Fix #35960, #36044: blender internal viewport rendering crash while editing data.

Now the viewport rendering thread will lock the main thread while it is exporting
objects to render data. This is not ideal if you have big scenes that might block
the UI, but Cycles does the same, and it's fairly quick because the same evaluated
mesh can be used as for viewport drawing. It's the only way to get things stable
until the thread safe dependency graph is here.

This adds a mechanism to the job system for jobs to lock the main thread, using a
new 'ticket mutex lock' which is a mutex lock that gives priority to the first
thread that tries to lock the mutex.

Still to solve: undo/redo crashes.

1 files changed, 3 insertions, 0 deletions

diff --git a/source/blender/windowmanager/WM_api.h b/source/blender/windowmanager/WM_api.h
index 230784d7273..7cb24daaaef 100644
--- a/source/blender/windowmanager/WM_api.h
+++ b/source/blender/windowmanager/WM_api.h
@@ -404,6 +404,9 @@ void		WM_jobs_kill_type(struct wmWindowManager *wm, int job_type);
 
 int			WM_jobs_has_running(struct wmWindowManager *wm);
 
+void		WM_job_main_thread_lock_acquire(struct wmJob *job);
+void		WM_job_main_thread_lock_release(struct wmJob *job);
+
 			/* clipboard */
 char       *WM_clipboard_text_get(int selection);
 void        WM_clipboard_text_set(char *buf, int selection);