minix/lib/libmthread/allocate.c

#define ALLOCATE
#include <errno.h>
#include <minix/mthread.h>
#include "global.h"
#include "proto.h"

#define FALLBACK_CTX (&(fallback.m_context))

FORWARD _PROTOTYPE( void mthread_fallback, (void)			);
FORWARD _PROTOTYPE( int mthread_increase_thread_pool, (void)			);
FORWARD _PROTOTYPE( void mthread_thread_init, (mthread_thread_t thread,
					       mthread_attr_t *tattr,
					       void (*proc)(void *),
					       void *arg)		);

FORWARD _PROTOTYPE( void mthread_thread_reset, (mthread_thread_t thread));
FORWARD _PROTOTYPE( void mthread_thread_stop, (mthread_thread_t thread));
FORWARD _PROTOTYPE( void mthread_trampoline, (void)			);

PRIVATE int initialized = 0;

PRIVATE struct __mthread_attr default_attr = {	MTHREAD_STACK_MIN,
						NULL,
						MTHREAD_CREATE_JOINABLE,
						NULL, NULL };

/*===========================================================================*
 *				mthread_equal				     *
 *===========================================================================*/
PUBLIC int mthread_equal(l, r)
mthread_thread_t l;
mthread_thread_t r;
{
/* Compare two thread ids */
  mthread_init();	/* Make sure mthreads is initialized */

  return(l == r);
}


/*===========================================================================*
 *				mthread_create				     *
 *===========================================================================*/
PUBLIC int mthread_create(threadid, tattr, proc, arg)
mthread_thread_t *threadid;
mthread_attr_t *tattr;
void (*proc)(void *);
void *arg;
{
/* Register procedure proc for execution in a thread. */
  mthread_thread_t thread;

  mthread_init();	/* Make sure mthreads is initialized */

  if (proc == NULL) {
  	errno = EINVAL;
  	return(-1);
  }

  if (!mthread_queue_isempty(&free_threads)) {
  	thread = mthread_queue_remove(&free_threads);
  	mthread_thread_init(thread, tattr, proc, arg);
 	used_threads++;
 	if(threadid != NULL) 
 		*threadid = (mthread_thread_t) thread;
#ifdef MDEBUG
 	printf("Inited thread %d\n", thread);
#endif
 	return(0);
  } else  {
  	if (mthread_increase_thread_pool() == -1) {
  		errno = EAGAIN;
  		return(-1);
  	}

  	return mthread_create(threadid, tattr, proc, arg);
  }
}


/*===========================================================================*
 *				mthread_detach				     *
 *===========================================================================*/
PUBLIC int mthread_detach(detach)
mthread_thread_t detach;
{
/* Mark a thread as detached. Consequently, upon exit, resources allocated for
 * this thread are automatically freed.
 */

  mthread_init();	/* Make sure mthreads is initialized */

  if (!isokthreadid(detach)) {
  	errno = ESRCH;
  	return(-1);
  } else if (threads[detach].m_state == DEAD) {
  	errno = ESRCH;
  	return(-1);
  } else if (threads[detach].m_attr.a_detachstate != MTHREAD_CREATE_DETACHED) {
  	if (threads[detach].m_state == EXITING) {
  		mthread_thread_stop(detach);
  	} else {
		threads[detach].m_attr.a_detachstate = MTHREAD_CREATE_DETACHED;
	}
  }
  return(0);
}


/*===========================================================================*
 *				mthread_exit				     *
 *===========================================================================*/
PUBLIC void mthread_exit(value)
void *value;
{
/* Make a thread stop running and store the result value. */
  int fallback_exit = 0;
  mthread_thread_t stop;

  mthread_init();	/* Make sure mthreads is initialized */

  stop = current_thread;

  if (threads[stop].m_state == EXITING) /* Already stopping, nothing to do. */
  	return;

