Choose task thread in rust_scheduler by round robin

src/rt/rust_scheduler.cpp

@@ -11,9 +11,9 @@ rust_scheduler::rust_scheduler(rust_kernel *kernel,
     live_threads(num_threads),
     live_tasks(0),
     num_threads(num_threads),
+    cur_thread(0),
     id(id)
 {
-    isaac_init(kernel, &rctx);
     create_task_threads();
 }
 
@@ -86,9 +86,11 @@ rust_task *
 rust_scheduler::create_task(rust_task *spawner, const char *name) {
     size_t thread_no;
     {
-	scoped_lock with(lock);
-	thread_no = isaac_rand(&rctx) % num_threads;
-	live_tasks++;
+        scoped_lock with(lock);
+        live_tasks++;
+        thread_no = cur_thread++;
+        if (cur_thread >= num_threads)
+            cur_thread = 0;
     }
     rust_task_thread *thread = threads[thread_no];
     return thread->create_task(spawner, name);
@@ -98,11 +100,11 @@ void
 rust_scheduler::release_task() {
     bool need_exit = false;
     {
-	scoped_lock with(lock);
-	live_tasks--;
-	if (live_tasks == 0) {
-	    need_exit = true;
-	}
+        scoped_lock with(lock);
+        live_tasks--;
+        if (live_tasks == 0) {
+            need_exit = true;
+        }
     }
     if (need_exit) {
 	// There are no more tasks on this scheduler. Time to leave
@@ -129,10 +131,10 @@ void
 rust_scheduler::release_task_thread() {
     uintptr_t new_live_threads;
     {
-	scoped_lock with(lock);
-	new_live_threads = --live_threads;
+        scoped_lock with(lock);
+        new_live_threads = --live_threads;
     }
     if (new_live_threads == 0) {
-	kernel->release_scheduler_id(id);
+        kernel->release_scheduler_id(id);
     }
 }

src/rt/rust_scheduler.h

@@ -10,16 +10,16 @@ class rust_scheduler : public kernel_owned<rust_scheduler> {
     rust_srv *srv;
     rust_env *env;
 private:
-    // Protects the random number context and live_threads
+    // Protects live_threads and cur_thread increments
     lock_and_signal lock;
     // When this hits zero we'll tell the kernel to release us
     uintptr_t live_threads;
     // When this hits zero we'll tell the threads to exit
     uintptr_t live_tasks;
-    randctx rctx;
 
     array_list<rust_task_thread *> threads;
     const size_t num_threads;
+    size_t cur_thread;
 
     rust_sched_id id;