pthread.c

Newlib 嵌入式 C库 标准实现代码

      mask with e.g. sigsetjmp before creating the first thread);
   - a regular function called from pthread_create when needed. */

static void pthread_initialize(void) __attribute__((constructor));

#ifndef HAVE_Z_NODELETE
extern void *__dso_handle __attribute__ ((weak));
#endif


/* Do some minimal initialization which has to be done during the
   startup of the C library.  */
void
__pthread_initialize_minimal(void)
{
  /* If we have special thread_self processing, initialize that for the
     main thread now.  */
#ifdef INIT_THREAD_SELF
  INIT_THREAD_SELF(&__pthread_initial_thread, 0);
#endif
#if HP_TIMING_AVAIL
  __pthread_initial_thread.p_cpuclock_offset = _dl_cpuclock_offset;
#endif
}


void
__pthread_init_max_stacksize(void)
{
  struct rlimit limit;
  size_t max_stack;

  getrlimit(RLIMIT_STACK, &limit);
#ifdef FLOATING_STACKS
  if (limit.rlim_cur == RLIM_INFINITY)
    limit.rlim_cur = ARCH_STACK_MAX_SIZE;
# ifdef NEED_SEPARATE_REGISTER_STACK
  max_stack = limit.rlim_cur / 2;
# else
  max_stack = limit.rlim_cur;
# endif
#else
  /* Play with the stack size limit to make sure that no stack ever grows
     beyond STACK_SIZE minus one page (to act as a guard page). */
# ifdef NEED_SEPARATE_REGISTER_STACK
  /* STACK_SIZE bytes hold both the main stack and register backing
     store. The rlimit value applies to each individually.  */
  max_stack = STACK_SIZE/2 - __getpagesize ();
# else
  max_stack = STACK_SIZE - __getpagesize();
# endif
  if (limit.rlim_cur > max_stack) {
    limit.rlim_cur = max_stack;
    __libc_setrlimit(RLIMIT_STACK, &limit);
  }
#endif
  __pthread_max_stacksize = max_stack;
}


static void pthread_initialize(void)
{
  struct sigaction sa;
  sigset_t mask;

  /* If already done (e.g. by a constructor called earlier!), bail out */
  if (__pthread_initial_thread_bos != NULL) return;
#ifdef TEST_FOR_COMPARE_AND_SWAP
  /* Test if compare-and-swap is available */
  __pthread_has_cas = compare_and_swap_is_available();
#endif
#ifdef FLOATING_STACKS
  /* We don't need to know the bottom of the stack.  Give the pointer some
     value to signal that initialization happened.  */
  __pthread_initial_thread_bos = (void *) -1l;
#else
  /* Determine stack size limits .  */
  __pthread_init_max_stacksize ();
# ifdef _STACK_GROWS_UP
  /* The initial thread already has all the stack it needs */
  __pthread_initial_thread_bos = (char *)
    ((long)CURRENT_STACK_FRAME &~ (STACK_SIZE - 1));
# else
  /* For the initial stack, reserve at least STACK_SIZE bytes of stack
     below the current stack address, and align that on a
     STACK_SIZE boundary. */
  __pthread_initial_thread_bos =
    (char *)(((long)CURRENT_STACK_FRAME - 2 * STACK_SIZE) & ~(STACK_SIZE - 1));
# endif
#endif
  /* Update the descriptor for the initial thread. */
  __pthread_initial_thread.p_pid = __getpid();
  /* Likewise for the resolver state _res.  */
  __pthread_initial_thread.p_resp = &_res;
#ifdef __SIGRTMIN
  /* Initialize real-time signals. */
  init_rtsigs ();
#endif
  /* Setup signal handlers for the initial thread.
     Since signal handlers are shared between threads, these settings
     will be inherited by all other threads. */
  sa.sa_handler = pthread_handle_sigrestart;
  sigemptyset(&sa.sa_mask);
  sa.sa_flags = 0;
  __libc_sigaction(__pthread_sig_restart, &sa, NULL);
  sa.sa_handler = pthread_handle_sigcancel;
  // sa.sa_flags = 0;
  __libc_sigaction(__pthread_sig_cancel, &sa, NULL);
  if (__pthread_sig_debug > 0) {
    sa.sa_handler = pthread_handle_sigdebug;
    sigemptyset(&sa.sa_mask);
    // sa.sa_flags = 0;
    __libc_sigaction(__pthread_sig_debug, &sa, NULL);
  }
  /* Initially, block __pthread_sig_restart. Will be unblocked on demand. */
  sigemptyset(&mask);
  sigaddset(&mask, __pthread_sig_restart);
  sigprocmask(SIG_BLOCK, &mask, NULL);
  /* Register an exit function to kill all other threads. */
  /* Do it early so that user-registered atexit functions are called
     before pthread_*exit_process. */
#ifndef HAVE_Z_NODELETE
  if (__builtin_expect (&__dso_handle != NULL, 1))
    __cxa_atexit ((void (*) (void *)) pthread_atexit_process, NULL,
		  __dso_handle);
  else
#endif
    on_exit (pthread_onexit_process, NULL);
  /* How many processors.  */
  __pthread_smp_kernel = is_smp_system ();
}