  /* When we're called from the fallback thread, the fallback thread 
   * will invoke the scheduler. However, if the thread itself called 
   * mthread_exit, _we_ will have to wake up the scheduler.
   */
  if (threads[stop].m_state == FALLBACK_EXITING)
  	fallback_exit = 1;

  threads[stop].m_result = value;
  threads[stop].m_state = EXITING;

  if (threads[stop].m_attr.a_detachstate == MTHREAD_CREATE_DETACHED) {
	mthread_thread_stop(stop);
  } else {
  	/* Joinable thread; notify possibly waiting thread */
	if (mthread_cond_signal(&(threads[stop].m_exited)) != 0) 
		mthread_panic("Couldn't signal exit");

	/* The thread that's actually doing the join will eventually clean
	 * up this thread (i.e., call mthread_thread_stop).
	 */
  }

  /* The fallback thread does a mthread_schedule. If we're not running from
   * that thread, we have to do it ourselves.
   */
  if (!fallback_exit) 
	mthread_schedule();

}


/*===========================================================================*
 *				mthread_fallback			     *
 *===========================================================================*/
PRIVATE void mthread_fallback(void)
{
/* The mthreads fallback thread. The idea is that every thread calls 
 * mthread_exit(...) to stop running when it has nothing to do anymore. 
 * However, in case a thread forgets to do that, the whole process  exit()s and
 * that might be a bit problematic. Therefore, all threads will run this
 * fallback thread when they exit, giving the scheduler a chance to fix the
 * situation.
 */

  threads[current_thread].m_state = FALLBACK_EXITING;
  mthread_exit(NULL);

  /* Reconstruct fallback context for next invocation */
  makecontext(FALLBACK_CTX, (void (*) (void)) mthread_fallback, 0);

  /* Let another thread run */
  mthread_schedule();

}


/*===========================================================================*
 *			mthread_increase_thread_pool			     *
 *===========================================================================*/
PRIVATE int mthread_increase_thread_pool(void)
{
/* Increase thread pool. No fancy algorithms, just double the size. */
  mthread_tcb_t *new_tcb;
  int new_no_threads, old_no_threads, i;

  old_no_threads = no_threads;
  new_no_threads = 2 * old_no_threads;

  if (new_no_threads >= MAX_THREAD_POOL) {
  	mthread_debug("Reached max number of threads");
  	return(-1);
  }

  new_tcb = realloc(threads, new_no_threads * sizeof(mthread_tcb_t));
  if (new_tcb == NULL) {
  	mthread_debug("Can't increase thread pool");
  	return(-1);
  }

  threads = new_tcb; 
  no_threads = new_no_threads;

  /* Add newly available threads to free_threads */
  for (i = old_no_threads; i < new_no_threads; i++) {
	mthread_queue_add(&free_threads, i);
	mthread_thread_reset(i);
  }

#ifdef MDEBUG
  printf("Increased thread pool from %d to %d threads\n", no_threads, new_no_threads);
#endif
  return(0);
}


/*===========================================================================*
 *				mthread_init				     *
 *===========================================================================*/
PUBLIC void mthread_init(void)
{
/* Initialize thread system; allocate thread structures and start creating
 * threads.
 */

  if (!initialized) {
  	int i;
  	no_threads = NO_THREADS;
  	used_threads = 0;
  	running_main_thread = 1;/* mthread_init can only be called from the
  				 * main thread. Calling it from a thread will
  				 * not enter this clause.
  				 */

  	if (getcontext(&(mainthread.m_context)) == -1)
  		mthread_panic("Couldn't save state for main thread");
  	current_thread = NO_THREAD;

	/* Allocate a bunch of thread control blocks */
	threads = malloc(no_threads * sizeof(mthread_tcb_t));
	if (threads == NULL)
		mthread_panic("No memory, can't initialize threads");

	mthread_init_valid_mutexes();
	mthread_init_valid_conditions();
	mthread_init_valid_attributes();
	mthread_init_scheduler();

