pthread library source code reading

#include "pthread.h"
#include "implement.h"


int
pthread_attr_init (pthread_attr_t * attr)
     /*
      * ------------------------------------------------------
      * DOCPUBLIC
      *      Initializes a thread attributes object with default
      *      attributes.
      *
      * PARAMETERS
      *      attr
      *              pointer to an instance of pthread_attr_t
      *
      *
      * DESCRIPTION
      *      Initializes a thread attributes object with default
      *      attributes.
      *
      *      NOTES:
      *              1)      Used to define thread attributes
      *
      * RESULTS
      *              0               successfully initialized attr,
      *              ENOMEM          insufficient memory for attr.
      *
      * ------------------------------------------------------
      */
{
  pthread_attr_t attr_result;

  if (attr == NULL)
    {
      /* This is disallowed. */
      return EINVAL;
    }

  attr_result = (pthread_attr_t) malloc (sizeof (*attr_result));

  if (attr_result == NULL)
    {
      return ENOMEM;
    }

#ifdef _POSIX_THREAD_ATTR_STACKSIZE
  /*
   * Default to zero size. Unless changed explicitly this
   * will allow Win32 to set the size to that of the
   * main thread.
   */
  attr_result->stacksize = 0;
#endif

#ifdef _POSIX_THREAD_ATTR_STACKADDR
  /* FIXME: Set this to something sensible when we support it. */
  attr_result->stackaddr = NULL;
#endif

  // 设置线程默认是怎么退出的
  attr_result->detachstate = PTHREAD_CREATE_JOINABLE;

#if HAVE_SIGSET_T
  memset (&(attr_result->sigmask), 0, sizeof (sigset_t));
#endif /* HAVE_SIGSET_T */

  /*
   * Win32 sets new threads to THREAD_PRIORITY_NORMAL and
   * not to that of the parent thread. We choose to default to
   * this arrangement.
   */
  attr_result->param.sched_priority = THREAD_PRIORITY_NORMAL;
  attr_result->inheritsched = PTHREAD_EXPLICIT_SCHED;
  attr_result->contentionscope = PTHREAD_SCOPE_SYSTEM;

  attr_result->valid = PTW32_ATTR_VALID;

  *attr = attr_result;

  return 0;
}

#include "pthread.h"
#include "implement.h"
#ifndef _UWIN
#include <process.h>
#endif

int
pthread_create (pthread_t * tid,
        const pthread_attr_t * attr,
        void *(*start) (void *), void *arg)
     /*
      * ------------------------------------------------------
      * DOCPUBLIC
      *      This function creates a thread running the start function,
      *      passing it the parameter value, 'arg'. The 'attr'
      *      argument specifies optional creation attributes.
      *      The identity of the new thread is returned
      *      via 'tid', which should not be NULL.
      *
      * PARAMETERS
      *      tid
      *              pointer to an instance of pthread_t
      *
      *      attr
      *              optional pointer to an instance of pthread_attr_t
      *
      *      start
      *              pointer to the starting routine for the new thread
      *
      *      arg
      *              optional parameter passed to 'start'
      *
      *
      * DESCRIPTION
      *      This function creates a thread running the start function,
      *      passing it the parameter value, 'arg'. The 'attr'
      *      argument specifies optional creation attributes.
      *      The identity of the new thread is returned
      *      via 'tid', which should not be the NULL pointer.
      *
      * RESULTS
      *              0               successfully created thread,
      *              EINVAL          attr invalid,
      *              EAGAIN          insufficient resources.
      *
      * ------------------------------------------------------
      */
{
  pthread_t thread;
  ptw32_thread_t * tp;
  register pthread_attr_t a;
  HANDLE threadH = 0;
  int result = EAGAIN;
  int run = PTW32_TRUE;
  ThreadParms *parms = NULL;
  long stackSize;
  int priority;
  pthread_t self;

  /*
   * Before doing anything, check that tid can be stored through
   * without invoking a memory protection error (segfault).
   * Make sure that the assignment below can't be optimised out by the compiler.
   * This is assured by conditionally assigning *tid again at the end.
   */
  tid->x = 0;

  if (attr != NULL)
    {
      a = *attr;
    }
  else
    {
      a = NULL;
    }

  if ((thread = ptw32_new ()).p == NULL)
    {
      goto FAIL0;
    }

  tp = (ptw32_thread_t *) thread.p;

  priority = tp->sched_priority;

  if ((parms = (ThreadParms *) malloc (sizeof (*parms))) == NULL)
    {
      goto FAIL0;
    }

  parms->tid = thread;
  parms->start = start;
  parms->arg = arg;

