Free old lease fd reference after transition

After a lease is tranisitined to a new client, the reference to
the previous client's lease fd is no longer needed and should
be released.

Close the old fd after the new client has either updated the
display or its lease is revoked.

Bug-AGL: SPEC-3816

Change-Id: I9612913e2960dce94bcfc6a35c0105a5670a453d
Signed-off-by: Damian Hobson-Garcia <dhobsong@igel.co.jp>

3 files changed, 93 insertions, 4 deletions

diff --git a/drm-lease-manager/lease-manager.c b/drm-lease-manager/lease-manager.c
index 6fafb46..5d79b8d 100644
--- a/drm-lease-manager/lease-manager.c
+++ b/drm-lease-manager/lease-manager.c
@@ -22,6 +22,8 @@
 #include <assert.h>
 #include <errno.h>
 #include <fcntl.h>
+#include <poll.h>
+#include <pthread.h>
 #include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
@@ -47,6 +49,11 @@ struct lease {
 
 	uint32_t *object_ids;
 	int nobject_ids;
+
+	/* for lease transfer completion */
+	uint32_t crtc_id;
+	pthread_t transition_tid;
+	bool transition_running;
 };
 
 struct lm {
@@ -199,6 +206,87 @@ static bool lease_add_planes(struct lm *lm, struct lease *lease, int crtc_index)
 	return true;
 }
 
+/* Lease transition
+ * Wait for a client to update the DRM framebuffer on the CRTC managed by
+ * a lease.  Once the framebuffer has been updated, it is safe to close
+ * the fd associated with the previous lease client, freeing the previous
+ * framebuffer if there are no other references to it. */
+static void wait_for_fb_update(struct lease *lease, uint32_t old_fb)
+{
+	uint32_t current_fb = old_fb;
+
+	struct pollfd drm_poll = {
+	    .fd = lease->lease_fd,
+	    .events = POLLIN,
+	};
+
+	while (current_fb == old_fb) {
+		drmModeCrtcPtr crtc;
+		if (poll(&drm_poll, 1, -1) < 0) {
+			if (errno == EINTR)
+				continue;
+			break;
+		}
+
+		crtc = drmModeGetCrtc(lease->lease_fd, lease->crtc_id);
+		current_fb = crtc->buffer_id;
+		drmModeFreeCrtc(crtc);
+	}
+}
+
+struct transition_ctx {
+	struct lease *lease;
+	int close_fd;
+	uint32_t old_fb;
+};
+
+static void transition_done(void *arg)
+{
+	struct transition_ctx *ctx = arg;
+	close(ctx->close_fd);
+	free(ctx);
+}
+
+static void *finish_transition_task(void *arg)
+{
+	struct transition_ctx *ctx = arg;
+	pthread_cleanup_push(transition_done, ctx);
+	wait_for_fb_update(ctx->lease, ctx->old_fb);
+	pthread_cleanup_pop(true);
+	return NULL;
+}
+
+static void close_after_lease_transition(struct lease *lease, int close_fd)
+{
+	struct transition_ctx *ctx = calloc(1, sizeof(*ctx));
+
+	assert(ctx);
+
+	drmModeCrtcPtr crtc = drmModeGetCrtc(lease->lease_fd, lease->crtc_id);
+
+	ctx->lease = lease;
+	ctx->close_fd = close_fd;
+	ctx->old_fb = crtc->buffer_id;
+
+	drmModeFreeCrtc(crtc);
+
+	int ret = pthread_create(&lease->transition_tid, NULL,
+				 finish_transition_task, ctx);
+
+	lease->transition_running = (ret == 0);
+}
+
+static void cancel_lease_transition_thread(struct lease *lease)
+{
+
+	if (lease->transition_running) {
+		pthread_cancel(lease->transition_tid);
+		pthread_join(lease->transition_tid, NULL);
+	}
+
+	lease->transition_running = false;
+}
+
 static void lease_free(struct lease *lease)
 {
 	free(lease->base.name);
@@ -238,6 +326,7 @@ static struct lease *lease_create(struct lm *lm, drmModeConnectorPtr connector)
 		goto err;
 
 	uint32_t crtc_id = lm->drm_resource->crtcs[crtc_index];
+	lease->crtc_id = crtc_id;
 	lease->object_ids[lease->nobject_ids++] = crtc_id;
 	lease->object_ids[lease->nobject_ids++] = connector->connector_id;
 
@@ -381,8 +470,6 @@ int lm_lease_transfer(struct lm *lm, struct lease_handle *handle)
 	if (!lease->is_granted)
 		return -1;
 
-	// TODO: close this fd once a frame is presented from the new
-	//       client.
 	int old_lease_fd = dup(lease->lease_fd);
 
 	lm_lease_revoke(lm, handle);
@@ -391,6 +478,7 @@ int lm_lease_transfer(struct lm *lm, struct lease_handle *handle)
 		return -1;
 	}
 
+	close_after_lease_transition(lease, old_lease_fd);
 	return lease->lease_fd;
 }
 
@@ -405,6 +493,7 @@ void lm_lease_revoke(struct lm *lm, struct lease_handle *handle)
 		return;
 
 	drmModeRevokeLease(lm->drm_fd, lease->lessee_id);
+	cancel_lease_transition_thread(lease);
 	close(lease->lease_fd);
 	lease->is_granted = false;
 }
diff --git a/drm-lease-manager/meson.build b/drm-lease-manager/meson.build
index 1171b02..7157f01 100644
--- a/drm-lease-manager/meson.build
+++ b/drm-lease-manager/meson.build
@@ -3,7 +3,7 @@ lease_manager_files = files('lease-manager.c')
 lease_server_files = files('lease-server.c')
 main = executable('drm-lease-manager',
     [ 'main.c', lease_manager_files, lease_server_files ],
-    dependencies: [ drm_dep, dlmcommon_dep ],
+    dependencies: [ drm_dep, dlmcommon_dep, thread_dep ],
     install: true,
 )
 
diff --git a/meson.build b/meson.build
index 2f6cd15..7f8adf5 100644
--- a/meson.build
+++ b/meson.build
@@ -34,12 +34,12 @@ configure_file(output: 'config.h',
 configuration_inc = include_directories('.')
 
 drm_dep = dependency('libdrm', version: '>= 2.4.89')
+thread_dep = dependency('threads')
 
 enable_tests = get_option('enable-tests')
 
 if enable_tests
   check_dep = dependency('check')
-  thread_dep = dependency('threads')
 
 # Default to the system provided version of fff.h.
 # otherwise fetch it ourselves.