	/* Put initial threads on the free threads queue */
	mthread_queue_init(&free_threads);
	for (i = 0; i < no_threads; i++) {
		mthread_queue_add(&free_threads, i);
		mthread_thread_reset(i);
	}

	/* Initialize the fallback thread */
	if (getcontext(FALLBACK_CTX) == -1)
		mthread_panic("Could not initialize fallback thread");
	FALLBACK_CTX->uc_link = &(mainthread.m_context);
	FALLBACK_CTX->uc_stack.ss_sp = malloc(STACKSZ);
	FALLBACK_CTX->uc_stack.ss_size = STACKSZ;
	if (FALLBACK_CTX->uc_stack.ss_sp == NULL)
		mthread_panic("Could not allocate stack space to fallback "
			      "thread");
  	makecontext(FALLBACK_CTX, (void (*) (void)) mthread_fallback, 0);

	initialized = 1;
  }
}


/*===========================================================================*
 *				mthread_join				     *
 *===========================================================================*/
PUBLIC int mthread_join(join, value)
mthread_thread_t join;
void **value;
{
/* Wait for a thread to stop running and copy the result. */

  mthread_init();	/* Make sure mthreads is initialized */

  if (!isokthreadid(join)) {
  	errno = ESRCH;
  	return(-1);
  } else if (join == current_thread) {
	errno = EDEADLK;
	return(-1);
  } else if (threads[join].m_state == DEAD) {
  	errno = ESRCH;
  	return(-1);
  } else if (threads[join].m_attr.a_detachstate == MTHREAD_CREATE_DETACHED) {
	errno = EINVAL;
	return(-1);
  }

  /* When the thread hasn't exited yet, we have to wait for that to happen */
  if (threads[join].m_state != EXITING) {
  	mthread_cond_t *c;
  	mthread_mutex_t *m;

  	c = &(threads[join].m_exited);
  	m = &(threads[join].m_exitm);

  	if (mthread_mutex_init(m, NULL) != 0)
		mthread_panic("Couldn't initialize mutex to join\n");

	if (mthread_mutex_lock(m) != 0)
		mthread_panic("Couldn't lock mutex to join\n");

	if (mthread_cond_wait(c, m) != 0) 
		mthread_panic("Couldn't wait for join condition\n");
		
	if (mthread_mutex_unlock(m) != 0)
		mthread_panic("Couldn't unlock mutex to join\n");

	if (mthread_mutex_destroy(m) != 0)
		mthread_panic("Couldn't destroy mutex to join\n");
  }

  /* Thread has exited; copy results */
  if(value != NULL)
	*value = threads[join].m_result;

  /* Deallocate resources */
  mthread_thread_stop(join);
  return(0);
}


/*===========================================================================*
 *				mthread_once				     *
 *===========================================================================*/
PUBLIC int mthread_once(once, proc)
mthread_once_t *once;
void (*proc)(void);
{
/* Run procedure proc just once */

  mthread_init();	/* Make sure mthreads is initialized */

  if (once == NULL || proc == NULL) {
  	errno = EINVAL;
  	return(-1);
  } 

  if (*once != 1) proc();
  *once = 1;
  return(0);
}


/*===========================================================================*
 *				mthread_self				     *
 *===========================================================================*/
PUBLIC mthread_thread_t mthread_self(void)
{
/* Return the thread id of the thread calling this function. */

  mthread_init();	/* Make sure mthreads is initialized */

  return(current_thread);
}


/*===========================================================================*
 *				mthread_thread_init			     *
 *===========================================================================*/
PRIVATE void mthread_thread_init(thread, tattr, proc, arg)
mthread_thread_t thread;
mthread_attr_t *tattr;
void (*proc)(void *);
void *arg;
{
/* Initialize a thread so that it, when unsuspended, will run the given
 * procedure with the given parameter. The thread is marked as runnable.
 */

