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    Command:

    pthread_getattr_np

    
    
    

    SYNOPSIS

           #define _GNU_SOURCE             /* See feature_test_macros(7) */
           #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  upward  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  imple-
           mentation 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 nonzero
           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.
    
    
               $ ulimit -s      # No stack limit ==> 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)
    
                   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;
               }
    
               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 */
    
                   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)
    
    
    

    Linux 2010-09-10 PTHREAD_GETATTR_NP(3)

    
    
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