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, 12 insertions, 0 deletions

diff --git a/source/blender/blenlib/BLI_threads.h b/source/blender/blenlib/BLI_threads.h
index 331cac3ed76..154986936a2 100644
--- a/source/blender/blenlib/BLI_threads.h
+++ b/source/blender/blenlib/BLI_threads.h
@@ -131,6 +131,18 @@ void BLI_rw_mutex_free(ThreadRWMutex *mutex);
 void BLI_rw_mutex_lock(ThreadRWMutex *mutex, int mode);
 void BLI_rw_mutex_unlock(ThreadRWMutex *mutex);
 
+/* Ticket Mutex Lock
+ *
+ * This is a 'fair' mutex in that it will grant the lock to the first thread
+ * that requests it. */
+
+typedef struct TicketMutex TicketMutex;
+
+TicketMutex *BLI_ticket_mutex_alloc(void);
+void BLI_ticket_mutex_free(TicketMutex *ticket);
+void BLI_ticket_mutex_lock(TicketMutex *ticket);
+void BLI_ticket_mutex_unlock(TicketMutex *ticket);
+
 /* ThreadedWorker
  *
  * A simple tool for dispatching work to a limited number of threads