pthread.c

用于嵌入式Linux系统的标准C的库函数

/* Linuxthreads - a simple clone()-based implementation of Posix        */
/* threads for Linux.                                                   */
/* Copyright (C) 1996 Xavier Leroy ([e-mail])              */
/*                                                                      */
/* This program is free software; you can redistribute it and/or        */
/* modify it under the terms of the GNU Library General Public License  */
/* as published by the Free Software Foundation; either version 2       */
/* of the License, or (at your option) any later version.               */
/*                                                                      */
/* This program 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 Library General Public License for more details.                 */

/* Thread creation, initialization, and basic low-level routines */

#include <errno.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/wait.h>
#include <sys/resource.h>
#include <sys/sysctl.h>
#include <shlib-compat.h>
#include "pthread.h"
#include "internals.h"
#include "spinlock.h"
#include "restart.h"
#include <machine/syscall.h>

/* for threading we use processes so we require a few EL/IX level 2 and 
   level 3 syscalls.  We only allow this file to see them to preserve
   the interface. */
#if defined(_ELIX_LEVEL) && _ELIX_LEVEL < 3
static _syscall1_base(int,pipe,int *,filedes)
#endif /* _ELIX_LEVEL < 3 */

#if defined(_ELIX_LEVEL) && _ELIX_LEVEL < 2
static _syscall2_base(int,setrlimit,int,resource,const struct rlimit *,rlp)
int on_exit (void (*fn)(int, void *), void *arg)
{
  register struct _atexit *p;
  void (*x)(void) = (void (*)(void))fn;

/* _REENT_SMALL on_exit() doesn't allow more than the required 32 entries.  */
#ifndef _REENT_SMALL
  if ((p = _REENT->_atexit) == NULL)
    _REENT->_atexit = p = &_REENT->_atexit0;
  if (p->_ind >= _ATEXIT_SIZE)
    {
      if ((p = (struct _atexit *) malloc (sizeof *p)) == NULL)
        return -1;
      p->_ind = 0;
      p->_fntypes = 0;
      p->_next = _REENT->_atexit;
      _REENT->_atexit = p;
    }
#else
  p = &_REENT->_atexit;
  if (p->_ind >= _ATEXIT_SIZE)
    return -1;
#endif
  p->_fntypes |= (1 << p->_ind);
  p->_fnargs[p->_ind] = arg;
  p->_fns[p->_ind++] = x;
  return 0;
}

#endif /* _ELIX_LEVEL < 2 */

/* We need the global/static resolver state here.  */
#include <resolv.h>
#undef _res

/* FIXME: for now, set up _res here */
struct __res_state _res;

/* Sanity check.  */
#if __ASSUME_REALTIME_SIGNALS && !defined __SIGRTMIN
# error "This must not happen; new kernel assumed but old headers"
#endif

