glibc/linuxthreads/pthread.c

/* Linuxthreads - a simple clone()-based implementation of Posix        */
/* threads for Linux.                                                   */
/* Copyright (C) 1996 Xavier Leroy (Xavier.Leroy@inria.fr)              */
/*                                                                      */
/* 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"

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

extern 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.  */
extern int _errno;
extern int _h_errno;

/* 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 */
  &_errno,                    /* int *p_errnop */
  0,                          /* int p_errno */
  &_h_errno,                  /* 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_errno, /* int *p_errnop */
  0,                          /* int p_errno */
  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 __linuxthread_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
      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;
    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 (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;
  __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);
  __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()
{
  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;
}

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

/* Process-wide exit() request */

static void pthread_onexit_process(int retcode, void *arg)
{
  if (__builtin_expect (__pthread_manager_request, 0) >= 0) {
    struct pthread_request request;
    pthread_descr self = thread_self();

    request.req_thread = self;
    request.req_kind = REQ_PROCESS_EXIT;
    request.req_args.exit.code = retcode;
    __libc_write(__pthread_manager_request,
		 (char *) &request, sizeof(request));
    suspend(self);
    /* Main thread should accumulate times for thread manager and its
       children, so that timings for main thread account for all threads. */
    if (self == __pthread_main_thread)
      {
	waitpid(__pthread_manager_thread.p_pid, NULL, __WCLONE);
	free (__pthread_manager_thread_bos);
	__pthread_manager_thread_bos = __pthread_manager_thread_tos = NULL;
      }
  }
}

#ifndef HAVE_Z_NODELETE
static int __pthread_atexit_retcode;

static void pthread_atexit_process(void *arg, int retcode)
{
  pthread_onexit_process (retcode ?: __pthread_atexit_retcode, arg);
}

static void pthread_atexit_retcode(void *arg, int retcode)
{
  __pthread_atexit_retcode = retcode;
}
#endif

/* The handler for the RESTART signal just records the signal received
   in the thread descriptor, and optionally performs a siglongjmp
   (for pthread_cond_timedwait). */

static void pthread_handle_sigrestart(int sig)
{
  pthread_descr self = thread_self();
  THREAD_SETMEM(self, p_signal, sig);
  if (THREAD_GETMEM(self, p_signal_jmp) != NULL)
    siglongjmp(*THREAD_GETMEM(self, p_signal_jmp), 1);
}

/* The handler for the CANCEL signal checks for cancellation
   (in asynchronous mode), for process-wide exit and exec requests.
   For the thread manager thread, redirect the signal to
   __pthread_manager_sighandler. */

static void pthread_handle_sigcancel(int sig)
{
  pthread_descr self = thread_self();
  sigjmp_buf * jmpbuf;

  if (self == &__pthread_manager_thread)
    {
      __pthread_manager_sighandler(sig);
      return;
    }
  if (__builtin_expect (__pthread_exit_requested, 0)) {
    /* Main thread should accumulate times for thread manager and its
       children, so that timings for main thread account for all threads. */
    if (self == __pthread_main_thread)
      waitpid(__pthread_manager_thread.p_pid, NULL, __WCLONE);
    _exit(__pthread_exit_code);
  }
  if (__builtin_expect (THREAD_GETMEM(self, p_canceled), 0)
      && THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE) {
    if (THREAD_GETMEM(self, p_canceltype) == PTHREAD_CANCEL_ASYNCHRONOUS)
      __pthread_do_exit(PTHREAD_CANCELED, CURRENT_STACK_FRAME);
    jmpbuf = THREAD_GETMEM(self, p_cancel_jmp);
    if (jmpbuf != NULL) {
      THREAD_SETMEM(self, p_cancel_jmp, NULL);
      siglongjmp(*jmpbuf, 1);
    }
  }
}

/* Handler for the DEBUG signal.
   The debugging strategy is as follows:
   On reception of a REQ_DEBUG request (sent by new threads created to
   the thread manager under debugging mode), the thread manager throws
   __pthread_sig_debug to itself. The debugger (if active) intercepts
   this signal, takes into account new threads and continue execution
   of the thread manager by propagating the signal because it doesn't
   know what it is specifically done for. In the current implementation,
   the thread manager simply discards it. */

static void pthread_handle_sigdebug(int sig)
{
  /* Nothing */
}

/* Reset the state of the thread machinery after a fork().
   Close the pipe used for requests and set the main thread to the forked
   thread.
   Notice that we can't free the stack segments, as the forked thread
   may hold pointers into them. */

void __pthread_reset_main_thread()
{
  pthread_descr self = thread_self();
  struct rlimit limit;

  if (__pthread_manager_request != -1) {
    /* Free the thread manager stack */
    free(__pthread_manager_thread_bos);
    __pthread_manager_thread_bos = __pthread_manager_thread_tos = NULL;
    /* Close the two ends of the pipe */
    __libc_close(__pthread_manager_request);
    __libc_close(__pthread_manager_reader);
    __pthread_manager_request = __pthread_manager_reader = -1;
  }

