1.\" 2.\" This file and its contents are supplied under the terms of the 3.\" Common Development and Distribution License ("CDDL"), version 1.0. 4.\" You may only use this file in accordance with the terms of version 5.\" 1.0 of the CDDL. 6.\" 7.\" A full copy of the text of the CDDL should have accompanied this 8.\" source. A copy of the CDDL is also available via the Internet at 9.\" http://www.illumos.org/license/CDDL. 10.\" 11.\" 12.\" Copyright 2016 Joyent, Inc. 13.\" 14.Dd December 2, 2023 15.Dt PTHREAD_ATTR_GET_NP 3C 16.Os 17.Sh NAME 18.Nm pthread_attr_get_np 19.Nd get pthread attributes of a running thread 20.Sh SYNOPSIS 21.In pthread.h 22.Ft int 23.Fo pthread_attr_get_np 24.Fa "pthread_t thread" 25.Fa "pthread_attr_t *attr" 26.Fc 27.Sh DESCRIPTION 28The 29.Fn pthread_attr_get_np 30function provides a way to get the attributes of the thread 31.Fa thread 32after it has been created. 33This function is most commonly used to obtain the actual location and size of a 34thread's stack. 35.Pp 36The attributes pointer, 37.Fa attr , 38will be filled in with the current attributes for the thread. 39The attributes should be allocated by a call to 40.Xr pthread_attr_init 3C 41prior to calling the 42.Fn pthread_attr_get_np 43function. 44When 45.Fa attr 46is done being used, it should be destroyed through a call to 47.Xr pthread_attr_destroy 3C . 48.Pp 49The attributes of the thread 50.Fa thread 51will be the same as those passed in at the time 52.Xr pthread_create 3C 53was called (or the default set if none were specified), except that the 54following values will be updated: 55.Bl -tag -width Sy 56.It Sy Thread Stack Size 57If no explicit stack size was specified, then 58.Fa attr 59will contain the actual size of the stack. 60.Pp 61If the size of the stack was specified, then it may have been changed to 62ensure that the required alignment of the platform is satisfied. 63.It Sy The Stack Address 64If no stack address was specified, then 65.Fa attr 66will contain the actual address of the stack that the system allocated 67for the thread. 68.It Sy Thread Detach State 69The detach state, whether or not the thread may be joined by a call to 70.Xr pthread_join 3C , 71may have changed since the process was created due to a call to 72.Xr pthread_detach 3C . 73.Fa attr 74will reflect the current setting of 75.Fa thread . 76.It Sy Thread Scheduling Parameter 77The scheduling parameter attribute will be updated with the current 78scheduling parameter of 79.Fa thread . 80This is the same information as available through 81.Xr pthread_getschedparam 3C 82and it is the preferred interface for obtaining that information. 83.It Sy Thread Scheduling Policy 84The scheduling policy attribute of 85.Fa attr 86will be updated with the current scheduling policy being applied to the 87thread. 88This may have changed, for example, due to a call to 89.Xr pthread_setschedparam 3C . 90As with the thread's scheduling parameter, the preferred interface for 91obtaining this information is by using 92.Xr pthread_getschedparam 3C . 93.It Sy Thread Guard Size 94The value of the guard size attribute for the thread will be updated to 95reflect the actual size of the guard installed for 96.Fa thread . 97For more information on the guard size of a thread and its purpose, see 98.Xr pthread_attr_getguardsize 3C . 99.El 100.Sh RETURN VALUES 101Upon successful completion, the 102.Fn pthread_attr_get_np 103function returns 104.Sy 0 . 105Otherwise, an error number is returned to indicate the error. 106.Sh EXAMPLES 107The following program demonstrates how to use this function to get 108the location and stack size of a newly created thread. 109.Bd -literal 110#include <assert.h> 111#include <errno.h> 112#include <pthread.h> 113#include <stdio.h> 114#include <stdlib.h> 115#include <string.h> 116 117static pthread_t g_thr; 118 119void * 120print_stackinfo(void *arg) 121{ 122 int ret; 123 pthread_attr_t attr; 124 pthread_t *thrp = arg; 125 void *stk; 126 size_t stksize; 127 128 if (pthread_attr_init(&attr) != 0) { 129 fprintf(stderr, "failed to init attr: %s\en", 130 strerror(errno)); 131 exit(1); 132 } 133 134 if (pthread_attr_get_np(*thrp, &attr) != 0) { 135 fprintf(stderr, "failed to get thread attributes: %s\en", 136 strerror(errno)); 137 exit(1); 138 } 139 140 ret = pthread_attr_getstackaddr(&attr, &stk); 141 assert(ret == 0); 142 ret = pthread_attr_getstacksize(&attr, &stksize); 143 assert(ret == 0); 144 (void) printf("stack base is at %p, it is %d bytes large\en", 145 stk, stksize); 146 return (NULL); 147} 148 149int 150main(void) 151{ 152 int ret; 153 154 if ((ret = pthread_create(&g_thr, NULL, print_stackinfo, 155 &g_thr) != 0)) { 156 fprintf(stderr, "failed to create a thread: %s\en", 157 strerror(errno)); 158 exit(1); 159 } 160 161 pthread_join(g_thr, NULL); 162 return (0); 163} 164.Ed 165.Sh ERRORS 166The 167.Fn pthread_attr_get_np 168function will fail if: 169.Bl -tag -width Er 170.It Er EINVAL 171The pthread_attr_t object 172.Fa attr 173was not properly initialized with a call to 174.Xr pthread_attr_init 3C . 175.It Er ESRCH 176No thread could be found corresponding to the specified thread ID, 177.Fa thread . 178.El 179.Sh INTERFACE STABILITY 180.Sy Committed 181.Sh MT-LEVEL 182.Sy MT-Safe 183.Sh SEE ALSO 184.Xr pthread_attr_destroy 3C , 185.Xr pthread_attr_getdetachstate 3C , 186.Xr pthread_attr_getguardsize 3C , 187.Xr pthread_attr_getinheritsched 3C , 188.Xr pthread_attr_getschedparam 3C , 189.Xr pthread_attr_getschedpolicy 3C , 190.Xr pthread_attr_getscope 3C , 191.Xr pthread_attr_getstackaddr 3C , 192.Xr pthread_attr_getstacksize 3C , 193.Xr pthread_attr_init 3C , 194.Xr pthread_create 3C , 195.Xr pthread_detach 3C , 196.Xr pthread_getschedparam 3C , 197.Xr pthread_setschedparam 3C , 198.Xr attributes 7 , 199.Xr threads 7 200