void __pthread_initialize(void)
{
  pthread_initialize();
}

int __pthread_initialize_manager(void)
{
  int manager_pipe[2];
  int pid;
  struct pthread_request request;

#ifndef HAVE_Z_NODELETE
  if (__builtin_expect (&__dso_handle != NULL, 1))
    __cxa_atexit ((void (*) (void *)) pthread_atexit_retcode, NULL,
		  __dso_handle);
#endif

  if (__pthread_max_stacksize == 0)
    __pthread_init_max_stacksize ();
  /* If basic initialization not done yet (e.g. we're called from a
     constructor run before our constructor), do it now */
  if (__pthread_initial_thread_bos == NULL) pthread_initialize();
  /* Setup stack for thread manager */
  __pthread_manager_thread_bos = malloc(THREAD_MANAGER_STACK_SIZE);
  if (__pthread_manager_thread_bos == NULL) return -1;
  __pthread_manager_thread_tos =
    __pthread_manager_thread_bos + THREAD_MANAGER_STACK_SIZE;
  /* Setup pipe to communicate with thread manager */
  if (__libc_pipe(manager_pipe) == -1) {
    free(__pthread_manager_thread_bos);
    return -1;
  }
  /* Start the thread manager */
  pid = 0;
  if (__builtin_expect (__pthread_initial_thread.p_report_events, 0))
    {
      /* It's a bit more complicated.  We have to report the creation of
	 the manager thread.  */
      int idx = __td_eventword (TD_CREATE);
      uint32_t mask = __td_eventmask (TD_CREATE);

      if ((mask & (__pthread_threads_events.event_bits[idx]
		   | __pthread_initial_thread.p_eventbuf.eventmask.event_bits[idx]))
	  != 0)
	{
	  __pthread_lock(__pthread_manager_thread.p_lock, NULL);

#ifdef NEED_SEPARATE_REGISTER_STACK
	  pid = __clone2(__pthread_manager_event,
			 (void **) __pthread_manager_thread_bos,
			 THREAD_MANAGER_STACK_SIZE,
			 CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND,
			 (void *)(long)manager_pipe[0]);
#elif _STACK_GROWS_UP
	  pid = __clone(__pthread_manager_event,
			(void **) __pthread_manager_thread_bos,
			CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND,
			(void *)(long)manager_pipe[0]);
#else
	  pid = __clone(__pthread_manager_event,
			(void **) __pthread_manager_thread_tos,
			CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND,
			(void *)(long)manager_pipe[0]);
#endif

	  if (pid != -1)
	    {
	      /* Now fill in the information about the new thread in
	         the newly created thread's data structure.  We cannot let
	         the new thread do this since we don't know whether it was
	         already scheduled when we send the event.  */
	      __pthread_manager_thread.p_eventbuf.eventdata =
		&__pthread_manager_thread;
	      __pthread_manager_thread.p_eventbuf.eventnum = TD_CREATE;
	      __pthread_last_event = &__pthread_manager_thread;
	      __pthread_manager_thread.p_tid = 2* PTHREAD_THREADS_MAX + 1;
	      __pthread_manager_thread.p_pid = pid;

