Bug 23304

While there is no problem with CLOCK_REALTIME, POSIX clock_gettime, clock_getres return errno invalid argument for CLOCK_PROF and CLOCK_VIRTUAL, which are documented in the man pages (section 2) as being user+system and user time, respectively.

Fix: 

Immediate fix: remove mention of CLOCK_VIRTUAL AND CLOCK_PROF from sys/time.h and man 2 clock_gettime

Real fix: implement the documented POSIX functionality
How-To-Repeat: /* demonstrates that the clock_get... calls succed for CLOCK_REALTIME but fail for CLOCK_PROF and CLOCK_VIRTUAL */
#include <sys/time.h>
#include <stdio.h>

int main() {
  struct timespec t;

  puts("CLOCK_PROF");
  if (clock_gettime(CLOCK_PROF, &t))
    perror(NULL);
  if (clock_getres(CLOCK_PROF, &t))
    perror(NULL);

  puts("\nCLOCK_VIRTUAL");
  if (clock_gettime(CLOCK_VIRTUAL, &t))
    perror(NULL);
  if (clock_getres(CLOCK_VIRTUAL, &t))
    perror(NULL);

  puts("\nCLOCK_REALTIME");
  if (clock_gettime(CLOCK_REALTIME, &t))
    perror(NULL);
  if (clock_getres(CLOCK_REALTIME, &t))
    perror(NULL);
}