#if defined(HAVE_SIGSET_T)

  /*
   * Threads inherit their initial sigmask from their creator thread.
   */
  self = pthread_self();
  tp->sigmask = ((ptw32_thread_t *)self.p)->sigmask;

#endif /* HAVE_SIGSET_T */


  if (a != NULL)
    {
      stackSize = a->stacksize;
      tp->detachState = a->detachstate;
      priority = a->param.sched_priority;

#if (THREAD_PRIORITY_LOWEST > THREAD_PRIORITY_NORMAL)
      /* WinCE */
#else
      /* Everything else */

      /*
       * Thread priority must be set to a valid system level
       * without altering the value set by pthread_attr_setschedparam().
       */

      /*
       * PTHREAD_EXPLICIT_SCHED is the default because Win32 threads
       * don't inherit their creator's priority. They are started with
       * THREAD_PRIORITY_NORMAL (win32 value). The result of not supplying
       * an 'attr' arg to pthread_create() is equivalent to defaulting to
       * PTHREAD_EXPLICIT_SCHED and priority THREAD_PRIORITY_NORMAL.
       */
      if (PTHREAD_INHERIT_SCHED == a->inheritsched)
    {
      /*
       * If the thread that called pthread_create() is a Win32 thread
       * then the inherited priority could be the result of a temporary
       * system adjustment. This is not the case for POSIX threads.
       */
#if ! defined(HAVE_SIGSET_T)
      self = pthread_self ();
#endif
      priority = ((ptw32_thread_t *) self.p)->sched_priority;
    }

#endif

    }
  else
    {
      /*
       * Default stackSize
       */
      stackSize = PTHREAD_STACK_MIN;
    }

  tp->state = run ? PThreadStateInitial : PThreadStateSuspended;

  tp->keys = NULL;

  /*
   * Threads must be started in suspended mode and resumed if necessary
   * after _beginthreadex returns us the handle. Otherwise we set up a
   * race condition between the creating and the created threads.
   * Note that we also retain a local copy of the handle for use
   * by us in case thread.p->threadH gets NULLed later but before we've
   * finished with it here.
   */

#if ! defined (__MINGW32__) || defined (__MSVCRT__) || defined (__DMC__) 

  tp->threadH =
    threadH =
    (HANDLE) _beginthreadex ((void *) NULL,    /* No security info             */
                 (unsigned) stackSize,    /* default stack size   */
                 ptw32_threadStart,
                 parms,
                 (unsigned)
                 CREATE_SUSPENDED,
                 (unsigned *) &(tp->thread));

  if (threadH != 0)
    {
      if (a != NULL)
    {
      (void) ptw32_setthreadpriority (thread, SCHED_OTHER, priority);
    }

      if (run)
    {
      ResumeThread (threadH);
    }
    }

#else /* __MINGW32__ && ! __MSVCRT__ */

  /*
   * This lock will force pthread_threadStart() to wait until we have
   * the thread handle and have set the priority.
   */
  (void) pthread_mutex_lock (&tp->cancelLock);

  tp->threadH =
    threadH =           // 线程创建最终调用了这个函数
    (HANDLE) _beginthread (ptw32_threadStart, (unsigned) stackSize,    /* default stack size   */
               parms);

  /*
   * Make the return code match _beginthreadex's.
   */
  if (threadH == (HANDLE) - 1L)
    {
      tp->threadH = threadH = 0;
    }
  else
    {
      if (!run)
    {
      /* 
       * beginthread does not allow for create flags, so we do it now.
       * Note that beginthread itself creates the thread in SUSPENDED
       * mode, and then calls ResumeThread to start it.
       */
      SuspendThread (threadH);
    }

      if (a != NULL)
    {
      (void) ptw32_setthreadpriority (thread, SCHED_OTHER, priority);
    }
    }

  (void) pthread_mutex_unlock (&tp->cancelLock);

#endif /* __MINGW32__ && ! __MSVCRT__ */

  result = (threadH != 0) ? 0 : EAGAIN;

  /*
   * Fall Through Intentionally
   */

  /*
   * ------------
   * Failure Code
   * ------------
   */

FAIL0:
  if (result != 0)
    {

      ptw32_threadDestroy (thread);
      tp = NULL;

      if (parms != NULL)
    {
      free (parms);
    }
    }
  else
    {
      *tid = thread;
    }

#ifdef _UWIN
  if (result == 0)
    pthread_count++;
#endif
  return (result);

}