From 8b2af1dd4772675680b8b23808886de5ce688cbc Mon Sep 17 00:00:00 2001
From: Brian Norris <banorris@uci.edu>
Date: Wed, 7 Mar 2012 18:10:59 -0800
Subject: [PATCH] initial commit

Basic working copy of "threads," which execute until completion as soon as
they are launched.
---
 Makefile     |  11 +++++
 libthreads.c | 121 +++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 132 insertions(+)
 create mode 100644 Makefile
 create mode 100644 libthreads.c

diff --git a/Makefile b/Makefile
new file mode 100644
index 00000000..25b9459a
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,11 @@
+BIN=libthreads
+SOURCE=libthreads.c
+FLAGS=
+
+all: ${BIN}
+
+${BIN}: ${SOURCE}
+	gcc -o ${BIN} ${SOURCE} ${FLAGS}
+
+clean:
+	rm -f ${BIN} *.o
diff --git a/libthreads.c b/libthreads.c
new file mode 100644
index 00000000..5f442b20
--- /dev/null
+++ b/libthreads.c
@@ -0,0 +1,121 @@
+#include <string.h>
+#include <stdlib.h>
+#include <ucontext.h>
+#include <stdio.h>
+
+//#define CONFIG_DEBUG
+
+#ifdef CONFIG_DEBUG
+#define DBG() do { printf("Here: %s, L%d\n", __func__, __LINE__); } while (0)
+#define DEBUG(fmt, ...) printf(fmt, ##__VA_ARGS__)
+#else
+#define DBG()
+#define DEBUG(fmt, ...)
+#endif
+
+#define STACK_SIZE (1024 * 1024)
+
+struct thread {
+	void (*start_routine);
+	void *arg;
+	ucontext_t context;
+	void *stack;
+	int started;
+	int index;
+};
+
+static struct thread *current;
+static ucontext_t *cleanup;
+
+static void *stack_allocate(size_t size)
+{
+	return malloc(size);
+}
+
+int thread_create(struct thread *t, void (*start_routine), void *arg)
+{
+	static int created;
+	ucontext_t local;
+
+	DBG();
+
+	t->index = created++;
+	DEBUG("create thread %d\n", t->index);
+
+	t->start_routine = start_routine;
+	t->arg = arg;
+	t->started = 0;
+
+	/* Initialize state */
+	getcontext(&t->context);
+	t->stack = stack_allocate(STACK_SIZE);
+	t->context.uc_stack.ss_sp = t->stack;
+	t->context.uc_stack.ss_size = STACK_SIZE;
+	t->context.uc_stack.ss_flags = 0;
+	if (current)
+		t->context.uc_link = &current->context;
+	else
+		t->context.uc_link = cleanup;
+	makecontext(&t->context, t->start_routine, 1, t->arg);
+
+	return 0;
+}
+
+void thread_start(struct thread *t)
+{
+	DBG();
+
+	t->started = 1;
+	
+	if (current) {
+		struct thread *old = current;
+		current = t;
+		swapcontext(&old->context, &current->context);
+	} else {
+		current = t;
+		swapcontext(cleanup, &current->context);
+	}
+	DBG();
+}
+
+void a(int *idx)
+{
+	int i;
+
+	for (i = 0; i < 10; i++)
+		printf("Thread %d, loop %d\n", *idx, i);
+}
+
+void user_main()
+{
+	struct thread t1, t2;
+	int i = 1, j = 2;
+
+	thread_create(&t1, &a, &i);
+	thread_create(&t2, &a, &j);
+
+	printf("user_main() is going to start 2 threads\n");
+	thread_start(&t1);
+	thread_start(&t2);
+	printf("user_main() is finished\n");
+}
+
+int main()
+{
+	struct thread t;
+	ucontext_t main_context;
+	int pass = 0;
+
+	cleanup = &main_context;
+
+	thread_create(&t, &user_main, NULL);
+
+	getcontext(&main_context);
+	if (!pass++)
+		thread_start(&t);
+
+	DBG();
+
+	DEBUG("Exiting?\n");
+	return 0;
+}
-- 
2.34.1