	      /* Now call the function which signals the event.  */
	      __linuxthreads_create_event ();
	    }

	  /* Now restart the thread.  */
	  __pthread_unlock(__pthread_manager_thread.p_lock);
	}
    }

  if (__builtin_expect (pid, 0) == 0)
    {
#ifdef NEED_SEPARATE_REGISTER_STACK
      pid = __clone2(__pthread_manager, (void **) __pthread_manager_thread_bos,
		     THREAD_MANAGER_STACK_SIZE,
		     CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND,
		     (void *)(long)manager_pipe[0]);
#elif _STACK_GROWS_UP
      pid = __clone(__pthread_manager, (void **) __pthread_manager_thread_bos,
		    CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND,
		    (void *)(long)manager_pipe[0]);
#else
      pid = __clone(__pthread_manager, (void **) __pthread_manager_thread_tos,
		    CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND,
		    (void *)(long)manager_pipe[0]);
#endif
    }
  if (__builtin_expect (pid, 0) == -1) {
    free(__pthread_manager_thread_bos);
    __libc_close(manager_pipe[0]);
    __libc_close(manager_pipe[1]);
    return -1;
  }
  __pthread_manager_request = manager_pipe[1]; /* writing end */
  __pthread_manager_reader = manager_pipe[0]; /* reading end */
  __pthread_manager_thread.p_tid = 2* PTHREAD_THREADS_MAX + 1;
  __pthread_manager_thread.p_pid = pid;
  /* Make gdb aware of new thread manager */
  if (__builtin_expect (__pthread_threads_debug, 0) && __pthread_sig_debug > 0)
    {
      raise(__pthread_sig_debug);
      /* We suspend ourself and gdb will wake us up when it is
	 ready to handle us. */
      __pthread_wait_for_restart_signal(thread_self());
    }
  /* Synchronize debugging of the thread manager */
  request.req_kind = REQ_DEBUG;
  TEMP_FAILURE_RETRY(__libc_write(__pthread_manager_request,
				  (char *) &request, sizeof(request)));
  return 0;
}

/* Thread creation */

int __pthread_create_2_1(pthread_t *thread, const pthread_attr_t *attr,
			 void * (*start_routine)(void *), void *arg)
{
  pthread_descr self = thread_self();
  struct pthread_request request;
  int retval;
  if (__builtin_expect (__pthread_manager_request, 0) < 0) {
    if (__pthread_initialize_manager() < 0) return EAGAIN;
  }
  request.req_thread = self;
  request.req_kind = REQ_CREATE;
  request.req_args.create.attr = attr;
  request.req_args.create.fn = start_routine;
  request.req_args.create.arg = arg;
  sigprocmask(SIG_SETMASK, (const sigset_t *) NULL,
              &request.req_args.create.mask);
  TEMP_FAILURE_RETRY(__libc_write(__pthread_manager_request,
				  (char *) &request, sizeof(request)));
  suspend(self);
  retval = THREAD_GETMEM(self, p_retcode);
  if (__builtin_expect (retval, 0) == 0)
    *thread = (pthread_t) THREAD_GETMEM(self, p_retval);
  return retval;
}

versioned_symbol (libpthread, __pthread_create_2_1, pthread_create, GLIBC_2_1);