  /* Update the pid of the main thread */
  THREAD_SETMEM(self, p_pid, __getpid());
  /* Make the forked thread the main thread */
  __pthread_main_thread = self;
  THREAD_SETMEM(self, p_nextlive, self);
  THREAD_SETMEM(self, p_prevlive, self);
  /* Now this thread modifies the global variables.  */
  THREAD_SETMEM(self, p_errnop, &_errno);
  THREAD_SETMEM(self, p_h_errnop, &_h_errno);
  THREAD_SETMEM(self, p_resp, &_res);

  if (getrlimit (RLIMIT_STACK, &limit) == 0
      && limit.rlim_cur != limit.rlim_max) {
    limit.rlim_cur = limit.rlim_max;
    setrlimit(RLIMIT_STACK, &limit);
  }
}

/* Process-wide exec() request */

void __pthread_kill_other_threads_np(void)
{
  struct sigaction sa;
  /* Terminate all other threads and thread manager */
  pthread_onexit_process(0, NULL);
  /* Make current thread the main thread in case the calling thread
     changes its mind, does not exec(), and creates new threads instead. */
  __pthread_reset_main_thread();

  /* Reset the signal handlers behaviour for the signals the
     implementation uses since this would be passed to the new
     process.  */
  sigemptyset(&sa.sa_mask);
  sa.sa_flags = 0;
  sa.sa_handler = SIG_DFL;
  __libc_sigaction(__pthread_sig_restart, &sa, NULL);
  __libc_sigaction(__pthread_sig_cancel, &sa, NULL);
  if (__pthread_sig_debug > 0)
    __libc_sigaction(__pthread_sig_debug, &sa, NULL);
}
weak_alias (__pthread_kill_other_threads_np, pthread_kill_other_threads_np)

/* Concurrency symbol level.  */
static int current_level;

int __pthread_setconcurrency(int level)
{
  /* We don't do anything unless we have found a useful interpretation.  */
  current_level = level;
  return 0;
}
weak_alias (__pthread_setconcurrency, pthread_setconcurrency)

int __pthread_getconcurrency(void)
{
  return current_level;
}
weak_alias (__pthread_getconcurrency, pthread_getconcurrency)

/* Primitives for controlling thread execution */

void __pthread_wait_for_restart_signal(pthread_descr self)
{
  sigset_t mask;

  sigprocmask(SIG_SETMASK, NULL, &mask); /* Get current signal mask */
  sigdelset(&mask, __pthread_sig_restart); /* Unblock the restart signal */
  THREAD_SETMEM(self, p_signal, 0);
  do {
    sigsuspend(&mask);                   /* Wait for signal */
  } while (THREAD_GETMEM(self, p_signal) !=__pthread_sig_restart);

  READ_MEMORY_BARRIER(); /* See comment in __pthread_restart_new */
}

#if !__ASSUME_REALTIME_SIGNALS
/* The _old variants are for 2.0 and early 2.1 kernels which don't have RT
   signals.
   On these kernels, we use SIGUSR1 and SIGUSR2 for restart and cancellation.
   Since the restart signal does not queue, we use an atomic counter to create
   queuing semantics. This is needed to resolve a rare race condition in
   pthread_cond_timedwait_relative. */

void __pthread_restart_old(pthread_descr th)
{
  if (atomic_increment(&th->p_resume_count) == -1)
    kill(th->p_pid, __pthread_sig_restart);
}

void __pthread_suspend_old(pthread_descr self)
{
  if (atomic_decrement(&self->p_resume_count) <= 0)
    __pthread_wait_for_restart_signal(self);
}

int
__pthread_timedsuspend_old(pthread_descr self, const struct timespec *abstime)
{
  sigset_t unblock, initial_mask;
  int was_signalled = 0;
  sigjmp_buf jmpbuf;

  if (atomic_decrement(&self->p_resume_count) == 0) {
    /* Set up a longjmp handler for the restart signal, unblock
       the signal and sleep. */

    if (sigsetjmp(jmpbuf, 1) == 0) {
      THREAD_SETMEM(self, p_signal_jmp, &jmpbuf);
      THREAD_SETMEM(self, p_signal, 0);
      /* Unblock the restart signal */
      sigemptyset(&unblock);
      sigaddset(&unblock, __pthread_sig_restart);
      sigprocmask(SIG_UNBLOCK, &unblock, &initial_mask);

      while (1) {
	struct timeval now;
	struct timespec reltime;

	/* Compute a time offset relative to now.  */
	__gettimeofday (&now, NULL);
	reltime.tv_nsec = abstime->tv_nsec - now.tv_usec * 1000;
	reltime.tv_sec = abstime->tv_sec - now.tv_sec;
	if (reltime.tv_nsec < 0) {
	  reltime.tv_nsec += 1000000000;
	  reltime.tv_sec -= 1;
	}

