From a21c3f45bc9b6705763d2d79e627aebff4b312e5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ren=C3=A9=20Kijewski?= <rene.kijewski@fu-berlin.de>
Date: Tue, 10 Jun 2014 16:55:04 +0200
Subject: [PATCH] core: remove unnecessary tests in sched.c

The scheduling gets activated by `kernel_init()` calling
`cpu_switch_context_exit()`. Before this `sched_run()` won't be called.
When it gets called, at least the main thread and the idle thread are
spawned. The idle thread won't die / get killed. So there always is at
least one thread in `runqueue_bitcache`.

Closes #19.
---
 core/sched.c | 59 ++++++++++++++++++++--------------------------------
 1 file changed, 22 insertions(+), 37 deletions(-)

diff --git a/core/sched.c b/core/sched.c
index 7004d35876..bb717d0e38 100644
--- a/core/sched.c
+++ b/core/sched.c
@@ -69,11 +69,9 @@ void sched_run(void)
         }
 
 #ifdef SCHED_TEST_STACK
-
         if (*((unsigned int *)my_active_thread->stack_start) != (unsigned int) my_active_thread->stack_start) {
             printf("scheduler(): stack overflow detected, task=%s pid=%u\n", my_active_thread->name, my_active_thread->pid);
         }
-
 #endif
 
     }
@@ -84,47 +82,34 @@ void sched_run(void)
     if (my_active_thread && (sched_pidlist[my_active_thread->pid].laststart)) {
         sched_pidlist[my_active_thread->pid].runtime_ticks += time - sched_pidlist[my_active_thread->pid].laststart;
     }
-
 #endif
 
     DEBUG("\nscheduler: previous task: %s\n", (my_active_thread == NULL) ? "none" : my_active_thread->name);
 
-    if (sched_num_threads == 0) {
-        DEBUG("scheduler: no tasks left.\n");
+    /* The bitmask in runqueue_bitcache is never empty,
+     * since the threading should not be started before at least the idle thread was started.
+     */
+    int nextrq = bitarithm_lsb(runqueue_bitcache);
+    clist_node_t next = *(sched_runqueues[nextrq]);
+    DEBUG("scheduler: first in queue: %s\n", ((tcb_t *)next.data)->name);
+    clist_advance(&(sched_runqueues[nextrq]));
+    my_active_thread = (tcb_t *)next.data;
+    sched_active_pid = (volatile int) my_active_thread->pid;
 
-        while (!sched_num_threads) {
-            /* loop until a new task arrives */
-            ;
-        }
-
-        DEBUG("scheduler: new task created.\n");
-    }
-
-    my_active_thread = NULL;
-
-    while (!my_active_thread) {
-        int nextrq = bitarithm_lsb(runqueue_bitcache);
-        clist_node_t next = *(sched_runqueues[nextrq]);
-        DEBUG("scheduler: first in queue: %s\n", ((tcb_t *)next.data)->name);
-        clist_advance(&(sched_runqueues[nextrq]));
-        my_active_thread = (tcb_t *)next.data;
-        sched_active_pid = (volatile int) my_active_thread->pid;
 #if SCHEDSTATISTICS
-        sched_pidlist[my_active_thread->pid].laststart = time;
-        sched_pidlist[my_active_thread->pid].schedules++;
-        if ((sched_cb) && (my_active_thread->pid != thread_last_pid)) {
-            sched_cb(hwtimer_now(), my_active_thread->pid);
-            thread_last_pid = my_active_thread->pid;
-        }
-#endif
-#ifdef MODULE_NSS
-
-        if (sched_active_thread && sched_active_thread->pid != thread_last_pid) {
-            thread_last_pid = sched_active_thread->pid;
-        }
-
-#endif
+    sched_pidlist[my_active_thread->pid].laststart = time;
+    sched_pidlist[my_active_thread->pid].schedules++;
+    if ((sched_cb) && (sched_active_thread != thread_last_pid)) {
+        sched_cb(hwtimer_now(), my_active_thread->pid);
+        thread_last_pid = my_active_thread->pid;
     }
+#endif
+
+#ifdef MODULE_NSS
+    if (sched_active_thread && sched_active_thread != thread_last_pid) {
+        thread_last_pid = sched_active_thread;
+    }
+#endif
 
     DEBUG("scheduler: next task: %s\n", my_active_thread->name);
 
@@ -198,7 +183,7 @@ NORETURN void sched_task_exit(void)
     sched_threads[sched_active_thread->pid] = NULL;
     sched_num_threads--;
 
-    sched_set_status((tcb_t *)sched_active_thread,  STATUS_STOPPED);
+    sched_set_status((tcb_t *)sched_active_thread, STATUS_STOPPED);
 
     sched_active_thread = NULL;
     cpu_switch_context_exit();