#if SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_1)

int __pthread_create_2_0(pthread_t *thread, const pthread_attr_t *attr,
			 void * (*start_routine)(void *), void *arg)
{
  /* The ATTR attribute is not really of type `pthread_attr_t *'.  It has
     the old size and access to the new members might crash the program.
     We convert the struct now.  */
  pthread_attr_t new_attr;

  if (attr != NULL)
    {
      size_t ps = __getpagesize ();

      memcpy (&new_attr, attr,
	      (size_t) &(((pthread_attr_t*)NULL)->__guardsize));
      new_attr.__guardsize = ps;
      new_attr.__stackaddr_set = 0;
      new_attr.__stackaddr = NULL;
      new_attr.__stacksize = STACK_SIZE - ps;
      attr = &new_attr;
    }
  return __pthread_create_2_1 (thread, attr, start_routine, arg);
}
compat_symbol (libpthread, __pthread_create_2_0, pthread_create, GLIBC_2_0);
#endif

/* Simple operations on thread identifiers */

pthread_t pthread_self(void)
{
  pthread_descr self = thread_self();
  return THREAD_GETMEM(self, p_tid);
}

int pthread_equal(pthread_t thread1, pthread_t thread2)
{
  return thread1 == thread2;
}

/* Helper function for thread_self in the case of user-provided stacks */

#ifndef THREAD_SELF

pthread_descr __pthread_find_self(void)
{
  char * sp = CURRENT_STACK_FRAME;
  pthread_handle h;

  /* __pthread_handles[0] is the initial thread, __pthread_handles[1] is
     the manager threads handled specially in thread_self(), so start at 2 */
  h = __pthread_handles + 2;
  while (! (sp <= (char *) h->h_descr && sp >= h->h_bottom)) h++;
  return h->h_descr;
}

#else

static pthread_descr thread_self_stack(void)
{
  char *sp = CURRENT_STACK_FRAME;
  pthread_handle h;

  if (sp >= __pthread_manager_thread_bos && sp < __pthread_manager_thread_tos)
    return &__pthread_manager_thread;
  h = __pthread_handles + 2;
  while (! (sp <= (char *) h->h_descr && sp >= h->h_bottom))
    h++;
  return h->h_descr;
}

#endif

/* Thread scheduling */

int pthread_setschedparam(pthread_t thread, int policy,
                          const struct sched_param *param)
{
  pthread_handle handle = thread_handle(thread);
  pthread_descr th;

  __pthread_lock(&handle->h_lock, NULL);
  if (__builtin_expect (invalid_handle(handle, thread), 0)) {
    __pthread_unlock(&handle->h_lock);
    return ESRCH;
  }
  th = handle->h_descr;
  if (__builtin_expect (__sched_setscheduler(th->p_pid, policy, param) == -1,
			0)) {
    __pthread_unlock(&handle->h_lock);
    return errno;
  }
  th->p_priority = policy == SCHED_OTHER ? 0 : param->sched_priority;
  __pthread_unlock(&handle->h_lock);
  if (__pthread_manager_request >= 0)
    __pthread_manager_adjust_prio(th->p_priority);
  return 0;
}

int pthread_getschedparam(pthread_t thread, int *policy,
                          struct sched_param *param)
{
  pthread_handle handle = thread_handle(thread);
  int pid, pol;

  __pthread_lock(&handle->h_lock, NULL);
  if (__builtin_expect (invalid_handle(handle, thread), 0)) {
    __pthread_unlock(&handle->h_lock);
    return ESRCH;
  }
  pid = handle->h_descr->p_pid;
  __pthread_unlock(&handle->h_lock);
  pol = __sched_getscheduler(pid);
  if (__builtin_expect (pol, 0) == -1) return errno;
  if (__sched_getparam(pid, param) == -1) return errno;
  *policy = pol;
  return 0;
}

int __pthread_yield (void)
{
  /* For now this is equivalent with the POSIX call.  */
  return sched_yield ();
}
weak_alias (__pthread_yield, pthread_yield)

/* Process-wide exit() request */