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glibc  2.9
sem_post.c
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00001 /* sem_post -- post to a POSIX semaphore.  Powerpc version.
00002    Copyright (C) 2003, 2004, 2007 Free Software Foundation, Inc.
00003    This file is part of the GNU C Library.
00004    Contributed by Paul Mackerras <paulus@au.ibm.com>, 2003.
00005 
00006    The GNU C Library is free software; you can redistribute it and/or
00007    modify it under the terms of the GNU Lesser General Public
00008    License as published by the Free Software Foundation; either
00009    version 2.1 of the License, or (at your option) any later version.
00010 
00011    The GNU C Library is distributed in the hope that it will be useful,
00012    but WITHOUT ANY WARRANTY; without even the implied warranty of
00013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00014    Lesser General Public License for more details.
00015 
00016    You should have received a copy of the GNU Lesser General Public
00017    License along with the GNU C Library; if not, write to the Free
00018    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00019    02111-1307 USA.  */
00020 
00021 #include <errno.h>
00022 #include <sysdep.h>
00023 #include <lowlevellock.h>
00024 #include <internaltypes.h>
00025 #include <semaphore.h>
00026 
00027 #include <shlib-compat.h>
00028 
00029 int
00030 __new_sem_post (sem_t *sem)
00031 {
00032   struct new_sem *isem = (struct new_sem *) sem;
00033 
00034   __asm __volatile (__lll_rel_instr ::: "memory");
00035   atomic_increment (&isem->value);
00036   __asm __volatile (__lll_acq_instr ::: "memory");
00037   if (isem->nwaiters > 0)
00038     {
00039       int err = lll_futex_wake (&isem->value, 1,
00040                             isem->private ^ FUTEX_PRIVATE_FLAG);
00041       if (__builtin_expect (err, 0) < 0)
00042        {
00043          __set_errno (-err);
00044          return -1;
00045        }
00046     }
00047   return 0;
00048 }
00049 versioned_symbol (libpthread, __new_sem_post, sem_post, GLIBC_2_1);
00050 
00051 #if SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_1)
00052 
00053 int
00054 attribute_compat_text_section
00055 __old_sem_post (sem_t *sem)
00056 {
00057   int *futex = (int *) sem;
00058 
00059   __asm __volatile (__lll_rel_instr ::: "memory");
00060   int nr = atomic_increment_val (futex);
00061   /* We always have to assume it is a shared semaphore.  */
00062   int err = lll_futex_wake (futex, 1, LLL_SHARED);
00063   if (__builtin_expect (err, 0) < 0)
00064     {
00065       __set_errno (-err);
00066       return -1;
00067     }
00068   return 0;
00069 }
00070 
00071 compat_symbol (libpthread, __old_sem_post, sem_post, GLIBC_2_0);
00072 #endif