*
* \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>
#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;
-
-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(proc_allowed());
LIST_ASSERT_VALID(&ProcReadyList);
CurrentProcess = (struct Process *)list_remHead(&ProcReadyList);
- LIST_ASSERT_VALID(&ProcReadyList);
ASSERT2(CurrentProcess, "no idle proc?");
IRQ_ENABLE;
- TRACEMSG("new proc: %p:%s", CurrentProcess, CurrentProcess ? CurrentProcess->monitor.name : "---");
- monitor_report();
+ TRACEMSG("launching %p:%s", CurrentProcess, proc_currentName());
}
-void proc_preempt_timer(UNUSED_ARG(void *, param))
+void proc_preempt(UNUSED_ARG(void *, param))
{
- /* Abort if task preemption is disabled */
- if (preempt_forbid_cnt)
- return;
-
- IRQ_DISABLE;
-/*
- if (!CurrentProcess->forbid_cnt)
+ if (proc_allowed())
{
- TRACEMSG("preempting %p:%s", CurrentProcess, CurrentProcess->monitor.name);
+ IRQ_DISABLE;
+
+ #if CONFIG_KERN_PRI
+ Process *rival = (Process *)LIST_HEAD(&ProcReadyList);
+ if (rival && rival->link.pri >= CurrentProcess->link.pri)
+ {
+ #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
+ }
+ #endif
+
+ IRQ_ENABLE;
}
-*/
- IRQ_ENABLE;
timer_setDelay(&preempt_timer, CONFIG_KERN_QUANTUM);
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);
}
SCHED_ENQUEUE(CurrentProcess);
IRQ_ENABLE;
- proc_schedule();
+ proc_switch();
}
void proc_entry(void (*user_entry)(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