timer_routines.c

glibc 2.9,最新版的C语言库函数

/* Helper code for POSIX timer implementation on NPTL.
   Copyright (C) 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Kaz Kylheku <[e-mail]>.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public License as
   published by the Free Software Foundation; either version 2.1 of the
   License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include <assert.h>
#include <errno.h>
#include <pthread.h>
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <sysdep.h>
#include <time.h>
#include <unistd.h>
#include <sys/syscall.h>

#include "posix-timer.h"
#include <pthreadP.h>


/* Number of threads used.  */
#define THREAD_MAXNODES	16

/* Array containing the descriptors for the used threads.  */
static struct thread_node thread_array[THREAD_MAXNODES];

/* Static array with the structures for all the timers.  */
struct timer_node __timer_array[TIMER_MAX];

/* Global lock to protect operation on the lists.  */
pthread_mutex_t __timer_mutex = PTHREAD_MUTEX_INITIALIZER;

/* Variable to protext initialization.  */
pthread_once_t __timer_init_once_control = PTHREAD_ONCE_INIT;

/* Nonzero if initialization of timer implementation failed.  */
int __timer_init_failed;

/* Node for the thread used to deliver signals.  */
struct thread_node __timer_signal_thread_rclk;

/* Lists to keep free and used timers and threads.  */
struct list_links timer_free_list;
struct list_links thread_free_list;
struct list_links thread_active_list;


#ifdef __NR_rt_sigqueueinfo
extern int __syscall_rt_sigqueueinfo (int, int, siginfo_t *);
#endif


/* List handling functions.  */
static inline void
list_init (struct list_links *list)
{
  list->next = list->prev = list;
}

static inline void
list_append (struct list_links *list, struct list_links *newp)
{
  newp->prev = list->prev;
  newp->next = list;
  list->prev->next = newp;
  list->prev = newp;
}

static inline void
list_insbefore (struct list_links *list, struct list_links *newp)
{
  list_append (list, newp);
}

/*
 * Like list_unlink_ip, except that calling it on a node that
 * is already unlinked is disastrous rather than a noop.
 */

static inline void
list_unlink (struct list_links *list)
{
  struct list_links *lnext = list->next, *lprev = list->prev;

  lnext->prev = lprev;
  lprev->next = lnext;
}

static inline struct list_links *
list_first (struct list_links *list)
{
  return list->next;
}

static inline struct list_links *
list_null (struct list_links *list)
{
  return list;
}

static inline struct list_links *
list_next (struct list_links *list)
{
  return list->next;
}

static inline int
list_isempty (struct list_links *list)
{
  return list->next == list;
}


/* Functions build on top of the list functions.  */
static inline struct thread_node *
thread_links2ptr (struct list_links *list)
{
  return (struct thread_node *) ((char *) list
				 - offsetof (struct thread_node, links));
}

static inline struct timer_node *
timer_links2ptr (struct list_links *list)
{
  return (struct timer_node *) ((char *) list
				- offsetof (struct timer_node, links));
}


/* Initialize a newly allocated thread structure.  */
static void
thread_init (struct thread_node *thread, const pthread_attr_t *attr, clockid_t clock_id)
{
  if (attr != NULL)
    thread->attr = *attr;
  else
    {
      pthread_attr_init (&thread->attr);
      pthread_attr_setdetachstate (&thread->attr, PTHREAD_CREATE_DETACHED);
    }

  thread->exists = 0;
  list_init (&thread->timer_queue);
  pthread_cond_init (&thread->cond, 0);
  thread->current_timer = 0;
  thread->captured = pthread_self ();
  thread->clock_id = clock_id;
}


/* Initialize the global lists, and acquire global resources.  Error
   reporting is done by storing a non-zero value to the global variable
   timer_init_failed.  */
static void
init_module (void)
{
  int i;

  list_init (&timer_free_list);
  list_init (&thread_free_list);
  list_init (&thread_active_list);

  for (i = 0; i < TIMER_MAX; ++i)
    {
      list_append (&timer_free_list, &__timer_array[i].links);
      __timer_array[i].inuse = TIMER_FREE;
    }

  for (i = 0; i < THREAD_MAXNODES; ++i)
    list_append (&thread_free_list, &thread_array[i].links);

  thread_init (&__timer_signal_thread_rclk, 0, CLOCK_REALTIME);
}


/* This is a handler executed in a child process after a fork()
   occurs.  It reinitializes the module, resetting all of the data
   structures to their initial state.  The mutex is initialized in
   case it was locked in the parent process.  */
static void
reinit_after_fork (void)
{
  init_module ();
  pthread_mutex_init (&__timer_mutex, 0);
}


/* Called once form pthread_once in timer_init. This initializes the
   module and ensures that reinit_after_fork will be executed in any
   child process.  */
void
__timer_init_once (void)
{
  init_module ();
  pthread_atfork (0, 0, reinit_after_fork);
}


/* Deinitialize a thread that is about to be deallocated.  */
static void
thread_deinit (struct thread_node *thread)
{
  assert (list_isempty (&thread->timer_queue));
  pthread_cond_destroy (&thread->cond);
}


/* Allocate a thread structure from the global free list.  Global
   mutex lock must be held by caller.  The thread is moved to
   the active list. */
struct thread_node *
__timer_thread_alloc (const pthread_attr_t *desired_attr, clockid_t clock_id)
{
  struct list_links *node = list_first (&thread_free_list);

  if (node != list_null (&thread_free_list))
    {
      struct thread_node *thread = thread_links2ptr (node);
      list_unlink (node);
      thread_init (thread, desired_attr, clock_id);
      list_append (&thread_active_list, node);
      return thread;
    }

  return 0;
}


/* Return a thread structure to the global free list.  Global lock
   must be held by caller.  */
void
__timer_thread_dealloc (struct thread_node *thread)
{
  thread_deinit (thread);
  list_unlink (&thread->links);
  list_append (&thread_free_list, &thread->links);
}


/* Each of our threads which terminates executes this cleanup
   handler. We never terminate threads ourselves; if a thread gets here
   it means that the evil application has killed it.  If the thread has
   timers, these require servicing and so we must hire a replacement
   thread right away.  We must also unblock another thread that may
   have been waiting for this thread to finish servicing a timer (see
   timer_delete()).  */

static void
thread_cleanup (void *val)
{
  if (val != NULL)
    {
      struct thread_node *thread = val;

      /* How did the signal thread get killed?  */
      assert (thread != &__timer_signal_thread_rclk);

      pthread_mutex_lock (&__timer_mutex);

      thread->exists = 0;

      /* We are no longer processing a timer event.  */
      thread->current_timer = 0;

      if (list_isempty (&thread->timer_queue))
	__timer_thread_dealloc (thread);
      else
	(void) __timer_thread_start (thread);

      pthread_mutex_unlock (&__timer_mutex);

      /* Unblock potentially blocked timer_delete().  */
      pthread_cond_broadcast (&thread->cond);
    }
}