librt/clock_getcpuclockid.c

   1 /* clock_getcpuclockid -- Get a clockid_t for process CPU time.  Linux version.
   2    Copyright (C) 2004, 2005 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <time.h>
  21 #include <sysdep.h>
  22 #include <unistd.h>
  23 #include <bits/kernel-features.h>
  24 #include "kernel-posix-cpu-timers.h"
  25
  26 #ifndef HAS_CPUCLOCK
  27 # define HAS_CPUCLOCK 1
  28 #endif
  29
  30 int
  31 clock_getcpuclockid (pid_t pid, clockid_t *clock_id)
  32 {
  33 #ifdef __NR_clock_getres
  34   /* The clockid_t value is a simple computation from the PID.
  35      But we do a clock_getres call to validate it.  */
  36
  37   const clockid_t pidclock = MAKE_PROCESS_CPUCLOCK (pid, CPUCLOCK_SCHED);
  38
  39 # if !(__ASSUME_POSIX_CPU_TIMERS > 0)
  40   extern int __libc_missing_posix_cpu_timers attribute_hidden;
  41 #  if !(__ASSUME_POSIX_TIMERS > 0)
  42   extern int __libc_missing_posix_timers attribute_hidden;
  43   if (__libc_missing_posix_timers && !__libc_missing_posix_cpu_timers)
  44     __libc_missing_posix_cpu_timers = 1;
  45 #  endif
  46   if (!__libc_missing_posix_cpu_timers)
  47 # endif
  48     {
  49       INTERNAL_SYSCALL_DECL (err);
  50       int r = INTERNAL_SYSCALL (clock_getres, err, 2, pidclock, NULL);
  51       if (!INTERNAL_SYSCALL_ERROR_P (r, err))
  52         {
  53           *clock_id = pidclock;
  54           return 0;
  55         }
  56
  57 # if !(__ASSUME_POSIX_TIMERS > 0)
  58       if (INTERNAL_SYSCALL_ERRNO (r, err) == ENOSYS)
  59         {
  60           /* The kernel doesn't support these calls at all.  */
  61           __libc_missing_posix_timers = 1;
  62           __libc_missing_posix_cpu_timers = 1;
  63         }
  64       else
  65 # endif
  66         if (INTERNAL_SYSCALL_ERRNO (r, err) == EINVAL)
  67           {
  68 # if !(__ASSUME_POSIX_CPU_TIMERS > 0)
  69             if (pidclock == MAKE_PROCESS_CPUCLOCK (0, CPUCLOCK_SCHED)
  70                 || INTERNAL_SYSCALL_ERROR_P (INTERNAL_SYSCALL
  71                                              (clock_getres, err, 2,
  72                                               MAKE_PROCESS_CPUCLOCK
  73                                               (0, CPUCLOCK_SCHED), NULL),
  74                                              err))
  75               /* The kernel doesn't support these clocks at all.  */
  76               __libc_missing_posix_cpu_timers = 1;
  77             else
  78 # endif
  79               /* The clock_getres system call checked the PID for us.  */
  80               return ESRCH;
  81           }
  82         else
  83           return INTERNAL_SYSCALL_ERRNO (r, err);
  84     }
  85 #endif
  86
  87   /* We don't allow any process ID but our own.  */
  88   if (pid != 0 && pid != getpid ())
  89     return EPERM;
  90
  91 #ifdef CLOCK_PROCESS_CPUTIME_ID
  92   if (HAS_CPUCLOCK)
  93     {
  94       /* Store the number.  */
  95       *clock_id = CLOCK_PROCESS_CPUTIME_ID;
  96
  97       return 0;
  98     }
  99 #endif
 100
 101   /* We don't have a timer for that.  */
 102   return ENOENT;
 103 }