rename cpuXXX_t to cpu_XXX_t

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

diff --git a/bertos/kern/preempt.c b/bertos/kern/preempt.c
index f285d43f5a53c3e3932f3d1d5edca9be072a26d2..4b1ad9ee2d5dea8e213570eeb1c59fc400290fa6 100644 (file)
--- a/bertos/kern/preempt.c
+++ b/bertos/kern/preempt.c
@@ -31,12 +31,26 @@
  *
  * \brief Simple preemptive multitasking scheduler.
  *
+ * All voluntary and preemptive context switching happens on exit from
+ * a common interrupt (signal) dispatcher.  Preemption on quantum timeout
+ * is regulated by a soft-timer.  Other kinds of preemption could happen
+ * if an interrupt sends a signal to a higher priority process (but this
+ * is still unimplemented).
+ *
+ * In the POSIX implementaiton, context switching is done by the portable
+ * SVR4 swapcontext() facility.
+ *
  * \version $Id: proc.c 1616 2008-08-10 19:41:26Z bernie $
  * \author Bernie Innocenti <bernie@codewiz.org>
  */
 
+#include <cfg/cfg_kern.h>
+
+#if CONFIG_KERN_PREEMPT
+
 #include "proc_p.h"
 #include "proc.h"
+#include "idle.h"
 
 #include <kern/irq.h>
 #include <kern/monitor.h>
@@ -44,22 +58,24 @@
 #include <cpu/irq.h>   // IRQ_DISABLE()...
 #include <drv/timer.h>
 #include <cfg/module.h>
+#include <cfg/depend.h>    // CONFIG_DEPEND()
 
+// Check config dependencies
+CONFIG_DEPEND(CONFIG_KERN_PREEMPT,    CONFIG_KERN_SCHED && CONFIG_TIMER_EVENTS && CONFIG_KERN_IRQ);
 
-int preempt_forbid_cnt;
-
-static Timer preempt_timer;
+MOD_DEFINE(preempt)
 
+/// Global preemption disabling nesting counter
+cpu_atomic_t _preempt_forbid_cnt;
 
-// fwd decl from idle.c
-void idle_init(void);
+static Timer preempt_timer;
 
 
-void proc_preempt(void)
+void proc_schedule(void)
 {
        IRQ_DISABLE;
 
-       ASSERT(preempt_forbid_cnt == 0);
+       ASSERT(proc_allowed());
        LIST_ASSERT_VALID(&ProcReadyList);
        CurrentProcess = (struct Process *)list_remHead(&ProcReadyList);
        ASSERT2(CurrentProcess, "no idle proc?");
@@ -69,9 +85,9 @@ void proc_preempt(void)
        TRACEMSG("launching %p:%s", CurrentProcess, proc_currentName());
 }
 
-void proc_preempt_timer(UNUSED_ARG(void *, param))
+void proc_preempt(UNUSED_ARG(void *, param))
 {
-       if (!preempt_forbid_cnt)
+       if (proc_allowed())
        {
                IRQ_DISABLE;
 
@@ -82,9 +98,11 @@ void proc_preempt_timer(UNUSED_ARG(void *, param))
                #endif
 
                TRACEMSG("preempting %p:%s", CurrentProcess, proc_currentName());
+
+// FIXME: this still breaks havoc, probably because of some reentrancy issue
 #if 0
                SCHED_ENQUEUE(CurrentProcess);
-               proc_preempt();
+               proc_schedule();
 #endif
                #if CONFIG_KERN_PRI
                        }
@@ -97,17 +115,17 @@ void proc_preempt_timer(UNUSED_ARG(void *, param))
        timer_add(&preempt_timer);
 }
 
-void proc_schedule(void)
+void proc_switch(void)
 {
        ATOMIC(LIST_ASSERT_VALID(&ProcReadyList));
        TRACEMSG("%p:%s", CurrentProcess, proc_currentName());
        ATOMIC(LIST_ASSERT_VALID(&ProcReadyList));
 
        /* Sleeping with IRQs disabled or preemption forbidden is illegal */
-       ASSERT_IRQ_ENABLED();
-       ASSERT(preempt_forbid_cnt == 0);
+       IRQ_ASSERT_ENABLED();
+       ASSERT(proc_allowed());
 
-       // Will invoke proc_preempt() in interrupt context
+       // Will invoke proc_switch() in interrupt context
        kill(0, SIGUSR1);
 }
 
@@ -119,7 +137,7 @@ void proc_yield(void)
        SCHED_ENQUEUE(CurrentProcess);
        IRQ_ENABLE;
 
-       proc_schedule();
+       proc_switch();
 }
 
 void proc_entry(void (*user_entry)(void))
@@ -133,11 +151,15 @@ void preempt_init(void)
        MOD_CHECK(irq);
        MOD_CHECK(timer);
 
-       irq_register(SIGUSR1, proc_preempt);
+       irq_register(SIGUSR1, proc_schedule);
 
-       timer_setSoftint(&preempt_timer, proc_preempt_timer, NULL);
+       timer_setSoftint(&preempt_timer, proc_preempt, NULL);
        timer_setDelay(&preempt_timer, CONFIG_KERN_QUANTUM);
        timer_add(&preempt_timer);
 
        idle_init();
+
+       MOD_INIT(preempt);
 }
+
+#endif // CONFIG_KERN_PREEMPT