1 .\" Copyright (c) 2009 Linux Foundation, written by Michael Kerrisk
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26 .TH PTHREAD_GETCPUCLOCKID 3 2019-03-06 "Linux" "Linux Programmer's Manual"
28 pthread_getcpuclockid \- retrieve ID of a thread's CPU time clock
31 .B #include <pthread.h>
34 .BI "int pthread_getcpuclockid(pthread_t " thread ", clockid_t *" clockid );
36 Compile and link with \fI\-pthread\fP.
40 .BR pthread_getcpuclockid ()
41 function obtains the ID of the CPU-time clock of the thread whose ID is
44 and returns it in the location pointed to by
46 .\" The clockid is constructed as follows:
47 .\" *clockid = CLOCK_THREAD_CPUTIME_ID | (pd->tid << CLOCK_IDFIELD_SIZE)
48 .\" where CLOCK_IDFIELD_SIZE is 3.
50 On success, this function returns 0;
51 on error, it returns a nonzero error number.
55 .\" CLOCK_THREAD_CPUTIME_ID not defined
56 Per-thread CPU time clocks are not supported by the system.
58 .\" Looking at nptl/pthread_getcpuclockid.c an ERANGE error would
59 .\" be possible if kernel thread IDs took more than 29 bits (which
60 .\" they currently cannot).
67 This function is available in glibc since version 2.2.
69 For an explanation of the terms used in this section, see
75 Interface Attribute Value
77 .BR pthread_getcpuclockid ()
78 T} Thread safety MT-Safe
81 POSIX.1-2001, POSIX.1-2008.
85 refers to the calling thread,
86 this function returns an identifier that refers to the same clock
91 when given the clock ID
92 .BR CLOCK_THREAD_CPUTIME_ID .
94 The program below creates a thread and then uses
96 to retrieve the total process CPU time,
97 and the per-thread CPU time consumed by the two threads.
98 The following shell session shows an example run:
104 Subthread starting infinite loop
105 Main thread consuming some CPU time...
106 Process total CPU time: 1.368
107 Main thread CPU time: 0.376
108 Subthread CPU time: 0.992
114 /* Link with "\-lrt" */
124 #define handle_error(msg) \e
125 do { perror(msg); exit(EXIT_FAILURE); } while (0)
127 #define handle_error_en(en, msg) \e
128 do { errno = en; perror(msg); exit(EXIT_FAILURE); } while (0)
131 thread_start(void *arg)
133 printf("Subthread starting infinite loop\en");
139 pclock(char *msg, clockid_t cid)
144 if (clock_gettime(cid, &ts) == \-1)
145 handle_error("clock_gettime");
146 printf("%4ld.%03ld\en", ts.tv_sec, ts.tv_nsec / 1000000);
150 main(int argc, char *argv[])
156 s = pthread_create(&thread, NULL, thread_start, NULL);
158 handle_error_en(s, "pthread_create");
160 printf("Main thread sleeping\en");
163 printf("Main thread consuming some CPU time...\en");
164 for (j = 0; j < 2000000; j++)
167 pclock("Process total CPU time: ", CLOCK_PROCESS_CPUTIME_ID);
169 s = pthread_getcpuclockid(pthread_self(), &cid);
171 handle_error_en(s, "pthread_getcpuclockid");
172 pclock("Main thread CPU time: ", cid);
174 /* The preceding 4 lines of code could have been replaced by:
175 pclock("Main thread CPU time: ", CLOCK_THREAD_CPUTIME_ID); */
177 s = pthread_getcpuclockid(thread, &cid);
179 handle_error_en(s, "pthread_getcpuclockid");
180 pclock("Subthread CPU time: 1 ", cid);
182 exit(EXIT_SUCCESS); /* Terminates both threads */
186 .BR clock_gettime (2),
187 .BR clock_settime (2),
188 .BR timer_create (2),
189 .BR clock_getcpuclockid (3),
190 .BR pthread_self (3),