nptl/pthread_rwlock_unlock.c

   1 /* Copyright (C) 2003-2023 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 #include <errno.h>
  19 #include <sysdep.h>
  20 #include <futex-internal.h>
  21 #include <pthread.h>
  22 #include <pthreadP.h>
  23 #include <stap-probe.h>
  24
  25 #include "pthread_rwlock_common.c"
  26
  27 /* See pthread_rwlock_common.c for an overview.  */
  28 int
  29 ___pthread_rwlock_unlock (pthread_rwlock_t *rwlock)
  30 {
  31   LIBC_PROBE (rwlock_unlock, 1, rwlock);
  32
  33   /* We distinguish between having acquired a read vs. a write lock by looking
  34      at the writer TID.  If it's equal to our TID, we must be the writer
  35      because nobody else can have stored this value.  Also, if we are a
  36      reader, we will read from the wrunlock store with value 0 by the most
  37      recent writer because that writer happens-before us.  */
  38   if (atomic_load_relaxed (&rwlock->__data.__cur_writer)
  39       == THREAD_GETMEM (THREAD_SELF, tid))
  40       __pthread_rwlock_wrunlock (rwlock);
  41   else
  42     __pthread_rwlock_rdunlock (rwlock);
  43   return 0;
  44 }
  45 versioned_symbol (libc, ___pthread_rwlock_unlock, pthread_rwlock_unlock,
  46                   GLIBC_2_34);
  47 strong_alias (___pthread_rwlock_unlock, __pthread_rwlock_unlock)
  48 libc_hidden_ver (___pthread_rwlock_unlock, __pthread_rwlock_unlock)
  49
  50 #if OTHER_SHLIB_COMPAT (libpthread, GLIBC_2_1, GLIBC_2_34)
  51 compat_symbol (libpthread, ___pthread_rwlock_unlock, pthread_rwlock_unlock,
  52                GLIBC_2_1);
  53 #endif
  54 #if OTHER_SHLIB_COMPAT (libpthread, GLIBC_2_2, GLIBC_2_34)
  55 compat_symbol (libpthread, ___pthread_rwlock_unlock, __pthread_rwlock_unlock,
  56                GLIBC_2_2);
  57 #endif