refs to fdev must not be counted here
+ */
+static void enable(void *closure, const struct fdev *fdev)
+{
+	enable_or_update(closure, fdev, EPOLL_CTL_ADD, EEXIST);
+}
+
+/*
+ * update callback for fdev
+ *
+ * refs to fdev must not be counted here
+ */
+static void update(void *closure, const struct fdev *fdev)
+{
+	enable_or_update(closure, fdev, EPOLL_CTL_MOD, ENOENT);
 }
 
+/*
+ * unref is not handled here
+ */
 static struct fdev_itf itf =
 {
 	.unref = 0,
 	.disable = disable,
-	.enable = enable
+	.enable = enable,
+	.update = update
 };
 
+/*
+ * create an fdev_epoll
+ */
 struct fdev_epoll *fdev_epoll_create()
 {
 	int fd = epoll_create1(EPOLL_CLOEXEC);
@@ -62,16 +104,25 @@ struct fdev_epoll *fdev_epoll_create()
 	return fd < 0 ? 0 : (struct fdev_epoll*)(intptr_t)fd;
 }
 
+/*
+ * destroy the fdev_epoll
+ */
 void fdev_epoll_destroy(struct fdev_epoll *fdev_epoll)
 {
 	close(epollfd(fdev_epoll));
 }
 
+/*
+ * get pollable fd for the fdev_epoll
+ */
 int fdev_epoll_fd(struct fdev_epoll *fdev_epoll)
 {
 	return epollfd(fdev_epoll);
 }
 
+/*
+ * create an fdev linked to the 'fdev_epoll' for 'fd'
+ */
 struct fdev *fdev_epoll_add(struct fdev_epoll *fdev_epoll, int fd)
 {
 	struct fdev *fdev;
@@ -82,16 +133,20 @@ struct fdev *fdev_epoll_add(struct fdev_epoll *fdev_epoll, int fd)
 	return fdev;
 }
 
-void fdev_epoll_wait_and_dispatch(struct fdev_epoll *fdev_epoll, int timeout_ms)
+/*
+ * get pollable fd for the fdev_epoll
+ */
+int fdev_epoll_wait_and_dispatch(struct fdev_epoll *fdev_epoll, int timeout_ms)
 {
 	struct fdev *fdev;
-	struct epoll_event events[8];
-	int rc, i;
+	struct epoll_event events;
+	int rc;
 
-	rc = epoll_wait(epollfd(fdev_epoll), events, sizeof events / sizeof *events, timeout_ms < 0 ? -1 : timeout_ms);
-	for (i = 0 ; i < rc ; i++) {
-		fdev = events[i].data.ptr;
-		fdev_dispatch(fdev, events[i].events);
+	rc = epoll_wait(epollfd(fdev_epoll), &events, 1, timeout_ms < 0 ? -1 : timeout_ms);
+	if (rc == 1) {
+		fdev = events.data.ptr;
+		fdev_dispatch(fdev, events.events);
 	}
+	return rc;
 }
 
diff --git a/src/fdev-epoll.h b/src/fdev-epoll.h
index 53d02e72..4b81f86e 100644
--- a/src/fdev-epoll.h
+++ b/src/fdev-epoll.h
@@ -24,5 +24,5 @@ extern struct fdev_epoll *fdev_epoll_create();
 extern void fdev_epoll_destroy(struct fdev_epoll *fdev_epoll);
 extern int fdev_epoll_fd(struct fdev_epoll *fdev_epoll);
 extern struct fdev *fdev_epoll_add(struct fdev_epoll *fdev_epoll, int fd);
-extern void fdev_epoll_wait_and_dispatch(struct fdev_epoll *fdev_epoll, int timeout_ms);
+extern int fdev_epoll_wait_and_dispatch(struct fdev_epoll *fdev_epoll, int timeout_ms);
 
diff --git a/src/fdev-systemd.c b/src/fdev-systemd.c
index 0f4a03cd..9115dd0d 100644
--- a/src/fdev-systemd.c
+++ b/src/fdev-systemd.c
@@ -53,7 +53,8 @@ static struct fdev_itf itf =
 {
 	.unref = unref,
 	.disable = disable,
-	.enable = enable
+	.enable = enable,
+	.update = enable
 };
 
 struct fdev *fdev_systemd_create(struct sd_event *eloop, int fd)
diff --git a/src/fdev.c b/src/fdev.c
index 8ad79b5f..a8f36956 100644
--- a/src/fdev.c
+++ b/src/fdev.c
@@ -76,7 +76,8 @@ void fdev_unref(struct fdev *fdev)
 	if (fdev && __atomic_sub_fetch(&fdev->refcount, 2, __ATOMIC_RELAXED) <= 1) {
 		if (fdev->itf) {
 			fdev->itf->disable(fdev->closure_itf, fdev);
-			fdev->itf->unref(fdev->closure_itf);
+			if (fdev->itf->unref)
+				fdev->itf->unref(fdev->closure_itf);
 		}
 		if (fdev->refcount)
 			close(fdev->fd);
@@ -135,7 +136,7 @@ void fdev_set_events(struct fdev *fdev, uint32_t events)
 	if (events != fdev->events) {
 		fdev->events = events;
 		if (is_active(fdev))
-			fdev->itf->enable(fdev->closure_itf, fdev);
+			fdev->itf->update(fdev->closure_itf, fdev);
 	}
 }
 
diff --git a/src/fdev.h b/src/fdev.h
index 9fbcb759..1e2f49f6 100644
--- a/src/fdev.h
+++ b/src/fdev.h
@@ -27,6 +27,7 @@ struct fdev_itf
 	void (*unref)(void *closure);
 	void (*disable)(void *closure, const struct fdev *fdev);
 	void (*enable)(void *closure, const struct fdev *fdev);
+	void (*update)(void *closure, const struct fdev *fdev);
 };
 
 extern struct fdev *fdev_create(int fd);