st/oxr: Protoct event queue with a mutex

doc/changes/state_trackers/mr.359.4.md

@@ -0,0 +1,2 @@
+OpenXR: Make the event queue thread safe, all done with a simple mutex that is
+not held for long at all.

src/xrt/state_trackers/oxr/oxr_event.c

@@ -7,17 +7,24 @@
  * @ingroup oxr_main
  */
 
-#include <stdio.h>
-#include <string.h>
-#include <stdlib.h>
+#include "os/os_threading.h"
 
 #include "util/u_misc.h"
 
 #include "oxr_objects.h"
 #include "oxr_logger.h"
 
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
 
 
+/*
+ *
+ * Struct and defines.
+ *
+ */
+
 struct oxr_event
 {
 	struct oxr_event *next;
@@ -26,13 +33,23 @@ struct oxr_event
 };
 
 
+/*
+ *
+ * Internal helpers.
+ *
+ */
+
 void
 lock(struct oxr_instance *inst)
-{}
+{
+	os_mutex_lock(&inst->event.mutex);
+}
 
 void
 unlock(struct oxr_instance *inst)
-{}
+{
+	os_mutex_unlock(&inst->event.mutex);
+}
 
 void *
 oxr_event_extra(struct oxr_event *event)
@@ -43,16 +60,16 @@ oxr_event_extra(struct oxr_event *event)
 struct oxr_event *
 pop(struct oxr_instance *inst)
 {
-	struct oxr_event *ret = inst->next_event;
+	struct oxr_event *ret = inst->event.next;
 	if (ret == NULL) {
 		return NULL;
 	}
 
-	inst->next_event = ret->next;
+	inst->event.next = ret->next;
 	ret->next = NULL;
 
-	if (ret == inst->last_event) {
-		inst->last_event = NULL;
+	if (ret == inst->event.last) {
+		inst->event.last = NULL;
 	}
 
 	return ret;
@@ -61,14 +78,14 @@ pop(struct oxr_instance *inst)
 void
 push(struct oxr_instance *inst, struct oxr_event *event)
 {
-	struct oxr_event *last = inst->last_event;
+	struct oxr_event *last = inst->event.last;
 	if (last != NULL) {
 		last->next = event;
 	}
-	inst->last_event = event;
+	inst->event.last = event;
 
-	if (inst->next_event == NULL) {
-		inst->next_event = event;
+	if (inst->event.next == NULL) {
+		inst->event.next = event;
 	}
 }
 
@@ -105,6 +122,13 @@ oxr_event_alloc(struct oxr_logger *log,
 	return XR_SUCCESS;
 }
 
+
+/*
+ *
+ * 'Exported' functions.
+ *
+ */
+
 XrResult
 oxr_event_push_XrEventDataSessionStateChanged(struct oxr_logger *log,
                                               struct oxr_session *sess,
@@ -142,7 +166,7 @@ oxr_event_remove_session_events(struct oxr_logger *log,
 
 	lock(inst);
 
-	struct oxr_event *e = inst->next_event;
+	struct oxr_event *e = inst->event.next;
 	while (e != NULL) {
 		struct oxr_event *cur = e;
 		e = e->next;
@@ -156,12 +180,12 @@ oxr_event_remove_session_events(struct oxr_logger *log,
 			continue;
 		}
 
-		if (cur == inst->next_event) {
-			inst->next_event = cur->next;
+		if (cur == inst->event.next) {
+			inst->event.next = cur->next;
 		}
 
-		if (cur == inst->last_event) {
-			inst->last_event = NULL;
+		if (cur == inst->event.last) {
+			inst->event.last = NULL;
 		}
 		free(cur);
 	}

src/xrt/state_trackers/oxr/oxr_instance.c

@@ -76,6 +76,9 @@ oxr_instance_destroy(struct oxr_logger *log, struct oxr_handle_base *hb)
 	// Does null checking and sets to null.
 	time_state_destroy(&inst->timekeeping);
 
+	// Mutex goes last.
+	os_mutex_destroy(&inst->event.mutex);
+
 	free(inst);
 
 	return XR_SUCCESS;
@@ -99,7 +102,7 @@ oxr_instance_create(struct oxr_logger *log,
 {
 	struct oxr_instance *inst = NULL;
 	struct xrt_device *xdevs[NUM_XDEVS] = {0};
-	int xinst_ret;
+	int xinst_ret, m_ret;
 	XrResult ret;
 
 	OXR_ALLOCATE_HANDLE_OR_RETURN(log, inst, OXR_XR_DEBUG_INSTANCE,
@@ -110,14 +113,20 @@ oxr_instance_create(struct oxr_logger *log,
 	inst->debug_views = debug_get_bool_option_debug_views();
 	inst->debug_bindings = debug_get_bool_option_debug_bindings();
 
+	m_ret = os_mutex_init(&inst->event.mutex);
+	if (m_ret < 0) {
+		ret = oxr_error(log, XR_ERROR_RUNTIME_FAILURE,
+		                "Failed to init mutex");
+		return ret;
+	}
+
 	/* ---- HACK ---- */
 	oxr_sdl2_hack_create(&inst->hack);
 	/* ---- HACK ---- */
 
 	ret = oxr_path_init(log, inst);
 	if (ret != XR_SUCCESS) {
-		free(inst);
-		return 0;
+		return ret;
 	}
 
 	// Cache certain often looked up paths.

src/xrt/state_trackers/oxr/oxr_objects.h

@@ -14,11 +14,15 @@
 #include "xrt/xrt_compositor.h"
 #include "xrt/xrt_vulkan_includes.h"
 #include "xrt/xrt_openxr_includes.h"
+
+#include "os/os_threading.h"
+
 #include "util/u_hashset.h"
 #include "util/u_hashmap.h"
 
 #include "oxr_extension_support.h"
 
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -965,8 +969,12 @@ struct oxr_instance
 	size_t path_num;
 
 	// Event queue.
-	struct oxr_event *last_event;
-	struct oxr_event *next_event;
+	struct
+	{
+		struct os_mutex mutex;
+		struct oxr_event *last;
+		struct oxr_event *next;
+	} event;
 
 	struct oxr_interaction_profile **profiles;
 	size_t num_profiles;