The OpenNET Project / Index page

[ новости /+++ | форум | теги | ]

Интерактивная система просмотра системных руководств (man-ов)

 ТемаНаборКатегория 
 
 [Cписок руководств | Печать]

pthread_getattr_np (3)
  • >> pthread_getattr_np (3) ( Linux man: Библиотечные вызовы )
  •  

    NAME

    pthread_getattr_np - get attributes of created thread
     
    

    SYNOPSIS

    #define _GNU_SOURCE
    #include <pthread.h>
    
    int pthread_getattr_np(pthread_t thread, pthread_attr_t *attr);
    
    Compile and link with -pthread.
    
     

    DESCRIPTION

    The pthread_getattr_np() function initializes the thread attributes object referred to by attr so that it contains actual attribute values describing the running thread thread.

    The returned attribute values may differ from the corresponding attribute values passed in the attr object that was used to create the thread using pthread_create(3). In particular, the following attributes may differ:

    *
    the detach state, since a joinable thread may have detached itself after creation;
    *
    the stack size, which the implementation may align to a suitable boundary.
    *
    and the guard size, which the implementation may round upwards to a multiple of the page size, or ignore (i.e., treat as 0), if the application is allocating its own stack.

    Furthermore, if the stack address attribute was not set in the thread attributes object used to create the thread, then the returned thread attributes object will report the actual stack address that the implementation selected for the thread.

    When the thread attributes object returned by pthread_getattr_np() is no longer required, it should be destroyed using pthread_attr_destroy(3).  

    RETURN VALUE

    On success, this function returns 0; on error, it returns a non-zero error number.  

    ERRORS

    ENOMEM
    Insufficient memory.

    In addition, if thread refers to the main thread, then pthread_getattr_np() can fail because of errors from various underlying calls: fopen(3), if /proc/self/maps can't be opened; and getrlimit(2), if the RLIMIT_STACK resource limit is not supported.  

    VERSIONS

    This function is available in glibc since version 2.2.3.  

    CONFORMING TO

    This function is a non-standard GNU extension. hence the suffix "_np" (non-portable) in the name.  

    EXAMPLE

    The program below demonstrates the use of pthread_getattr_np(). The program creates a thread that then uses pthread_getattr_np() to retrieve and display its guard size, stack address, and stack size attributes. Command-line arguments can be used to set these attributes to values other than the default when creating the thread. The shell sessions below demonstrate the use of the program.

    In the first run, on an x86-32 system, a thread is created using default attributes:

    $ ulimit -s      # No stack imit ==> default stack size is 2MB
    unlimited
    $ ./a.out
    Attributes of created thread:
            Guard size          = 4096 bytes
            Stack address       = 0x40196000 (EOS = 0x40397000)
            Stack size          = 0x201000 (2101248) bytes
    

    In the following run, we see that if a guard size is specified, it is rounded up to the next multiple of the system page size (4096 bytes on x86-32):

    $ ./a.out -g 4097
    Thread attributes object after initializations:
            Guard size          = 4097 bytes
            Stack address       = (nil)
            Stack size          = 0x0 (0) bytes
    
    Attributes of created thread:
            Guard size          = 8192 bytes
            Stack address       = 0x40196000 (EOS = 0x40397000)
            Stack size          = 0x201000 (2101248) bytes
    

    In the last run, the program manually allocates a stack for the thread. In this case, the guard size attribute is ignored.

    $ ./a.out -g 4096 -s 0x8000 -a
    Allocated thread stack at 0x804d000
    
    Thread attributes object after initializations:
            Guard size          = 4096 bytes
            Stack address       = 0x804d000 (EOS = 0x8055000)
            Stack size          = 0x8000 (32768) bytes
    
    Attributes of created thread:
            Guard size          = 0 bytes
            Stack address       = 0x804d000 (EOS = 0x8055000)
            Stack size          = 0x8000 (32768) bytes
    
     

    Program source

    #define _GNU_SOURCE     /* To get pthread_getattr_np() declaration */
    #include <pthread.h>
    #include <stdio.h>
    #include <stdlib.h>
    #include <unistd.h>
    #include <errno.h>
    
    #define handle_error_en(en, msg) \
            do { errno = en; perror(msg); exit(EXIT_FAILURE); } while (0)
    
    static void
    display_stack_related_attributes(pthread_attr_t *attr, char *prefix)
    {
        int s;
        size_t stack_size, guard_size;
        void *stack_addr;
    
        s = pthread_attr_getguardsize(attr, &guard_size);
        if (s != 0)
            handle_error_en(s, "pthread_attr_getguardsize");
        printf("%sGuard size          = %d bytes\n", prefix, guard_size);
    
        s = pthread_attr_getstack(attr, &stack_addr, &stack_size);
        if (s != 0)
            handle_error_en(s, "pthread_attr_getstack");
        printf("%sStack address       = %p", prefix, stack_addr);
        if (stack_size > 0)
            printf(" (EOS = %p)", (char *) stack_addr + stack_size);
        printf("\n");
        printf("%sStack size          = 0x%x (%d) bytes\n",
                prefix, stack_size, stack_size);
    }
    
    static void
    display_thread_attributes(pthread_t thread, char *prefix)
    {
        int s;
        pthread_attr_t attr;
    
