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, 46 insertions, 0 deletions

diff --git a/source/blender/blenlib/intern/threads.c b/source/blender/blenlib/intern/threads.c
index e0ea3bbf685..2b6fb52c49c 100644
--- a/source/blender/blenlib/intern/threads.c
+++ b/source/blender/blenlib/intern/threads.c
@@ -508,6 +508,52 @@ void BLI_rw_mutex_free(ThreadRWMutex *mutex)
 	MEM_freeN(mutex);
 }
 
+/* Ticket Mutex Lock */
+
+struct TicketMutex {
+	pthread_cond_t cond;
+	pthread_mutex_t mutex;
+	unsigned int queue_head, queue_tail;
+};
+
+TicketMutex *BLI_ticket_mutex_alloc(void)
+{
+	TicketMutex *ticket = MEM_callocN(sizeof(TicketMutex), "TicketMutex");
+
+	pthread_cond_init(&ticket->cond, NULL);
+	pthread_mutex_init(&ticket->mutex, NULL);
+
+	return ticket;
+}
+
+void BLI_ticket_mutex_free(TicketMutex *ticket)
+{
+	pthread_mutex_destroy(&ticket->mutex);
+	pthread_cond_destroy(&ticket->cond);
+	MEM_freeN(ticket);
+}
+
+void BLI_ticket_mutex_lock(TicketMutex *ticket)
+{
+	unsigned int queue_me;
+
+	pthread_mutex_lock(&ticket->mutex);
+	queue_me = ticket->queue_tail++;
+
+	while (queue_me != ticket->queue_head)
+		pthread_cond_wait(&ticket->cond, &ticket->mutex);
+
+	pthread_mutex_unlock(&ticket->mutex);
+}
+
+void BLI_ticket_mutex_unlock(TicketMutex *ticket)
+{
+	pthread_mutex_lock(&ticket->mutex);
+	ticket->queue_head++;
+	pthread_cond_broadcast(&ticket->cond);
+	pthread_mutex_unlock(&ticket->mutex);
+}
+
 /* ************************************************ */
 
 typedef struct ThreadedWorker {