Initial commit

src/generic/time.c

@@ -0,0 +1,96 @@
+/*
+ * Time.
+ *
+ * Copyright (C) 2007 Bahadir Balban
+ *
+ */
+#include <l4/types.h>
+#include <l4/lib/mutex.h>
+#include <l4/lib/printk.h>
+#include <l4/generic/irq.h>
+#include <l4/generic/scheduler.h>
+#include <l4/generic/time.h>
+#include INC_ARCH(exception.h)
+
+/* TODO:
+ * 1) Add RTC support.
+ * 2) Need to calculate time since EPOCH,
+ * 3) Jiffies must be initialised to a reasonable value.
+ */
+
+volatile u32 jiffies;
+
+static inline void increase_jiffies(void)
+{
+	jiffies++;
+}
+
+
+static int noticks_noresched = 0;
+
+/*
+ * Check preemption anomalies:
+ *
+ * This checks how many times no rescheduling has occured even though ticks
+ * reached zero. This suggests that preemption was enabled for more than a timer
+ * interval. Normally, even if a preemption irq occured during a non-preemptive
+ * state, preemption is *guaranteed* to occur before the next irq, provided that
+ * the non-preemptive period is less than a timer irq interval (and it must be).
+ *
+ * Time:
+ *
+ * |-|---------------------|-|-------------------->
+ * | V                     | V
+ * | Preemption irq()      | Next irq.
+ * V                       V
+ * preempt_disabled()   preempt_enabled() && preemption;
+ */
+void check_noticks_noresched(void)
+{
+	if (!current->ticks_left)
+		noticks_noresched++;
+
+	if (noticks_noresched >= 2) {
+		printk("Warning, no ticks and yet no rescheduling "
+		       "for %d times.\n", noticks_noresched);
+		printk("Spending more than a timer period"
+		       " as nonpreemptive!!!\n");
+	}
+}
+
+void update_process_times(void)
+{
+	struct ktcb *cur = current;
+
+	BUG_ON(cur->ticks_left < 0);
+
+	/*
+	 * If preemption is disabled we stop reducing ticks when it reaches 0
+	 * but set need_resched so that as soon as preempt-enabled, scheduling
+	 * occurs.
+	 */
+	if (cur->ticks_left == 0) {
+		need_resched = 1;
+		// check_noticks_noresched();
+		return;
+	}
+	// noticks_noresched = 0;
+
+	if (in_kernel())
+		cur->kernel_time++;
+	else
+		cur->user_time++;
+
+	cur->ticks_left--;
+	if (!cur->ticks_left)
+		need_resched = 1;
+}
+
+
+int do_timer_irq(void)
+{
+	increase_jiffies();
+	update_process_times();
+	return IRQ_HANDLED;
+}
+