More documentation for sched.c (#1219)

* More documentation for sched.c

* VI retrace -> vertical retrace, attempt to clarify comment in viconfig

* Further review changes, fix inconsistent capitalization of PreNMI (PRENMI -> PreNMI)

* Fix typo

Co-authored-by: engineer124 <47598039+engineer124@users.noreply.github.com>

* Change TaskSwapBuffer, change comment on OS_SC_DRAM_DLIST to unimplemented

* Rename SchedContext/gSchedContext to Scheduler/gScheduler

* Comments fixes

Co-authored-by: Dragorn421 <Dragorn421@users.noreply.github.com>

* Format

Co-authored-by: engineer124 <47598039+engineer124@users.noreply.github.com>
Co-authored-by: Dragorn421 <Dragorn421@users.noreply.github.com>

1 files changed, 27 insertions, 0 deletions

diff --git a/src/code/z_nulltask.c b/src/code/z_nulltask.c
new file mode 100644
index 000000000..1f7dae689
--- /dev/null
+++ b/src/code/z_nulltask.c
@@ -0,0 +1,27 @@
+#include "global.h"
+
+/**
+ * Blocks the current thread until all queued scheduler tasks have completed.
+ */
+void Sched_FlushTaskQueue(void) {
+    OSScTask task;
+    OSMesgQueue queue;
+    OSMesg msg;
+
+    // Prepare a "NULL" task
+    task.next = NULL;
+    task.flags = OS_SC_NEEDS_RDP | OS_SC_NEEDS_RSP;
+    task.msgQueue = &queue;
+    task.msg = NULL;
+    task.framebuffer = NULL;
+    task.list.t.type = M_NULTASK;
+    osCreateMesgQueue(task.msgQueue, &msg, 1);
+
+    // Send it to and wake up the scheduler
+    osSendMesg(&gScheduler.cmdQueue, (OSMesg)&task, OS_MESG_BLOCK);
+    Sched_Notify(&gScheduler);
+
+    // Wait until the task has been processed, indicating that no task is
+    // running and the task queue is now empty.
+    osRecvMesg(&queue, NULL, OS_MESG_BLOCK);
+}