	/* Sleep for the required duration. If woken by a signal,
	   resume waiting as required by Single Unix Specification.  */
	if (reltime.tv_sec < 0 || __libc_nanosleep(&reltime, NULL) == 0)
	  break;
      }

      /* Block the restart signal again */
      sigprocmask(SIG_SETMASK, &initial_mask, NULL);
      was_signalled = 0;
    } else {
      was_signalled = 1;
    }
    THREAD_SETMEM(self, p_signal_jmp, NULL);
  }

  /* Now was_signalled is true if we exited the above code
     due to the delivery of a restart signal.  In that case,
     we know we have been dequeued and resumed and that the
     resume count is balanced.  Otherwise, there are some
     cases to consider. First, try to bump up the resume count
     back to zero. If it goes to 1, it means restart() was
     invoked on this thread. The signal must be consumed
     and the count bumped down and everything is cool. We
     can return a 1 to the caller.
     Otherwise, no restart was delivered yet, so a potential
     race exists; we return a 0 to the caller which must deal
     with this race in an appropriate way; for example by
     atomically removing the thread from consideration for a
     wakeup---if such a thing fails, it means a restart is
     being delivered. */

  if (!was_signalled) {
    if (atomic_increment(&self->p_resume_count) != -1) {
      __pthread_wait_for_restart_signal(self);
      atomic_decrement(&self->p_resume_count); /* should be zero now! */
      /* woke spontaneously and consumed restart signal */
      return 1;
    }
    /* woke spontaneously but did not consume restart---caller must resolve */
    return 0;
  }
  /* woken due to restart signal */
  return 1;
}
#endif /* __ASSUME_REALTIME_SIGNALS */

void __pthread_restart_new(pthread_descr th)
{
  /* The barrier is proabably not needed, in which case it still documents
     our assumptions. The intent is to commit previous writes to shared
     memory so the woken thread will have a consistent view.  Complementary
     read barriers are present to the suspend functions. */
  WRITE_MEMORY_BARRIER();
  kill(th->p_pid, __pthread_sig_restart);
}

/* There is no __pthread_suspend_new because it would just
   be a wasteful wrapper for __pthread_wait_for_restart_signal */

int
__pthread_timedsuspend_new(pthread_descr self, const struct timespec *abstime)
{
  sigset_t unblock, initial_mask;
  int was_signalled = 0;
  sigjmp_buf jmpbuf;

  if (sigsetjmp(jmpbuf, 1) == 0) {
    THREAD_SETMEM(self, p_signal_jmp, &jmpbuf);
    THREAD_SETMEM(self, p_signal, 0);
    /* Unblock the restart signal */
    sigemptyset(&unblock);
    sigaddset(&unblock, __pthread_sig_restart);
    sigprocmask(SIG_UNBLOCK, &unblock, &initial_mask);

    while (1) {
      struct timeval now;
      struct timespec reltime;

      /* Compute a time offset relative to now.  */
      __gettimeofday (&now, NULL);
      reltime.tv_nsec = abstime->tv_nsec - now.tv_usec * 1000;
      reltime.tv_sec = abstime->tv_sec - now.tv_sec;
      if (reltime.tv_nsec < 0) {
	reltime.tv_nsec += 1000000000;
	reltime.tv_sec -= 1;
      }

      /* Sleep for the required duration. If woken by a signal,
	 resume waiting as required by Single Unix Specification.  */
      if (reltime.tv_sec < 0 || __libc_nanosleep(&reltime, NULL) == 0)
	break;
    }

    /* Block the restart signal again */
    sigprocmask(SIG_SETMASK, &initial_mask, NULL);
    was_signalled = 0;
  } else {
    was_signalled = 1;
  }
  THREAD_SETMEM(self, p_signal_jmp, NULL);

  /* Now was_signalled is true if we exited the above code
     due to the delivery of a restart signal.  In that case,
     everything is cool. We have been removed from whatever
     we were waiting on by the other thread, and consumed its signal.

     Otherwise we this thread woke up spontaneously, or due to a signal other
     than restart. This is an ambiguous case  that must be resolved by
     the caller; the thread is still eligible for a restart wakeup
     so there is a race. */

  READ_MEMORY_BARRIER(); /* See comment in __pthread_restart_new */
  return was_signalled;
}


/* Debugging aid */

#ifdef DEBUG
#include <stdarg.h>

void __pthread_message(char * fmt, ...)
{
  char buffer[1024];
  va_list args;
  sprintf(buffer, "%05d : ", __getpid());
  va_start(args, fmt);
  vsnprintf(buffer + 8, sizeof(buffer) - 8, fmt, args);
  va_end(args);
  __libc_write(2, buffer, strlen(buffer));
}

#endif


#ifndef SHARED
/* We need a hook to force the cancelation wrappers to be linked in when
   static libpthread is used.  */
extern const int __pthread_provide_wrappers;
static const int *const __pthread_require_wrappers =
  &__pthread_provide_wrappers;
#endif