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This implements a full memory barrier. On ubuntu amd64 with results in an 'mfence' instruction. This is required to syncronization between threads, where there's typically only one write of a memory that should be synced between all threads with the barrier. Much more details can be found here: https://gcc.gnu.org/onlinedocs/gcc-7.3.0/gcc/_005f_005fatomic-Builtins.html#g_t_005f_005fatomic-Builtins https://gcc.gnu.org/onlinedocs/gcc-7.3.0/gcc/_005f_005fsync-Builtins.html#g_t_005f_005fsync-Builtins The main one we use seems to be in C11 via stdatomic.h, the oldest fallback is __sync_synchronize(), which is available since 2005 in gcc. Signed-off-by: Stefan Metzmacher <metze@samba.org> Reviewed-by: Ralph Boehme <slow@samba.org>
73 lines
2.4 KiB
C
73 lines
2.4 KiB
C
#ifndef _system_threads_h
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#define _system_threads_h
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/*
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Unix SMB/CIFS implementation.
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macros to go along with the lib/replace/ portability layer code
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Copyright (C) Volker Lendecke 2012
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** NOTE! The following LGPL license applies to the replace
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** library. This does NOT imply that all of Samba is released
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** under the LGPL
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 3 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, see <http://www.gnu.org/licenses/>.
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*/
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#include <pthread.h>
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#if defined(HAVE_PTHREAD_MUTEXATTR_SETROBUST_NP) && \
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!defined(HAVE_PTHREAD_MUTEXATTR_SETROBUST)
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#define pthread_mutexattr_setrobust pthread_mutexattr_setrobust_np
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#endif
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#if defined(HAVE_DECL_PTHREAD_MUTEX_ROBUST_NP) && \
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!defined(HAVE_DECL_PTHREAD_MUTEX_ROBUST)
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#define PTHREAD_MUTEX_ROBUST PTHREAD_MUTEX_ROBUST_NP
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#endif
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#if defined(HAVE_PTHREAD_MUTEX_CONSISTENT_NP) && \
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!defined(HAVE_PTHREAD_MUTEX_CONSISTENT)
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#define pthread_mutex_consistent pthread_mutex_consistent_np
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#endif
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#ifdef HAVE_STDATOMIC_H
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#include <stdatomic.h>
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#endif
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#ifndef HAVE_ATOMIC_THREAD_FENCE
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#ifdef HAVE___ATOMIC_THREAD_FENCE
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#define atomic_thread_fence(__ignore_order) __atomic_thread_fence(__ATOMIC_SEQ_CST)
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#define HAVE_ATOMIC_THREAD_FENCE 1
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#endif /* HAVE___ATOMIC_THREAD_FENCE */
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#endif /* not HAVE_ATOMIC_THREAD_FENCE */
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#ifndef HAVE_ATOMIC_THREAD_FENCE
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#ifdef HAVE___SYNC_SYNCHRONIZE
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#define atomic_thread_fence(__ignore_order) __sync_synchronize()
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#define HAVE_ATOMIC_THREAD_FENCE 1
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#endif /* HAVE___SYNC_SYNCHRONIZE */
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#endif /* not HAVE_ATOMIC_THREAD_FENCE */
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#ifndef HAVE_ATOMIC_THREAD_FENCE
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#ifdef HAVE_ATOMIC_THREAD_FENCE_SUPPORT
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#error mismatch_error_between_configure_test_and_header
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#endif
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/* make sure the build fails if someone uses it without checking the define */
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#define atomic_thread_fence(__order) \
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__function__atomic_thread_fence_not_available_on_this_platform__()
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#endif /* not HAVE_ATOMIC_THREAD_FENCE */
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#endif
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