diff options
author | Waldemar Brodkorb <wbx@openadk.org> | 2014-09-20 22:36:23 +0200 |
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committer | Waldemar Brodkorb <wbx@openadk.org> | 2014-09-22 20:35:40 +0200 |
commit | 4c3023bc803012656cf45749960282351efc8020 (patch) | |
tree | 979feef511fde3dbe564e5362e89a2e8b793909e /libpthread/nptl/sysdeps/unix/sysv/linux/xtensa/pthread_once.c | |
parent | 51f9b66d2fee1c7c1088b548751ac64131220b6e (diff) |
xtensa: add support for NPTL
Changes from:
https://github.com/foss-xtensa/uClibc/commits/xtensa_nptl
Author: Chris Zankel <chris@zankel.net>
Author: Baruch Siach <baruch@tkos.co.il>
Diffstat (limited to 'libpthread/nptl/sysdeps/unix/sysv/linux/xtensa/pthread_once.c')
-rw-r--r-- | libpthread/nptl/sysdeps/unix/sysv/linux/xtensa/pthread_once.c | 89 |
1 files changed, 89 insertions, 0 deletions
diff --git a/libpthread/nptl/sysdeps/unix/sysv/linux/xtensa/pthread_once.c b/libpthread/nptl/sysdeps/unix/sysv/linux/xtensa/pthread_once.c new file mode 100644 index 000000000..46085d3b5 --- /dev/null +++ b/libpthread/nptl/sysdeps/unix/sysv/linux/xtensa/pthread_once.c @@ -0,0 +1,89 @@ +/* Copyright (C) 2004-2013 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library. If not, see + <http://www.gnu.org/licenses/>. */ + +#include "pthreadP.h" +#include <lowlevellock.h> + +unsigned long int __fork_generation attribute_hidden; + +static void +clear_once_control (void *arg) +{ + pthread_once_t *once_control = (pthread_once_t *) arg; + + *once_control = 0; + lll_futex_wake (once_control, INT_MAX, LLL_PRIVATE); +} + +int +__pthread_once (pthread_once_t *once_control, void (*init_routine) (void)) +{ + for (;;) + { + int oldval; + int newval; + + /* Pseudo code: + newval = __fork_generation | 1; + oldval = *once_control; + if ((oldval & 2) == 0) + *once_control = newval; + Do this atomically. + */ + do + { + newval = __fork_generation | 1; + oldval = *once_control; + if (oldval & 2) + break; + } while (atomic_compare_and_exchange_val_acq (once_control, newval, oldval) != oldval); + + /* Check if the initializer has already been done. */ + if ((oldval & 2) != 0) + return 0; + + /* Check if another thread already runs the initializer. */ + if ((oldval & 1) == 0) + break; + + /* Check whether the initializer execution was interrupted by a fork. */ + if (oldval != newval) + break; + + /* Same generation, some other thread was faster. Wait. */ + lll_futex_wait (once_control, oldval, LLL_PRIVATE); + } + + /* This thread is the first here. Do the initialization. + Register a cleanup handler so that in case the thread gets + interrupted the initialization can be restarted. */ + pthread_cleanup_push (clear_once_control, once_control); + + init_routine (); + + pthread_cleanup_pop (0); + + /* Say that the initialisation is done. */ + *once_control = __fork_generation | 2; + + /* Wake up all other threads. */ + lll_futex_wake (once_control, INT_MAX, LLL_PRIVATE); + + return 0; +} +weak_alias (__pthread_once, pthread_once) +strong_alias (__pthread_once, __pthread_once_internal) |