:: RootR ::  Hosting Order Map Login   Secure Inter-Network Operations  
pthread_create(3) - phpMan

Command: man perldoc info search(apropos)  

PTHREAD_CREATE(3)                   Linux Programmer's Manual                   PTHREAD_CREATE(3)

       pthread_create - create a new thread

       #include <pthread.h>

       int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
                          void *(*start_routine) (void *), void *arg);

       Compile and link with -pthread.

       The  pthread_create() function starts a new thread in the calling process.  The new thread
       starts execution by invoking start_routine(); arg  is  passed  as  the  sole  argument  of

       The new thread terminates in one of the following ways:

       * It  calls  pthread_exit(3), specifying an exit status value that is available to another
         thread in the same process that calls pthread_join(3).

       * It returns from start_routine().  This is equivalent to calling pthread_exit(3) with the
         value supplied in the return statement.

       * It is canceled (see pthread_cancel(3)).

       * Any  of  the  threads in the process calls exit(3), or the main thread performs a return
         from main().  This causes the termination of all threads in the process.

       The attr argument points to a pthread_attr_t structure whose contents are used  at  thread
       creation  time  to  determine attributes for the new thread; this structure is initialized
       using pthread_attr_init(3) and related functions.  If attr is NULL,  then  the  thread  is
       created with default attributes.

       Before returning, a successful call to pthread_create() stores the ID of the new thread in
       the buffer pointed to by thread; this identifier is used to refer to the thread in  subse‐
       quent calls to other pthreads functions.

       The  new thread inherits a copy of the creating thread's signal mask (pthread_sigmask(3)).
       The set of pending signals for the new thread is empty (sigpending(2)).   The  new  thread
       does not inherit the creating thread's alternate signal stack (sigaltstack(2)).

       The new thread inherits the calling thread's floating-point environment (fenv(3)).

       The initial value of the new thread's CPU-time clock is 0 (see pthread_getcpuclockid(3)).

   Linux-specific details
       The  new  thread  inherits  copies  of the calling thread's capability sets (see capabili‐
       ties(7)) and CPU affinity mask (see sched_setaffinity(2)).

       On success, pthread_create() returns 0; on error, it returns an error number, and the con‐
       tents of *thread are undefined.

       EAGAIN Insufficient resources to create another thread.

       EAGAIN A  system-imposed limit on the number of threads was encountered.  There are a num‐
              ber of limits that may trigger this error: the  RLIMIT_NPROC  soft  resource  limit
              (set via setrlimit(2)), which limits the number of processes and threads for a real
              user ID, was reached; the kernel's system-wide limit on the number of processes and
              threads,  /proc/sys/kernel/threads-max,  was  reached (see proc(5)); or the maximum
              number of PIDs, /proc/sys/kernel/pid_max, was reached (see proc(5)).

       EINVAL Invalid settings in attr.

       EPERM  No permission to set the scheduling policy and parameters specified in attr.


       See pthread_self(3) for further information on  the  thread  ID  returned  in  *thread  by
       pthread_create().   Unless  real-time scheduling policies are being employed, after a call
       to pthread_create(), it is indeterminate which thread—the caller or  the  new  thread—will
       next execute.

       A thread may either be joinable or detached.  If a thread is joinable, then another thread
       can call pthread_join(3) to wait for the thread to terminate and fetch  its  exit  status.
       Only  when  a  terminated  joinable  thread  has been joined are the last of its resources
       released back to the system.  When a detached thread terminates, its resources  are  auto‐
       matically released back to the system: it is not possible to join with the thread in order
       to obtain its exit status.  Making a thread detached is useful for some  types  of  daemon
       threads  whose exit status the application does not need to care about.  By default, a new
       thread is created in a joinable state, unless attr was set  to  create  the  thread  in  a
       detached state (using pthread_attr_setdetachstate(3)).

       On  Linux/x86-32,  the default stack size for a new thread is 2 megabytes.  Under the NPTL
       threading implementation, if the RLIMIT_STACK soft resource limit at the time the  program
       started has any value other than "unlimited", then it determines the default stack size of
       new threads.  Using pthread_attr_setstacksize(3), the stack size attribute can be  explic‐
       itly  set  in  the  attr argument used to create a thread, in order to obtain a stack size
       other than the default.

       In the obsolete LinuxThreads implementation, each of the threads in a process has  a  dif‐
       ferent  process  ID.   This is in violation of the POSIX threads specification, and is the
       source of many other nonconformances to the standard; see pthreads(7).

       The program below demonstrates the use of pthread_create(), as well as a number  of  other
       functions in the pthreads API.