#define THIS_CTX (&(threads[thread].m_context))
  size_t stacksize;
  char *stackaddr;

  threads[thread].m_next = NO_THREAD;
  threads[thread].m_state = DEAD;
  threads[thread].m_proc = (void *(*)(void *)) proc; /* Yikes */
  threads[thread].m_arg = arg;
  /* Threads use a copy of the provided attributes. This way, if another
   * thread modifies the attributes (such as detach state), already running
   * threads are not affected.
   */
  if (tattr != NULL)
  	threads[thread].m_attr = *((struct __mthread_attr *) *tattr);
  else {
  	threads[thread].m_attr = default_attr;
  }

  if (mthread_cond_init(&(threads[thread].m_exited), NULL) != 0)
  	mthread_panic("Could not initialize thread");

  /* First set the fallback thread, */
  THIS_CTX->uc_link = FALLBACK_CTX;

  /* then construct this thread's context to run procedure proc. */
  if (getcontext(THIS_CTX) == -1)
  	mthread_panic("Failed to initialize context state");

  stacksize = threads[thread].m_attr.a_stacksize;
  stackaddr = threads[thread].m_attr.a_stackaddr;

  if (stacksize == (size_t) 0)
	stacksize = (size_t) MTHREAD_STACK_MIN;

  if (stackaddr == NULL) {
	/* Allocate stack space */
  	THIS_CTX->uc_stack.ss_sp = malloc(stacksize);
	if (THIS_CTX->uc_stack.ss_sp == NULL)
  		mthread_panic("Failed to allocate stack to thread");
  } else
  	THIS_CTX->uc_stack.ss_sp = stackaddr;

  THIS_CTX->uc_stack.ss_size = stacksize;
  makecontext(THIS_CTX, mthread_trampoline, 0);

  mthread_unsuspend(thread); /* Make thread runnable */
}


/*===========================================================================*
 *				mthread_thread_reset			     *
 *===========================================================================*/
PRIVATE void mthread_thread_reset(thread)
mthread_thread_t thread;
{
/* Reset the thread to its default values. Free the allocated stack space. */

  mthread_tcb_t *rt;
  if (!isokthreadid(thread)) mthread_panic("Invalid thread id"); 

  rt = &(threads[thread]);

  rt->m_next = NO_THREAD;
  rt->m_state = DEAD;
  rt->m_proc = NULL;
  rt->m_arg = NULL;
  rt->m_result = NULL;
  rt->m_cond = NULL;
  if (rt->m_context.uc_stack.ss_sp)
  	free(rt->m_context.uc_stack.ss_sp); /* Free allocated stack */
  rt->m_context.uc_stack.ss_sp = NULL;
  rt->m_context.uc_stack.ss_size = 0;
  rt->m_context.uc_link = NULL;
}


/*===========================================================================*
 *				mthread_thread_stop			     *
 *===========================================================================*/
PRIVATE void mthread_thread_stop(thread)
mthread_thread_t thread;
{
/* Stop thread from running. Deallocate resources. */
  mthread_tcb_t *stop_thread;

  if (!isokthreadid(thread)) mthread_panic("Invalid thread id"); 

  stop_thread = &(threads[thread]);

  if (stop_thread->m_state == DEAD) {
  	/* Already DEAD, nothing to do */
  	return;
  }

  mthread_thread_reset(thread);
 
  if (mthread_cond_destroy(&(stop_thread->m_exited)) != 0)
  	mthread_panic("Could not destroy condition at thread deallocation\n");

  used_threads--;
  mthread_queue_add(&free_threads, thread);
}


/*===========================================================================*
 *				mthread_trampoline			     *
 *===========================================================================*/
PRIVATE void mthread_trampoline(void)
{
/* Execute the /current_thread's/ procedure. Store its result. */

  void *r;

  r = (threads[current_thread].m_proc)(threads[current_thread].m_arg);
  mthread_exit(r); 
}