From 81a58004d51547d074b4218f906b0b95f2b2c5dc Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Thu, 4 Aug 2022 15:58:54 +0200
Subject: syscalls: add _syscall_sleep()

---
 src/kernel/arch/amd64/time.c | 50 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)
 create mode 100644 src/kernel/arch/amd64/time.c

(limited to 'src/kernel/arch/amd64/time.c')

diff --git a/src/kernel/arch/amd64/time.c b/src/kernel/arch/amd64/time.c
new file mode 100644
index 0000000..d6e53dd
--- /dev/null
+++ b/src/kernel/arch/amd64/time.c
@@ -0,0 +1,50 @@
+#include <kernel/arch/amd64/time.h>
+#include <kernel/panic.h>
+#include <kernel/proc.h>
+
+static uint64_t uptime = 0, goal = ~0;
+static struct process *scheduled = NULL;
+
+uint64_t uptime_ms(void) { return uptime; }
+
+static void update_goal(void) {
+	goal = scheduled ? scheduled->waits4timer.goal : ~(uint64_t)0;
+}
+
+void pit_irq(void) {
+	// TODO inefficient - getting here executes a lot of code which could just be a few lines of asm
+	uptime++;
+	if (uptime < goal) return;
+
+	struct process *p = scheduled;
+	assert(p);
+	scheduled = p->waits4timer.next;
+	process_transition(p, PS_RUNNING);
+	update_goal();
+}
+
+void timer_schedule(struct process *p, uint64_t time) {
+	process_transition(p, PS_WAITS4TIMER);
+	p->waits4timer.goal = time;
+
+	struct process **slot = &scheduled;
+	while (*slot && (*slot)->waits4timer.goal <= time) {
+		assert((*slot)->state == PS_WAITS4TIMER);
+		slot = &(*slot)->waits4timer.next;
+	}
+	p->waits4timer.next = *slot;
+	*slot = p;
+	update_goal();
+}
+
+void timer_deschedule(struct process *p) {
+	assert(p->state == PS_WAITS4TIMER);
+
+	struct process **slot = &scheduled;
+	while (*slot && *slot != p)
+		slot = &(*slot)->waits4timer.next;
+	assert(*slot);
+	*slot = p->waits4timer.next;
+
+	update_goal();
+}
-- 
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