       In  the  following run, on a system providing the NPTL threading implementation, the stack
       size defaults to the value given by the "stack size" resource limit:

           $ ulimit -s
           8192            # The stack size limit is 8 MB (0x800000 bytes)
           $ ./a.out hola salut servus
           Thread 1: top of stack near 0xb7dd03b8; argv_string=hola
           Thread 2: top of stack near 0xb75cf3b8; argv_string=salut
           Thread 3: top of stack near 0xb6dce3b8; argv_string=servus
           Joined with thread 1; returned value was HOLA
           Joined with thread 2; returned value was SALUT
           Joined with thread 3; returned value was SERVUS

       In the next run, the program explicitly sets a stack size of 1MB (using  pthread_attr_set‐
       stacksize(3)) for the created threads:

           $ ./a.out -s 0x100000 hola salut servus
           Thread 1: top of stack near 0xb7d723b8; argv_string=hola
           Thread 2: top of stack near 0xb7c713b8; argv_string=salut
           Thread 3: top of stack near 0xb7b703b8; argv_string=servus
           Joined with thread 1; returned value was HOLA
           Joined with thread 2; returned value was SALUT
           Joined with thread 3; returned value was SERVUS

   Program source

       #include <pthread.h>
       #include <string.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <unistd.h>
       #include <errno.h>
       #include <ctype.h>

       #define handle_error_en(en, msg) \
               do { errno = en; perror(msg); exit(EXIT_FAILURE); } while (0)

       #define handle_error(msg) \
               do { perror(msg); exit(EXIT_FAILURE); } while (0)

       struct thread_info {    /* Used as argument to thread_start() */
           pthread_t thread_id;        /* ID returned by pthread_create() */
           int       thread_num;       /* Application-defined thread # */
           char     *argv_string;      /* From command-line argument */

       /* Thread start function: display address near top of our stack,
          and return upper-cased copy of argv_string */

       static void *
       thread_start(void *arg)
           struct thread_info *tinfo = arg;
           char *uargv, *p;

           printf("Thread %d: top of stack near %p; argv_string=%s\n",
                   tinfo->thread_num, &p, tinfo->argv_string);

           uargv = strdup(tinfo->argv_string);
           if (uargv == NULL)

           for (p = uargv; *p != '\0'; p++)
               *p = toupper(*p);

           return uargv;

       main(int argc, char *argv[])
           int s, tnum, opt, num_threads;
           struct thread_info *tinfo;
           pthread_attr_t attr;
           int stack_size;
           void *res;

           /* The "-s" option specifies a stack size for our threads */

           stack_size = -1;
           while ((opt = getopt(argc, argv, "s:")) != -1) {
               switch (opt) {
               case 's':
                   stack_size = strtoul(optarg, NULL, 0);

                   fprintf(stderr, "Usage: %s [-s stack-size] arg...\n",

           num_threads = argc - optind;

           /* Initialize thread creation attributes */

           s = pthread_attr_init(&attr);
           if (s != 0)
               handle_error_en(s, "pthread_attr_init");

           if (stack_size > 0) {
               s = pthread_attr_setstacksize(&attr, stack_size);
               if (s != 0)
                   handle_error_en(s, "pthread_attr_setstacksize");

           /* Allocate memory for pthread_create() arguments */

           tinfo = calloc(num_threads, sizeof(struct thread_info));
           if (tinfo == NULL)

           /* Create one thread for each command-line argument */

           for (tnum = 0; tnum < num_threads; tnum++) {
               tinfo[tnum].thread_num = tnum + 1;
               tinfo[tnum].argv_string = argv[optind + tnum];

               /* The pthread_create() call stores the thread ID into
                  corresponding element of tinfo[] */

               s = pthread_create(&tinfo[tnum].thread_id, &attr,
                                  &thread_start, &tinfo[tnum]);
               if (s != 0)
                   handle_error_en(s, "pthread_create");

           /* Destroy the thread attributes object, since it is no
              longer needed */

           s = pthread_attr_destroy(&attr);
           if (s != 0)
               handle_error_en(s, "pthread_attr_destroy");

           /* Now join with each thread, and display its returned value */

           for (tnum = 0; tnum < num_threads; tnum++) {
               s = pthread_join(tinfo[tnum].thread_id, &res);
               if (s != 0)
                   handle_error_en(s, "pthread_join");

               printf("Joined with thread %d; returned value was %s\n",
                       tinfo[tnum].thread_num, (char *) res);
               free(res);      /* Free memory allocated by thread */


       getrlimit(2), pthread_attr_init(3), pthread_cancel(3), pthread_detach(3),
       pthread_equal(3), pthread_exit(3), pthread_getattr_np(3), pthread_join(3),
       pthread_self(3), pthreads(7)

       This page is part of release 3.74 of the Linux man-pages project.  A description of the
       project, information about reporting bugs, and the latest version of this page, can be
       found at http://www.kernel.org/doc/man-pages/.

Linux                                       2014-05-28                          PTHREAD_CREATE(3)

rootr.net - man pages