nptl/sysdeps/unix/sysv/linux/pthread_getcpuclockid.c

   1 /* pthread_getcpuclockid -- Get POSIX clockid_t for a pthread_t.  Linux version
   2    Copyright (C) 2000-2012 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 License as
   7    published by the Free Software Foundation; either version 2.1 of the
   8    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; see the file COPYING.LIB.  If
  17    not, see <http://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <pthreadP.h>
  21 #include <sys/time.h>
  22 #include <tls.h>
  23 #include <kernel-features.h>
  24 #include <kernel-posix-cpu-timers.h>
  25
  26
  27 #if !(__ASSUME_POSIX_CPU_TIMERS > 0)
  28 int __libc_missing_posix_cpu_timers attribute_hidden;
  29 #endif
  30
  31 int
  32 pthread_getcpuclockid (threadid, clockid)
  33      pthread_t threadid;
  34      clockid_t *clockid;
  35 {
  36   struct pthread *pd = (struct pthread *) threadid;
  37
  38   /* Make sure the descriptor is valid.  */
  39   if (INVALID_TD_P (pd))
  40     /* Not a valid thread handle.  */
  41     return ESRCH;
  42
  43 #ifdef __NR_clock_getres
  44   /* The clockid_t value is a simple computation from the TID.
  45      But we do a clock_getres call to validate it if we aren't
  46      yet sure we have the kernel support.  */
  47
  48   const clockid_t tidclock = MAKE_THREAD_CPUCLOCK (pd->tid, CPUCLOCK_SCHED);
  49
  50 # if !(__ASSUME_POSIX_CPU_TIMERS > 0)
  51   if (!__libc_missing_posix_cpu_timers)
  52     {
  53       INTERNAL_SYSCALL_DECL (err);
  54       int r = INTERNAL_SYSCALL (clock_getres, err, 2, tidclock, NULL);
  55       if (!INTERNAL_SYSCALL_ERROR_P (r, err))
  56 # endif
  57         {
  58           *clockid = tidclock;
  59           return 0;
  60         }
  61
  62 # if !(__ASSUME_POSIX_CPU_TIMERS > 0)
  63       if (INTERNAL_SYSCALL_ERRNO (r, err) == EINVAL)
  64         {
  65           /* The kernel doesn't support these clocks at all.  */
  66           __libc_missing_posix_cpu_timers = 1;
  67         }
  68       else
  69         return INTERNAL_SYSCALL_ERRNO (r, err);
  70     }
  71 # endif
  72 #endif
  73
  74 #ifdef CLOCK_THREAD_CPUTIME_ID
  75   /* We need to store the thread ID in the CLOCKID variable together
  76      with a number identifying the clock.  We reserve the low 3 bits
  77      for the clock ID and the rest for the thread ID.  This is
  78      problematic if the thread ID is too large.  But 29 bits should be
  79      fine.
  80
  81      If some day more clock IDs are needed the ID part can be
  82      enlarged.  The IDs are entirely internal.  */
  83   if (pd->tid >= 1 << (8 * sizeof (*clockid) - CLOCK_IDFIELD_SIZE))
  84     return ERANGE;
  85
  86   /* Store the number.  */
  87   *clockid = CLOCK_THREAD_CPUTIME_ID | (pd->tid << CLOCK_IDFIELD_SIZE);
  88
  89   return 0;
  90 #else
  91   /* We don't have a timer for that.  */
  92   return ENOENT;
  93 #endif
  94 }