/* These variables are used by the setup code.  */

/* Descriptor of the initial thread */

struct _pthread_descr_struct __pthread_initial_thread = {
  {
    {
      &__pthread_initial_thread /* pthread_descr self */
    }
  },
  &__pthread_initial_thread,  /* pthread_descr p_nextlive */
  &__pthread_initial_thread,  /* pthread_descr p_prevlive */
  NULL,                       /* pthread_descr p_nextwaiting */
  NULL,			      /* pthread_descr p_nextlock */
  PTHREAD_THREADS_MAX,        /* pthread_t p_tid */
  0,                          /* int p_pid */
  0,                          /* int p_priority */
  &__pthread_handles[0].h_lock, /* struct _pthread_fastlock * p_lock */
  0,                          /* int p_signal */
  NULL,                       /* sigjmp_buf * p_signal_buf */
  NULL,                       /* sigjmp_buf * p_cancel_buf */
  0,                          /* char p_terminated */
  0,                          /* char p_detached */
  0,                          /* char p_exited */
  NULL,                       /* void * p_retval */
  0,                          /* int p_retval */
  NULL,                       /* pthread_descr p_joining */
  NULL,                       /* struct _pthread_cleanup_buffer * p_cleanup */
  0,                          /* char p_cancelstate */
  0,                          /* char p_canceltype */
  0,                          /* char p_canceled */
  &__pthread_initial_thread.p_reent, /* struct _reent *p_reentp */
  _REENT_INIT(__pthread_initial_thread.p_reent),  /* struct _reent p_reent */
  NULL,                       /* int *p_h_errnop */
  0,                          /* int p_h_errno */
  NULL,                       /* char * p_in_sighandler */
  0,                          /* char p_sigwaiting */
  PTHREAD_START_ARGS_INITIALIZER(NULL),
                              /* struct pthread_start_args p_start_args */
  {NULL},                     /* void ** p_specific[PTHREAD_KEY_1STLEVEL_SIZE] */
  {NULL},                     /* void * p_libc_specific[_LIBC_TSD_KEY_N] */
  1,                          /* int p_userstack */
  NULL,                       /* void * p_guardaddr */
  0,                          /* size_t p_guardsize */
  0,                          /* Always index 0 */
  0,                          /* int p_report_events */
  {{{0, }}, 0, NULL},         /* td_eventbuf_t p_eventbuf */
  __ATOMIC_INITIALIZER,       /* struct pthread_atomic p_resume_count */
  0,                          /* char p_woken_by_cancel */
  0,                          /* char p_condvar_avail */
  0,                          /* char p_sem_avail */
  NULL,                       /* struct pthread_extricate_if *p_extricate */
  NULL,	                      /* pthread_readlock_info *p_readlock_list; */
  NULL,                       /* pthread_readlock_info *p_readlock_free; */
  0                           /* int p_untracked_readlock_count; */
};

/* Descriptor of the manager thread; none of this is used but the error
   variables, the p_pid and p_priority fields,
   and the address for identification.  */

struct _pthread_descr_struct __pthread_manager_thread = {
  {
    {
      &__pthread_manager_thread /* pthread_descr self */
    }
  },
  NULL,                       /* pthread_descr p_nextlive */
  NULL,                       /* pthread_descr p_prevlive */
  NULL,                       /* pthread_descr p_nextwaiting */
  NULL,			      /* pthread_descr p_nextlock */
  0,                          /* int p_tid */
  0,                          /* int p_pid */
  0,                          /* int p_priority */
  &__pthread_handles[1].h_lock, /* struct _pthread_fastlock * p_lock */
  0,                          /* int p_signal */
  NULL,                       /* sigjmp_buf * p_signal_buf */
  NULL,                       /* sigjmp_buf * p_cancel_buf */
  0,                          /* char p_terminated */
  0,                          /* char p_detached */
  0,                          /* char p_exited */
  NULL,                       /* void * p_retval */
  0,                          /* int p_retval */
  NULL,                       /* pthread_descr p_joining */
  NULL,                       /* struct _pthread_cleanup_buffer * p_cleanup */
  0,                          /* char p_cancelstate */
  0,                          /* char p_canceltype */
  0,                          /* char p_canceled */
  &__pthread_manager_thread.p_reent, /* struct _reent *p_reentp */
  _REENT_INIT(__pthread_manager_thread.p_reent), /* struct _reent p_reent */
  NULL,                       /* int *p_h_errnop */
  0,                          /* int p_h_errno */
  NULL,                       /* char * p_in_sighandler */
  0,                          /* char p_sigwaiting */
  PTHREAD_START_ARGS_INITIALIZER(__pthread_manager),
                              /* struct pthread_start_args p_start_args */
  {NULL},                     /* void ** p_specific[PTHREAD_KEY_1STLEVEL_SIZE] */
  {NULL},                     /* void * p_libc_specific[_LIBC_TSD_KEY_N] */
  0,                          /* int p_userstack */
  NULL,                       /* void * p_guardaddr */
  0,                          /* size_t p_guardsize */
  1,                          /* Always index 1 */
  0,                          /* int p_report_events */
  {{{0, }}, 0, NULL},         /* td_eventbuf_t p_eventbuf */
  __ATOMIC_INITIALIZER,       /* struct pthread_atomic p_resume_count */
  0,                          /* char p_woken_by_cancel */
  0,                          /* char p_condvar_avail */
  0,                          /* char p_sem_avail */
  NULL,                       /* struct pthread_extricate_if *p_extricate */
  NULL,	                      /* pthread_readlock_info *p_readlock_list; */
  NULL,                       /* pthread_readlock_info *p_readlock_free; */
  0                           /* int p_untracked_readlock_count; */
};

