1 .\" Copyright (c) 2009 Linux Foundation, written by Michael Kerrisk
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26 .TH PTHREAD_GETCPUCLOCKID 3 2017-09-15 "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 *" clock_id );
36 Compile and link with \fI\-pthread\fP.
40 .BR pthread_getcpuclockid ()
41 function returns the clock ID for the CPU time clock of the thread
43 .\" The clockid is constructed as follows:
44 .\" *clockid = CLOCK_THREAD_CPUTIME_ID | (pd->tid << CLOCK_IDFIELD_SIZE)
45 .\" where CLOCK_IDFIELD_SIZE is 3.
47 On success, this function returns 0;
48 on error, it returns a nonzero error number.
52 .\" CLOCK_THREAD_CPUTIME_ID not defined
53 Per-thread CPU time clocks are not supported by the system.
55 .\" Looking at nptl/pthread_getcpuclockid.c an ERANGE error would
56 .\" be possible if kernel thread IDs took more than 29 bits (which
57 .\" they currently cannot).
64 This function is available in glibc since version 2.2.
66 For an explanation of the terms used in this section, see
72 Interface Attribute Value
74 .BR pthread_getcpuclockid ()
75 T} Thread safety MT-Safe
78 POSIX.1-2001, POSIX.1-2008.
82 refers to the calling thread,
83 this function returns an identifier that refers to the same clock
88 when given the clock ID
89 .BR CLOCK_THREAD_CPUTIME_ID .
91 The program below creates a thread and then uses
93 to retrieve the total process CPU time,
94 and the per-thread CPU time consumed by the two threads.
95 The following shell session shows an example run:
101 Subthread starting infinite loop
102 Main thread consuming some CPU time...
103 Process total CPU time: 1.368
104 Main thread CPU time: 0.376
105 Subthread CPU time: 0.992
111 /* Link with "\-lrt" */
121 #define handle_error(msg) \\
122 do { perror(msg); exit(EXIT_FAILURE); } while (0)
124 #define handle_error_en(en, msg) \\
125 do { errno = en; perror(msg); exit(EXIT_FAILURE); } while (0)
128 thread_start(void *arg)
130 printf("Subthread starting infinite loop\\n");
136 pclock(char *msg, clockid_t cid)
141 if (clock_gettime(cid, &ts) == \-1)
142 handle_error("clock_gettime");
143 printf("%4ld.%03ld\\n", ts.tv_sec, ts.tv_nsec / 1000000);
147 main(int argc, char *argv[])
153 s = pthread_create(&thread, NULL, thread_start, NULL);
155 handle_error_en(s, "pthread_create");
157 printf("Main thread sleeping\\n");
160 printf("Main thread consuming some CPU time...\\n");
161 for (j = 0; j < 2000000; j++)
164 pclock("Process total CPU time: ", CLOCK_PROCESS_CPUTIME_ID);
166 s = pthread_getcpuclockid(pthread_self(), &cid);
168 handle_error_en(s, "pthread_getcpuclockid");
169 pclock("Main thread CPU time: ", cid);
171 /* The preceding 4 lines of code could have been replaced by:
172 pclock("Main thread CPU time: ", CLOCK_THREAD_CPUTIME_ID); */
174 s = pthread_getcpuclockid(thread, &cid);
176 handle_error_en(s, "pthread_getcpuclockid");
177 pclock("Subthread CPU time: 1 ", cid);
179 exit(EXIT_SUCCESS); /* Terminates both threads */
183 .BR clock_gettime (2),
184 .BR clock_settime (2),
185 .BR timer_create (2),
186 .BR clock_getcpuclockid (3),
187 .BR pthread_self (3),