schedule: add scheduler, thread_yield(), etc.

Could use some cleanup still...

diff --git a/Makefile b/Makefile
index becb998b162e3429c9cdaf16591325292cae7f4f..49994aca16dd05804c52b676bd8d4182d8ab3fd9 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 BIN=libthreads
-SOURCE=libthreads.c
-HEADERS=libthreads.h
+SOURCE=libthreads.c schedule.c
+HEADERS=libthreads.h schedule.h
 FLAGS=
 
 all: ${BIN}

diff --git a/libthreads.c b/libthreads.c
index 2326f3b1839e965c64b35050e4fb8384d102cc5c..c69e45ac609497e8d049a338a2edf4f85ec5e191 100644 (file)
--- a/libthreads.c
+++ b/libthreads.c
@@ -7,7 +7,7 @@
 
 #define STACK_SIZE (1024 * 1024)
 
-static struct thread *current;
+static struct thread *current, *main_thread;
 
 static void *stack_allocate(size_t size)
 {
@@ -32,7 +32,7 @@ static int create_context(struct thread *t)
        t->context.uc_stack.ss_sp = t->stack;
        t->context.uc_stack.ss_size = STACK_SIZE;
        t->context.uc_stack.ss_flags = 0;
-       t->context.uc_link = &current->context;
+       t->context.uc_link = &main_thread->context;
        makecontext(&t->context, t->start_routine, 1, t->arg);
 
        return 0;
@@ -44,6 +44,45 @@ static int create_initial_thread(struct thread *t)
        return create_context(t);
 }
 
+static int thread_swap(struct thread *old, struct thread *new)
+{
+       return swapcontext(&old->context, &new->context);
+}
+
+static int thread_yield()
+{
+       struct thread *old, *next;
+
+       DBG();
+       if (current) {
+               old = current;
+               schedule_add_thread(old);
+       } else {
+               old = main_thread;
+       }
+       schedule_choose_next(&next);
+       current = next;
+       return thread_swap(old, next);
+}
+
+static int master_thread_yield()
+{
+       struct thread *next;
+
+       DBG();
+
+       if (current) {
+               DEBUG("completed thread %d\n", current->index);
+               current->completed = 1;
+       }
+       schedule_choose_next(&next);
+       if (next && !next->completed) {
+               current = next;
+               return thread_swap(main_thread, next);
+       }
+       return 1;
+}
+
 int thread_create(struct thread *t, void (*start_routine), void *arg)
 {
        static int created = 1;
@@ -63,21 +102,26 @@ int thread_create(struct thread *t, void (*start_routine), void *arg)
 
 void thread_start(struct thread *t)
 {
-       struct thread *old = current;
        DBG();
 
-       current = t;
-       swapcontext(&old->context, &current->context);
+       schedule_add_thread(t);
+}
 
-       DBG();
+void thread_join(struct thread *t)
+{
+       while (!t->completed)
+               thread_yield();
 }
 
 void a(int *idx)
 {
        int i;
 
-       for (i = 0; i < 10; i++)
+       for (i = 0; i < 10; i++) {
                printf("Thread %d, loop %d\n", *idx, i);
+               if (i % 2)
+                       thread_yield();
+       }
 }
 
 void user_main()
@@ -91,20 +135,24 @@ void user_main()
        printf("%s() is going to start 1 thread\n", __func__);
        thread_start(&t1);
        thread_start(&t2);
+
+       thread_join(&t1);
+       thread_join(&t2);
        printf("%s() is finished\n", __func__);
 }
 
 int main()
 {
-       struct thread main_thread, user_thread;
+       struct thread user_thread;
 
-       create_initial_thread(&main_thread);
-       current = &main_thread;
+       main_thread = malloc(sizeof(struct thread));
+       create_initial_thread(main_thread);
 
        thread_create(&user_thread, &user_main, NULL);
        thread_start(&user_thread);
 
-       DBG();
+       /* Wait for all threads to complete */
+       while (master_thread_yield() == 0);
 
        DEBUG("Exiting\n");
        return 0;

diff --git a/libthreads.h b/libthreads.h
index 1323cef896f3603b4518d09f8a754e61af94e7c4..ff6d5aa975770cd1d5780e3c24ecc1a2db1ab51d 100644 (file)
--- a/libthreads.h
+++ b/libthreads.h
@@ -18,6 +18,7 @@ struct thread {
        ucontext_t context;
        void *stack;
        int index;
+       int completed;
 };
 
 int thread_create(struct thread *t, void (*start_routine), void *arg);

diff --git a/schedule.c b/schedule.c
new file mode 100644 (file)
index 0000000..e940f5a
--- /dev/null
+++ b/schedule.c
@@ -0,0 +1,56 @@
+//#define CONFIG_DEBUG
+
+#include "schedule.h"
+
+struct thread_list_node {
+       struct thread *this;
+       struct thread_list_node *next;
+       int live;
+};
+
+#define NUM_LIST_NODES 32
+
+struct thread_list_node *head, *tail;
+struct thread_list_node nodes[NUM_LIST_NODES];
+
+static void enqueue_thread(struct thread *t)
+{
+       int i;
+       struct thread_list_node *node;
+
+       for (node = nodes, i = 0; node->live && i < NUM_LIST_NODES; i++, node++);
+       if (i >= NUM_LIST_NODES)
+               printf("ran out of nodes\n");
+       node->this = t;
+       node->next = NULL;
+       node->live = 1;
+
+       if (tail)
+               tail->next = node;
+       else
+               head = node;
+       tail = node;
+}
+
+static int dequeue_thread(struct thread **t)
+{
+       if (!head)
+               return -1;
+       *t = head->this;
+       head->live = 0;
+       if (head == tail)
+               tail = NULL;
+       head = head->next;
+       return 0;
+}
+
+void schedule_add_thread(struct thread *t)
+{
+       DEBUG("%s: thread %d\n", __func__, t->index);
+       enqueue_thread(t);
+}
+
+int schedule_choose_next(struct thread **t)
+{
+       return dequeue_thread(t);
+}

diff --git a/schedule.h b/schedule.h
new file mode 100644 (file)
index 0000000..801af0d
--- /dev/null
+++ b/schedule.h
@@ -0,0 +1,9 @@
+#ifndef __SCHEDULE_H__
+#define __SCHEDULE_H__
+
+#include "libthreads.h"
+
+void schedule_add_thread(struct thread *t);
+int schedule_choose_next(struct thread **t);
+
+#endif /* __SCHEDULE_H__ */