#include "thread.h"
#include <stddef.h>
-#include "debug.h"
#include "interrupt.h"
#include "intr-stubs.h"
-#include "lib.h"
-#include "gdt.h"
#include "mmu.h"
#include "palloc.h"
-#include "random.h"
#include "switch.h"
+#include "lib/debug.h"
+#include "lib/lib.h"
+#include "lib/random.h"
+#ifdef USERPROG
+#include "userprog/gdt.h"
+#endif
+/* Value for struct thread's `magic' member.
+ Used to detect stack overflow. See the big comment at the top
+ of thread.h for details. */
#define THREAD_MAGIC 0x1234abcdu
/* List of processes in THREAD_READY state, that is, processes
static void kernel_thread (thread_func *, void *aux);
+static struct thread *running_thread (void);
static struct thread *next_thread_to_run (void);
static struct thread *new_thread (const char *name);
-static bool is_thread (struct thread *t);
-static void *alloc_frame (struct thread *t, size_t size);
-static void destroy_thread (struct thread *t);
+static void init_thread (struct thread *, const char *name);
+static bool is_thread (struct thread *);
+static void *alloc_frame (struct thread *, size_t size);
+static void destroy_thread (struct thread *);
static void schedule (void);
void schedule_tail (struct thread *prev);
-/* Initializes the threading system. After calling, create some
- threads with thread_create() or thread_execute(), then start
- the scheduler with thread_start(). */
+/* Initializes the threading system by transforming the code
+ that's currently running into a thread. Note that this is
+ possible only because the loader was careful to put the bottom
+ of the stack at a page boundary; it won't work in general.
+ Also initializes the run queue.
+
+ After calling this function, be sure to initialize the page
+ allocator before trying to create any threads with
+ thread_create(). */
void
thread_init (void)
{
+ struct thread *t;
+
ASSERT (intr_get_level () == INTR_OFF);
+ /* Set up a thread structure for the running thread. */
+ t = running_thread ();
+ init_thread (t, "main");
+ t->status = THREAD_RUNNING;
+
/* Initialize run queue. */
list_init (&run_queue);
-
- /* Create idle thread. */
- idle_thread = thread_create ("idle", idle, NULL);
- idle_thread->status = THREAD_BLOCKED;
}
-/* Starts the thread scheduler. The caller should have created
- some threads with thread_create() or thread_execute(). Never
- returns to the caller. */
+/* Starts preemptive thread scheduling by enabling interrupts.
+ Also creates the idle thread. */
void
thread_start (void)
{
- struct thread *t = next_thread_to_run ();
- if (t->status == THREAD_READY)
- list_remove (&t->rq_elem);
- t->status = THREAD_RUNNING;
- switch_threads (NULL, t);
+ /* Create idle thread. */
+ idle_thread = thread_create ("idle", idle, NULL);
+ idle_thread->status = THREAD_BLOCKED;
- NOT_REACHED ();
+ /* Enable interrupts. */
+ intr_enable ();
}
/* Creates a new kernel thread named NAME, which executes
sf->eip = switch_entry;
/* Add to run queue. */
- thread_wake (t);
+ thread_unblock (t);
return t;
}
sf->eip = switch_entry;
/* Add to run queue. */
- thread_wake (t);
+ thread_unblock (t);
return true;
}
#endif
-/* Transitions T from its current state to THREAD_READY, the
- ready-to-run state. On entry, T must be ready or blocked.
+/* Transitions a blocked thread T from its current state to the
+ ready-to-run state. If T is not blocked, there is no effect.
(Use thread_yield() to make the running thread ready.) */
void
-thread_wake (struct thread *t)
+thread_unblock (struct thread *t)
{
+ enum intr_level old_level;
+
ASSERT (is_thread (t));
- ASSERT (t->status == THREAD_READY || t->status == THREAD_BLOCKED);
- if (t->status != THREAD_READY)
+
+ old_level = intr_disable ();
+ if (t->status == THREAD_BLOCKED)
{
- list_push_back (&run_queue, &t->rq_elem);
+ list_push_back (&run_queue, &t->elem);
t->status = THREAD_READY;
}
+ intr_set_level (old_level);
}
/* Returns the name of thread T. */
return t->name;
}
-/* Returns the running thread. */
+/* Returns the running thread.
+ This is running_thread() plus a couple of sanity checks.
+ See the big comment at the top of thread.h for details. */
struct thread *
thread_current (void)
{
- uint32_t *esp;
- struct thread *t;
-
- /* Copy the CPU's stack pointer into `esp', and then round that
- down to the start of a page. Because `struct thread' is
- always at the beginning of a page and the stack pointer is
- somewhere in the middle, this locates the curent thread. */
- asm ("movl %%esp, %0\n" : "=g" (esp));
- t = pg_round_down (esp);
-
+ struct thread *t = running_thread ();
+
/* Make sure T is really a thread.
