* invalidate any other reasons why the executable file might be covered by
* the GNU General Public License.
*
- * Copyright 2001, 2004 Develer S.r.l. (http://www.develer.com/)
- * Copyright 1999, 2000, 2001, 2008 Bernie Innocenti <bernie@codewiz.org>
+ * Copyright 2008 Bernie Innocenti <bernie@codewiz.org>
* -->
*
- * \brief Simple realtime multitasking scheduler.
- * Context switching is only done cooperatively.
+ * \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>
- * \author Stefano Fedrigo <aleph@develer.com>
*/
+#include "cfg/cfg_proc.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/frame.h> // CPU_IDLE
+#include <cpu/irq.h> // IRQ_DISABLE()...
+#include <drv/timer.h>
+#include <cfg/module.h>
+#include <cfg/depend.h> // CONFIG_DEPEND()
-#include <unistd.h> // XXX alarm()
+// Check config dependencies
+CONFIG_DEPEND(CONFIG_KERN_PREEMPT, CONFIG_KERN && CONFIG_TIMER_EVENTS && CONFIG_KERN_IRQ);
+MOD_DEFINE(preempt)
-/*
- * The time sharing scheduler forces a task switch when the current
- * process has exhausted its quantum.
- */
-uint16_t Quantum;
+/// Global preemption disabling nesting counter
+cpu_atomic_t _preempt_forbid_cnt;
-/**
- * Disable preemptive task switching.
- *
- * The scheduler maintains a per-process nesting counter. Task switching is
- * effectively re-enabled only when the number of calls to proc_permit()
- * matches the number of calls to proc_forbid().
- *
- * Calling functions that could sleep while task switching is disabled
- * is dangerous, although supported. Preemptive task switching is
- * resumed while the process is sleeping and disabled again as soon as
- * it wakes up again.
- *
- * \sa proc_permit()
- */
-void proc_forbid(void)
-{
- /* No need to protect against interrupts here. */
- ++CurrentProcess->forbid_cnt;
-}
+static Timer preempt_timer;
-/**
- * Re-enable preemptive task switching.
- *
- * \sa proc_forbid()
- */
-void proc_permit(void)
+
+void proc_schedule(void)
{
- /* No need to protect against interrupts here. */
- --CurrentProcess->forbid_cnt;
-}
+ IRQ_DISABLE;
-static void (*irq_handlers[100])(void); // FIXME
+ ASSERT(proc_allowed());
+ LIST_ASSERT_VALID(&ProcReadyList);
+ CurrentProcess = (struct Process *)list_remHead(&ProcReadyList);
+ ASSERT2(CurrentProcess, "no idle proc?");
+ IRQ_ENABLE;
-void proc_preempt(void)
+ TRACEMSG("launching %p:%s", CurrentProcess, proc_currentName());
+}
+
+void proc_preempt(UNUSED_ARG(void *, param))
{
- TRACE;
+ if (proc_allowed())
+ {
+ IRQ_DISABLE;
- ATOMIC(LIST_ASSERT_VALID(&ProcReadyList));
+ #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_schedule();
+#endif
+ #if CONFIG_KERN_PRI
+ }
+ #endif
- IRQ_DISABLE;
- /* Poll on the ready queue for the first ready process */
- 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.
- */
IRQ_ENABLE;
- CPU_IDLE;
- MEMORY_BARRIER;
- IRQ_DISABLE;
}
- IRQ_ENABLE;
+
+ timer_setDelay(&preempt_timer, CONFIG_KERN_QUANTUM);
+ timer_add(&preempt_timer);
}
-void proc_preempt_timer(void)
+void proc_switch(void)
{
- // TODO: check Quantum
+ ATOMIC(LIST_ASSERT_VALID(&ProcReadyList));
+ TRACEMSG("%p:%s", CurrentProcess, proc_currentName());
+ ATOMIC(LIST_ASSERT_VALID(&ProcReadyList));
- alarm(1);
- ATOMIC(SCHED_ENQUEUE(CurrentProcess));
- proc_schedule();
-}
+ /* Sleeping with IRQs disabled or preemption forbidden is illegal */
+ IRQ_ASSERT_ENABLED();
+ ASSERT(proc_allowed());
-void proc_schedule(void)
-{
+ // Will invoke proc_switch() in interrupt context
kill(0, SIGUSR1);
}
void proc_yield(void)
{
- ATOMIC(SCHED_ENQUEUE(CurrentProcess));
+ TRACEMSG("%p:%s", CurrentProcess, proc_currentName());
- proc_schedule();
+ IRQ_DISABLE;
+ SCHED_ENQUEUE(CurrentProcess);
+ IRQ_ENABLE;
+
+ proc_switch();
}
-/* signal handler */
-void irq_entry(int signum)
+void proc_entry(void (*user_entry)(void))
{
- Process *old_process;
-
- TRACEMSG("storing %p:%s", CurrentProcess, CurrentProcess->monitor.name);
- CurrentProcess->leaving = false;
- getcontext(&CurrentProcess->context);
- /* We get here in two ways: directly, and after setcontext() below */
+ user_entry();
+ proc_exit();
+}
- if (CurrentProcess->leaving)
- {
- TRACEMSG("leaving to %p:%s", CurrentProcess, CurrentProcess->monitor.name);
- return;
- }
+void preempt_init(void)
+{
+ MOD_CHECK(irq);
+ MOD_CHECK(timer);
- old_process = CurrentProcess;
+ irq_register(SIGUSR1, proc_schedule);
- irq_handlers[signum]();
+ timer_setSoftint(&preempt_timer, proc_preempt, NULL);
+ timer_setDelay(&preempt_timer, CONFIG_KERN_QUANTUM);
+ timer_add(&preempt_timer);
- if (old_process != CurrentProcess)
- {
- TRACEMSG("launching %p:%s", CurrentProcess, CurrentProcess->monitor.name);
- CurrentProcess->leaving = true;
- setcontext(&CurrentProcess->context);
- /* not reached */
- }
+ idle_init();
- TRACEMSG("keeping %p:%s", CurrentProcess, CurrentProcess->monitor.name);
+ MOD_INIT(preempt);
}
-void preempt_init(void)
-{
- struct sigaction act;
- act.sa_handler = irq_entry;
- sigemptyset(&act.sa_mask);
- sigaddset(&act.sa_mask, SIGUSR1);
- sigaddset(&act.sa_mask, SIGALRM);
- act.sa_flags = SA_RESTART; /* | SA_SIGINFO; */
-
- irq_handlers[SIGUSR1] = proc_preempt;
- irq_handlers[SIGALRM] = proc_preempt_timer;
- sigaction(SIGUSR1, &act, NULL);
- sigaction(SIGALRM, &act, NULL);
-
- alarm(1); // FIXME
-}
+#endif // CONFIG_KERN_PREEMPT
projects / bertos.git / blobdiff