Merge from trunk.

[bertos.git] / bertos / kern / coop.c

diff --git a/bertos/kern/coop.c b/bertos/kern/coop.c
index 4b2e6b88a5c303598391e776789e4007f67e7681..542ed67844a7dc0acddb63196369c68572a50c31 100644 (file)
--- a/bertos/kern/coop.c
+++ b/bertos/kern/coop.c
@@ -32,7 +32,7 @@
  *
  * \brief Simple cooperative multitasking scheduler.
  *
- * \version $Id: proc.c 1616 2008-08-10 19:41:26Z bernie $
+ * \version $Id$
  * \author Bernie Innocenti <bernie@codewiz.org>
  * \author Stefano Fedrigo <aleph@develer.com>
  */
@@ -51,90 +51,53 @@
 #include <cpu/frame.h>
 
 /**
- * CPU dependent context switching routines.
+ * Define function prototypes exported outside.
  *
- * Saving and restoring the context on the stack is done by a CPU-dependent
- * support routine which usually needs to be written in assembly.
+ * Required to silent gcc "no previous prototype" warnings.
  */
-EXTERN_C void asm_switch_context(cpustack_t **new_sp, cpustack_t **save_sp);
-
+void coop_yield(void);
+void coop_switch(void);
+void coop_wakeup(Process *proc);
 
 /**
- * System scheduler: pass CPU control to the next process in
- * the ready queue.
+ * Give the control of the CPU to another process.
+ *
+ * \note Assume the current process has been already added to a wait queue.
+ *
+ * \warning This should be considered an internal kernel function, even if it
+ * is allowed, usage from application code is strongly discouraged.
  */
-void proc_schedule(void)
+void coop_switch(void)
 {
-       struct Process *old_process;
-       cpuflags_t flags;
-
-       ATOMIC(LIST_ASSERT_VALID(&ProcReadyList));
-       ASSERT_USER_CONTEXT();
-       ASSERT_IRQ_ENABLED();
-
-       /* Remember old process to save its context later */
-       old_process = CurrentProcess;
+       ATOMIC(proc_schedule());
+}
 
-       /* Poll on the ready queue for the first ready process */
-       IRQ_SAVE_DISABLE(flags);
-       while (!(CurrentProcess = (struct Process *)list_remHead(&ProcReadyList)))
-       {
-               /*
-                * Make sure we physically reenable interrupts here, no matter what
-                * the current task status is. This is important because if we
-                * are idle-spinning, we must allow interrupts, otherwise no
-                * process will ever wake up.
-                *
-                * During idle-spinning, an interrupt can occur and it may
-                * modify \p ProcReadyList. To ensure that compiler reload this
-                * variable every while cycle we call CPU_MEMORY_BARRIER.
-                * The memory barrier ensure that all variables used in this context
-                * are reloaded.
-                * \todo If there was a way to write sig_wait() so that it does not
-                * disable interrupts while waiting, there would not be any
-                * reason to do this.
-                */
-               IRQ_ENABLE;
-               CPU_IDLE;
-               MEMORY_BARRIER;
-               IRQ_DISABLE;
-       }
-       IRQ_RESTORE(flags);
+/**
+ * Immediately wakeup a process, dispatching it to the CPU.
+ */
+void coop_wakeup(Process *proc)
+{
+       ASSERT(proc_preemptAllowed());
+       ASSERT(current_process);
+       IRQ_ASSERT_DISABLED();
 
-       /*
-        * Optimization: don't switch contexts when the active
-        * process has not changed.
-        */
-       if (CurrentProcess != old_process)
+       if (prio_proc(proc) >= prio_curr())
        {
-               cpustack_t *dummy;
-
-               #if CONFIG_KERN_MONITOR
-                       LOG_INFO("Switch from %p(%s) to %p(%s)\n",
-                               old_process,    old_process ? old_process->monitor.name : "NONE",
-                               CurrentProcess, CurrentProcess->monitor.name);
-               #endif
+               Process *old_process = current_process;
 
-               /* Save context of old process and switch to new process. If there is no
-                * old process, we save the old stack pointer into a dummy variable that
-                * we ignore. In fact, this happens only when the old process has just
-                * exited.
-                * TODO: Instead of physically clearing the process at exit time, a zombie
-                * list should be created.
-                */
-               asm_switch_context(&CurrentProcess->stack, old_process ? &old_process->stack : &dummy);
+               SCHED_ENQUEUE(current_process);
+               current_process = proc;
+               proc_switchTo(current_process, old_process);
        }
-
-       /* This RET resumes the execution on the new process */
+       else
+               SCHED_ENQUEUE_HEAD(proc);
 }
 
-
 /**
  * Co-operative context switch
  */
-void proc_yield(void)
+void coop_yield(void)
 {
-       ATOMIC(SCHED_ENQUEUE(CurrentProcess));
-
-       proc_schedule();
+       ATOMIC(SCHED_ENQUEUE(current_process));
+       coop_switch();
 }