#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>
+int preempt_forbid_cnt;
Timer preempt_timer;
-/**
- * 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;
-}
-/**
- * Re-enable preemptive task switching.
- *
- * \sa proc_forbid()
- */
-void proc_permit(void)
-{
- /* No need to protect against interrupts here. */
- --CurrentProcess->forbid_cnt;
-}
+// fwd decl from idle.c
+void idle_init(void);
void proc_preempt(void)
void proc_preempt_timer(UNUSED_ARG(void *, param))
{
+ /* Abort if task preemption is disabled */
+ if (preempt_forbid_cnt)
+ return;
+
IRQ_DISABLE;
/*
if (!CurrentProcess->forbid_cnt)
{
TRACEMSG("preempting %p:%s", CurrentProcess, CurrentProcess->monitor.name);
- LIST_ASSERT_VALID(&ProcReadyList);
SCHED_ENQUEUE(CurrentProcess);
proc_preempt();
}
void proc_schedule(void)
{
- TRACE;
+ 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);
// Will invoke proc_preempt() in interrupt context
kill(0, SIGUSR1);
void proc_yield(void)
{
- TRACE;
+ TRACEMSG("%p:%s", CurrentProcess, proc_currentName());
- ASSERT_IRQ_ENABLED();
IRQ_DISABLE;
SCHED_ENQUEUE(CurrentProcess);
- LIST_ASSERT_VALID(&ProcReadyList);
- proc_schedule();
IRQ_ENABLE;
+
+ proc_schedule();
}
void proc_entry(void (*user_entry)(void))
proc_exit();
}
-
-static cpustack_t idle_stack[CONFIG_PROC_DEFSTACKSIZE / sizeof(cpustack_t)];
-
-/*
- * The idle process
- *
- * This process never dies and never sleeps. It's also quite apathic
- * and a bit antisocial.
- *
- * Having an idle process costs some stack space, but simplifies the
- * interrupt-driven preemption logic because there is always a user
- * context to which we can return.
- */
-static NORETURN void idle(void)
-{
- for (;;)
- {
- TRACE;
- monitor_report();
- proc_yield(); // FIXME: CPU_IDLE
- }
-}
-
void preempt_init(void)
{
MOD_CHECK(irq);
timer_setDelay(&preempt_timer, CONFIG_KERN_QUANTUM);
timer_add(&preempt_timer);
- proc_new(idle, NULL, sizeof(idle_stack), idle_stack);
+ idle_init();
}