#include "random.h"
#include "switch.h"
+/* Offset of `stack' member within `struct thread'.
+ Used by switch.S, which can't figure it out on its own. */
uint32_t thread_stack_ofs = offsetof (struct thread, stack);
+/* List of processes in THREAD_READY state, that is, processes
+ that are ready to run but not actually running. */
static struct list run_queue;
+
+/* Thread to run when nothing else is ready. */
static struct thread *idle_thread;
+static struct thread *find_next_to_run (void);
+
+/* Idle thread. Executes when no other thread is ready to run. */
static void
idle (void *aux UNUSED)
{
for (;;)
{
/* Wait for an interrupt. */
+ DEBUG (idle, "idle");
asm ("hlt");
/* Let someone else run. */
}
}
+/* Initializes the threading system and starts an initial thread
+ which is immediately scheduled. Never returns to the caller.
+ The initial thread is named NAME and executes FUNCTION passing
+ AUX as the argument. */
void
thread_init (void)
{
+ ASSERT (intr_get_level () == IF_OFF);
+
+ /* Initialize run queue. */
list_init (&run_queue);
+
+ /* Create idle thread. */
idle_thread = thread_create ("idle", idle, NULL);
+ idle_thread->status = THREAD_BLOCKED;
}
-struct thread_root_frame
+void
+thread_start (void)
+{
+ struct thread *t = find_next_to_run ();
+ if (t->status == THREAD_READY)
+ list_remove (&t->rq_elem);
+ t->status = THREAD_RUNNING;
+ switch_threads (NULL, t);
+
+ NOT_REACHED ();
+}
+\f
+/* Stack frame for kernel_thread(). */
+struct kernel_thread_frame
{
void *eip; /* Return address. */
void (*function) (void *); /* Function to call. */
void *aux; /* Auxiliary data for function. */
};
+/* Function used as the basis for a kernel thread. */
static void
-thread_root (void (*function) (void *aux), void *aux)
+kernel_thread (void (*function) (void *aux), void *aux)
{
ASSERT (function != NULL);
- intr_enable ();
- function (aux);
- thread_exit ();
+ intr_enable (); /* The scheduler runs with interrupts off. */
+ function (aux); /* Execute the thread function. */
+ thread_exit (); /* If function() returns, kill the thread. */
}
+/* Creates a new thread named NAME and initializes its fields.
+ Returns the new thread if successful or a null pointer on
+ failure. */
static struct thread *
new_thread (const char *name)
{
{
strlcpy (t->name, name, sizeof t->name);
t->stack = (uint8_t *) t + PGSIZE;
- t->status = THREAD_BLOCKED;
+ t->status = THREAD_INITIALIZING;
}
return t;
}
+/* Allocates a SIZE-byte frame within thread T's stack and
+ returns a pointer to the frame's base. */
static void *
alloc_frame (struct thread *t, size_t size)
{
+ /* Stack data is always allocated in word-size units. */
ASSERT (size % sizeof (uint32_t) == 0);
t->stack -= size;
return t->stack;
}
+/* Creates a new kernel thread named NAME, which executes
+ FUNCTION passing AUX as the argument. The thread is added to
+ the ready queue. Thus, it may be scheduled even before
+ thread_create() returns. If you need to ensure ordering, then
+ use synchronization, such as a semaphore. */
struct thread *
thread_create (const char *name, void (*function) (void *aux), void *aux)
{
struct thread *t;
- struct thread_root_frame *rf;
+ struct kernel_thread_frame *kf;
struct switch_entry_frame *ef;
struct switch_threads_frame *sf;
t = new_thread (name);
- /* Stack frame for thread_root(). */
- rf = alloc_frame (t, sizeof *rf);
- rf->eip = NULL;
- rf->function = function;
- rf->aux = aux;
+ /* Stack frame for kernel_thread(). */
+ kf = alloc_frame (t, sizeof *kf);
+ kf->eip = NULL;
+ kf->function = function;
+ kf->aux = aux;
/* Stack frame for switch_entry(). */
ef = alloc_frame (t, sizeof *ef);
- ef->eip = (void (*) (void)) thread_root;
+ ef->eip = (void (*) (void)) kernel_thread;
- /* Stack frame for thread_switch(). */
+ /* Stack frame for switch_threads(). */
sf = alloc_frame (t, sizeof *sf);
sf->eip = switch_entry;
return false;
if (!addrspace_load (&t->addrspace, filename, &start))
- panic ("%s: program load failed", filename);
+ PANIC ("%s: program load failed", filename);
/* Interrupt frame. */
if_ = alloc_frame (t, sizeof *if_);
ef = alloc_frame (t, sizeof *ef);
ef->eip = intr_exit;
- /* Stack frame for thread_switch(). */
+ /* Stack frame for switch_threads(). */
sf = alloc_frame (t, sizeof *sf);
sf->eip = switch_entry;
find_next_to_run (void)
{
if (list_empty (&run_queue))
- return NULL;
+ return idle_thread;
else
return list_entry (list_pop_front (&run_queue), struct thread, rq_elem);
}
void
schedule_tail (struct thread *prev)
{
- struct thread *cur = thread_current ();
-
ASSERT (intr_get_level () == IF_OFF);
#ifdef USERPROG
- addrspace_activate (&cur->addrspace);
+ addrspace_activate (&thread_current ()->addrspace);
#endif
if (prev != NULL && prev->status == THREAD_DYING)
ASSERT (cur->status != THREAD_RUNNING);
next = find_next_to_run ();
- if (next == NULL)
- next = idle_thread;
next->status = THREAD_RUNNING;
if (cur != next)
intr_set_level (old_level);
}
-void
-thread_start (struct thread *t)
-{
- ASSERT (intr_get_level () == IF_OFF);
-
- if (t->status == THREAD_READY)
- list_remove (&t->rq_elem);
- t->status = THREAD_RUNNING;
- switch_threads (NULL, t);
- NOT_REACHED ();
-}
-
void
thread_exit (void)
{
thread_current ()->status = THREAD_BLOCKED;
thread_schedule ();
}
-
-static void
-tfunc (void *aux UNUSED)
-{
- for (;;)
- {
- size_t count, i;
- if (random_ulong () % 5 == 0)
- {
- printk ("%s exiting\n", thread_current ()->name);
- break;
- }
- count = random_ulong () % 25 * 10000;
- printk ("%s waiting %zu: ", thread_current ()->name, count);
- for (i = 0; i < count; i++);
- printk ("%s\n", thread_current ()->name);
- }
-}
-
-void
-thread_self_test (void)
-{
- struct thread *t;
- int i;
-
- for (i = 0; i < 4; i++)
- {
- char name[2];
- name[0] = 'a' + i;
- name[1] = 0;
- t = thread_create (name, tfunc, NULL);
- }
- thread_start (t);
-}
projects / pintos-anon / blobdiff