/* Pointer to the main thread (the father of the thread manager thread) */
/* Originally, this is the initial thread, but this changes after fork() */

pthread_descr __pthread_main_thread = &__pthread_initial_thread;

/* Limit between the stack of the initial thread (above) and the
   stacks of other threads (below). Aligned on a STACK_SIZE boundary. */

char *__pthread_initial_thread_bos;

/* File descriptor for sending requests to the thread manager. */
/* Initially -1, meaning that the thread manager is not running. */

int __pthread_manager_request = -1;

/* Other end of the pipe for sending requests to the thread manager. */

int __pthread_manager_reader;

/* Limits of the thread manager stack */

char *__pthread_manager_thread_bos;
char *__pthread_manager_thread_tos;

/* For process-wide exit() */

int __pthread_exit_requested;
int __pthread_exit_code;

/* Maximum stack size.  */
size_t __pthread_max_stacksize;

/* Nozero if the machine has more than one processor.  */
int __pthread_smp_kernel;


#if !__ASSUME_REALTIME_SIGNALS
/* Pointers that select new or old suspend/resume functions
   based on availability of rt signals. */

void (*__pthread_restart)(pthread_descr) = __pthread_restart_old;
void (*__pthread_suspend)(pthread_descr) = __pthread_suspend_old;
int (*__pthread_timedsuspend)(pthread_descr, const struct timespec *) = __pthread_timedsuspend_old;
#endif	/* __ASSUME_REALTIME_SIGNALS */

/* Communicate relevant LinuxThreads constants to gdb */

const int __pthread_threads_max = PTHREAD_THREADS_MAX;
const int __pthread_sizeof_handle = sizeof(struct pthread_handle_struct);
const int __pthread_offsetof_descr = offsetof(struct pthread_handle_struct,
                                              h_descr);
const int __pthread_offsetof_pid = offsetof(struct _pthread_descr_struct,
                                            p_pid);
const int __linuxthreads_pthread_sizeof_descr
  = sizeof(struct _pthread_descr_struct);

/* Forward declarations */

static void pthread_onexit_process(int retcode, void *arg);
#ifndef HAVE_Z_NODELETE
static void pthread_atexit_process(void *arg, int retcode);
static void pthread_atexit_retcode(void *arg, int retcode);
#endif
static void pthread_handle_sigcancel(int sig);
static void pthread_handle_sigrestart(int sig);
static void pthread_handle_sigdebug(int sig);

/* CPU clock handling.  */
#if HP_TIMING_AVAIL
extern hp_timing_t _dl_cpuclock_offset;
#endif

/* Signal numbers used for the communication.
   In these variables we keep track of the used variables.  If the
   platform does not support any real-time signals we will define the
   values to some unreasonable value which will signal failing of all
   the functions below.  */
#ifndef __SIGRTMIN
static int current_rtmin = -1;
static int current_rtmax = -1;
int __pthread_sig_restart = SIGUSR1;
int __pthread_sig_cancel = SIGUSR2;
int __pthread_sig_debug;
#else
static int current_rtmin;
static int current_rtmax;

#if __SIGRTMAX - __SIGRTMIN >= 3
int __pthread_sig_restart = __SIGRTMIN;
int __pthread_sig_cancel = __SIGRTMIN + 1;
int __pthread_sig_debug = __SIGRTMIN + 2;
#else
int __pthread_sig_restart = SIGUSR1;
int __pthread_sig_cancel = SIGUSR2;
int __pthread_sig_debug;
#endif

static int rtsigs_initialized;