- If this assertion fires, then your thread may have
- overflowed its stack. Each thread has less than 4 kB of
- stack, so a few big automatic arrays or moderate recursion
- can cause stack overflow. */
+ If either of these assertions fire, then your thread may
+ have overflowed its stack. Each thread has less than 4 kB
+ of stack, so a few big automatic arrays or moderate
+ recursion can cause stack overflow. */
ASSERT (is_thread (t));
+ ASSERT (t->status == THREAD_RUNNING);
return t;
}
{
ASSERT (!intr_context ());
+ /* Just set our status to dying and schedule another process.
+ We will be destroyed during the call to schedule_tail(). */
intr_disable ();
thread_current ()->status = THREAD_DYING;
schedule ();
ASSERT (!intr_context ());
old_level = intr_disable ();
- list_push_back (&run_queue, &cur->rq_elem);
+ list_push_back (&run_queue, &cur->elem);
cur->status = THREAD_READY;
schedule ();
intr_set_level (old_level);
}
/* Puts the current thread to sleep. It will not be scheduled
- again until awoken by thread_wake(). */
+ again until awoken by thread_unblock().
+
+ This function must be called with interrupts turned off. It
+ is usually a better idea to use one of the synchronization
+ primitives in synch.h. */
void
-thread_sleep (void)
+thread_block (void)
{
ASSERT (!intr_context ());
ASSERT (intr_get_level () == INTR_OFF);
/* Let someone else run. */
intr_disable ();
- thread_sleep ();
+ thread_block ();
intr_enable ();
}
}
thread_exit (); /* If function() returns, kill the thread. */
}
\f
+/* Returns the running thread. */
+struct thread *
+running_thread (void)
+{
+ uint32_t *esp;
+
+ /* Copy the CPU's stack pointer into `esp', and then round that
+ down to the start of a page. Because `struct thread' is
+ always at the beginning of a page and the stack pointer is
+ somewhere in the middle, this locates the curent thread. */
+ asm ("movl %%esp, %0\n" : "=g" (esp));
+ return pg_round_down (esp);
+}
+
/* Returns true if T appears to point to a valid thread. */
static bool
is_thread (struct thread *t)
t = palloc_get (PAL_ZERO);
if (t != NULL)
- {
- strlcpy (t->name, name, sizeof t->name);
- t->stack = (uint8_t *) t + PGSIZE;
- t->status = THREAD_BLOCKED;
- t->magic = THREAD_MAGIC;
- }
-
+ init_thread (t, name);
+
return t;
}
+/* Initializes T as a new, blocked thread named NAME. */
+static void
+init_thread (struct thread *t, const char *name)
+{
+ memset (t, 0, sizeof *t);
+ strlcpy (t->name, name, sizeof t->name);
+ t->stack = (uint8_t *) t + PGSIZE;
+ t->status = THREAD_BLOCKED;
+ t->magic = THREAD_MAGIC;
+}
+
/* Allocates a SIZE-byte frame at the top of thread T's stack and
returns a pointer to the frame's base. */
static void *
if (list_empty (&run_queue))
return idle_thread;
else
- return list_entry (list_pop_front (&run_queue), struct thread, rq_elem);
+ return list_entry (list_pop_front (&run_queue), struct thread, elem);
}
/* Destroys T, which must be in the dying state and must not be
void
schedule_tail (struct thread *prev)
{
- struct thread *cur = thread_current ();
+ struct thread *cur = running_thread ();
ASSERT (intr_get_level () == INTR_OFF);
+ /* Mark us as running. */
cur->status = THREAD_RUNNING;
- if (prev != NULL && prev->status == THREAD_DYING)
- destroy_thread (prev);
#ifdef USERPROG
+ /* Activate the new address space. */
addrspace_activate (cur);
#endif
+
+ /* If the thread we switched from is dying, destroy it.
+ This must happen late because it's not a good idea to
+ e.g. destroy the page table you're currently using. */
+ if (prev != NULL && prev->status == THREAD_DYING)
+ destroy_thread (prev);
}
/* Schedules a new process. At entry, interrupts must be off and
static void
schedule (void)
{
- struct thread *cur = thread_current ();
+ struct thread *cur = running_thread ();
struct thread *next = next_thread_to_run ();
+ struct thread *prev = NULL;
ASSERT (intr_get_level () == INTR_OFF);
ASSERT (cur->status != THREAD_RUNNING);
ASSERT (is_thread (next));
if (cur != next)
- {
- struct thread *prev = switch_threads (cur, next);
- schedule_tail (prev);
- }
+ prev = switch_threads (cur, next);
+ schedule_tail (prev);
}
\f
/* Offset of `stack' member within `struct thread'.
projects / pintos-anon / blobdiff