        s = pthread_getattr_np(thread, &attr);
        if (s != 0)
            handle_error_en(s, "pthread_getattr_np");
    
        display_stack_related_attributes(&attr, prefix);
    
        s = pthread_attr_destroy(&attr);
        if (s != 0)
            handle_error_en(s, "pthread_attr_destroy");
    }
    
    static void *           /* Start function for thread we create */
    thread_start(void *arg)
    {
        printf("Attributes of created thread:\n");
        display_thread_attributes(pthread_self(), "\t");
    
        exit(EXIT_SUCCESS);         /* Terminate all threads */
    }
    
    static void
    usage(char *pname, char *msg)
    {
        if (msg != NULL)
            fputs(msg, stderr);
        fprintf(stderr, "Usage: %s [-s stack-size [-a]]"
                " [-g guard-size]\n", pname);
        fprintf(stderr, "\t\t-a means program should allocate stack\n");
        exit(EXIT_FAILURE);
    }
    
    static pthread_attr_t *   /* Get thread attributes from command line */
    get_thread_attributes_from_cl(int argc, char *argv[],
                                  pthread_attr_t *attrp)
    {
        int s, opt, allocate_stack;
        long stack_size, guard_size;
                void *stack_addr;
        pthread_attr_t *ret_attrp = NULL;   /* Set to attrp if we initialize
                                               a thread attributes object */
        allocate_stack = 0;
        stack_size = -1;
        guard_size = -1;
    
        while ((opt = getopt(argc, argv, "ag:s:")) != -1) {
            switch (opt) {
            case aqaaq:   allocate_stack = 1;                     break;
            case aqgaq:   guard_size = strtoul(optarg, NULL, 0);  break;
            case aqsaq:   stack_size = strtoul(optarg, NULL, 0);  break;
            default:    usage(argv[0], NULL);
            }
        }
    
        if (allocate_stack && stack_size == -1)
            usage(argv[0], "Specifying -a without -s makes no sense\n");
    
        if (argc > optind)
            usage(argv[0], "Extraneous command-line arguments\n");
    
        if (stack_size >= 0 || guard_size > 0) {
            ret_attrp = attrp;
    
            s = pthread_attr_init(attrp);
            if (s != 0)
                handle_error_en(s, "pthread_attr_init");
        }
    
        if (stack_size >= 0) {
            if (!allocate_stack) {
                s = pthread_attr_setstacksize(attrp, stack_size);
                if (s != 0)
                    handle_error_en(s, "pthread_attr_setstacksize");
            } else {
                s = posix_memalign(&stack_addr, sysconf(_SC_PAGESIZE),
                                   stack_size);
                if (s != 0)
                    handle_error_en(s, "posix_memalign");
                printf("Allocated thread stack at %p\n\n", stack_addr);
    
                s = pthread_attr_setstack(attrp, stack_addr, stack_size);
                if (s != 0)
                    handle_error_en(s, "pthread_attr_setstacksize");
            }
        }
    
        if (guard_size >= 0) {
            s = pthread_attr_setguardsize(attrp, guard_size);
            if (s != 0)
                handle_error_en(s, "pthread_attr_setstacksize");
        }
    
        return ret_attrp;
    }
    
    int
    main(int argc, char *argv[])
    {
        int s;
        pthread_t thr;
        pthread_attr_t attr;
        pthread_attr_t *attrp = NULL;    /* Set to &attr if we initialize
                                            a thread attributes object */
    
        attrp = get_thread_attributes_from_cl(argc, argv, &attr);
    
        if (attrp != NULL) {
            printf("Thread attributes object after initializations:\n");
            display_stack_related_attributes(attrp, "\t");
            printf("\n");
        }
    
        s = pthread_create(&thr, attrp, &thread_start, NULL);
        if (s != 0)
            handle_error_en(s, "pthread_create");
    
        if (attrp != NULL) {
            s = pthread_attr_destroy(attrp);
            if (s != 0)
                handle_error_en(s, "pthread_attr_destroy");
        }
    
        pause();    /* Terminates when other thread calls exit() */
    }
    
     

    SEE ALSO

    pthread_attr_getaffinity_np(3), pthread_attr_getdetachstate(3), pthread_attr_getguardsize(3), pthread_attr_getinheritsched(3), pthread_attr_getschedparam(3), pthread_attr_getschedpolicy(3), pthread_attr_getscope(3), pthread_attr_getstack(3), pthread_attr_getstackaddr(3), pthread_attr_getstacksize(3), pthread_attr_init(3), pthread_create(3), pthreads(7)  

    COLOPHON

    This page is part of release 3.14 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.


     

    Index

    NAME
    SYNOPSIS
    DESCRIPTION
    RETURN VALUE
    ERRORS
    VERSIONS
    CONFORMING TO
    EXAMPLE
    Program source
    SEE ALSO
    COLOPHON


    Поиск по тексту MAN-ов: 




    Партнёры:
    PostgresPro
    Inferno Solutions
    Hosting by Hoster.ru
    Хостинг:

    Закладки на сайте
    Проследить за страницей
    Created 1996-2024 by Maxim Chirkov
    Добавить, Поддержать, Вебмастеру