#if !__ASSUME_REALTIME_SIGNALS
# include "testrtsig.h"
#endif

static void
init_rtsigs (void)
{
#if !__ASSUME_REALTIME_SIGNALS
  if (__builtin_expect (!kernel_has_rtsig (), 0))
    {
      current_rtmin = -1;
      current_rtmax = -1;
# if __SIGRTMAX - __SIGRTMIN >= 3
      __pthread_sig_restart = SIGUSR1;
      __pthread_sig_cancel = SIGUSR2;
      __pthread_sig_debug = 0;
# endif
    }
  else
#endif	/* __ASSUME_REALTIME_SIGNALS */
    {
#if __SIGRTMAX - __SIGRTMIN >= 3
      current_rtmin = __SIGRTMIN + 3;
# if !__ASSUME_REALTIME_SIGNALS
      __pthread_restart = __pthread_restart_new;
      __pthread_suspend = __pthread_wait_for_restart_signal;
      __pthread_timedsuspend = __pthread_timedsuspend_new;
# endif /* __ASSUME_REALTIME_SIGNALS */
#else
      current_rtmin = __SIGRTMIN;
#endif

      current_rtmax = __SIGRTMAX;
    }

  rtsigs_initialized = 1;
}
#endif

/* Return number of available real-time signal with highest priority.  */
int
__libc_current_sigrtmin (void)
{
#ifdef __SIGRTMIN
  if (__builtin_expect (!rtsigs_initialized, 0))
    init_rtsigs ();
#endif
  return current_rtmin;
}

/* Return number of available real-time signal with lowest priority.  */
int
__libc_current_sigrtmax (void)
{
#ifdef __SIGRTMIN
  if (__builtin_expect (!rtsigs_initialized, 0))
    init_rtsigs ();
#endif
  return current_rtmax;
}

/* Allocate real-time signal with highest/lowest available
   priority.  Please note that we don't use a lock since we assume
   this function to be called at program start.  */
int
__libc_allocate_rtsig (int high)
{
#ifndef __SIGRTMIN
  return -1;
#else
  if (__builtin_expect (!rtsigs_initialized, 0))
    init_rtsigs ();
  if (__builtin_expect (current_rtmin == -1, 0)
      || __builtin_expect (current_rtmin > current_rtmax, 0))
    /* We don't have anymore signal available.  */
    return -1;

  return high ? current_rtmin++ : current_rtmax--;
#endif
}

/* The function we use to get the kernel revision.  */
extern int __sysctl (int *name, int nlen, void *oldval, size_t *oldlenp,
		     void *newval, size_t newlen);

/* Test whether the machine has more than one processor.  This is not the
   best test but good enough.  More complicated tests would require `malloc'
   which is not available at that time.  */
static int
is_smp_system (void)
{
  static const int sysctl_args[] = { CTL_KERN, KERN_VERSION };
  char buf[512];
  size_t reslen = sizeof (buf);

  /* Try reading the number using `sysctl' first.  */
  if (__sysctl ((int *) sysctl_args,
		sizeof (sysctl_args) / sizeof (sysctl_args[0]),
		buf, &reslen, NULL, 0) < 0)
    {
      /* This was not successful.  Now try reading the /proc filesystem.  */
      int fd = __open ("/proc/sys/kernel/version", O_RDONLY);
      if (__builtin_expect (fd, 0) == -1
	  || (reslen = __read (fd, buf, sizeof (buf))) <= 0)
	/* This also didn't work.  We give up and say it's a UP machine.  */
	buf[0] = '\0';

      __close (fd);
    }

  return strstr (buf, "SMP") != NULL;
}


/* Initialize the pthread library.
   Initialization is split in two functions:
   - a constructor function that blocks the __pthread_sig_restart signal
     (must do this very early, since the program could capture the signal