183 lines
4.3 KiB
C
183 lines
4.3 KiB
C
/* Copyright (C) 2005 Free Software Foundation, Inc.
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Contributed by Richard Henderson <rth@redhat.com>.
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This file is part of the GNU OpenMP Library (libgomp).
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Libgomp is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for
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more details.
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You should have received a copy of the GNU Lesser General Public License
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along with libgomp; see the file COPYING.LIB. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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MA 02110-1301, USA. */
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/* As a special exception, if you link this library with other files, some
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of which are compiled with GCC, to produce an executable, this library
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does not by itself cause the resulting executable to be covered by the
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GNU General Public License. This exception does not however invalidate
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any other reasons why the executable file might be covered by the GNU
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General Public License. */
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/* This is a Linux specific implementation of the public OpenMP locking
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primitives. This implementation uses atomic instructions and the futex
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syscall. */
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#include "libgomp.h"
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#include <string.h>
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#include <unistd.h>
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#include <sys/syscall.h>
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#include "futex.h"
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/* The internal gomp_mutex_t and the external non-recursive omp_lock_t
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have the same form. Re-use it. */
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void
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omp_init_lock (omp_lock_t *lock)
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{
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gomp_mutex_init (lock);
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}
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void
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omp_destroy_lock (omp_lock_t *lock)
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{
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gomp_mutex_destroy (lock);
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}
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void
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omp_set_lock (omp_lock_t *lock)
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{
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gomp_mutex_lock (lock);
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}
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void
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omp_unset_lock (omp_lock_t *lock)
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{
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gomp_mutex_unlock (lock);
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}
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int
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omp_test_lock (omp_lock_t *lock)
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{
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return __sync_bool_compare_and_swap (lock, 0, 1);
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}
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/* The external recursive omp_nest_lock_t form requires additional work. */
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/* We need an integer to uniquely identify this thread. Most generally
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this is the thread's TID, which ideally we'd get this straight from
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the TLS block where glibc keeps it. Unfortunately, we can't get at
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that directly.
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If we don't support (or have disabled) TLS, one function call is as
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good (or bad) as any other. Use the syscall all the time.
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On an ILP32 system (defined here as not LP64), we can make do with
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any thread-local pointer. Ideally we'd use the TLS base address,
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since that requires the least amount of arithmetic, but that's not
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always available directly. Make do with the gomp_thread pointer
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since it's handy. */
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#if !defined (HAVE_TLS)
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static inline int gomp_tid (void)
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{
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return syscall (SYS_gettid);
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}
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#elif !defined(__LP64__)
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static inline int gomp_tid (void)
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{
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return (int) gomp_thread ();
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}
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#else
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static __thread int tid_cache;
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static inline int gomp_tid (void)
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{
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int tid = tid_cache;
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if (__builtin_expect (tid == 0, 0))
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tid_cache = tid = syscall (SYS_gettid);
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return tid;
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}
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#endif
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void
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omp_init_nest_lock (omp_nest_lock_t *lock)
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{
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memset (lock, 0, sizeof (lock));
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}
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void
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omp_destroy_nest_lock (omp_nest_lock_t *lock)
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{
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}
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void
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omp_set_nest_lock (omp_nest_lock_t *lock)
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{
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int otid, tid = gomp_tid ();
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while (1)
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{
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otid = __sync_val_compare_and_swap (&lock->owner, 0, tid);
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if (otid == 0)
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{
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lock->count = 1;
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return;
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}
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if (otid == tid)
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{
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lock->count++;
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return;
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}
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futex_wait (&lock->owner, otid);
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}
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}
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void
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omp_unset_nest_lock (omp_nest_lock_t *lock)
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{
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/* ??? Validate that we own the lock here. */
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if (--lock->count == 0)
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{
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__sync_lock_release (&lock->owner);
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futex_wake (&lock->owner, 1);
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}
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}
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int
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omp_test_nest_lock (omp_nest_lock_t *lock)
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{
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int otid, tid = gomp_tid ();
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otid = __sync_val_compare_and_swap (&lock->owner, 0, tid);
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if (otid == 0)
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{
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lock->count = 1;
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return 1;
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}
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if (otid == tid)
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return ++lock->count;
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return 0;
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}
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ialias (omp_init_lock)
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ialias (omp_init_nest_lock)
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ialias (omp_destroy_lock)
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ialias (omp_destroy_nest_lock)
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ialias (omp_set_lock)
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ialias (omp_set_nest_lock)
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ialias (omp_unset_lock)
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ialias (omp_unset_nest_lock)
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ialias (omp_test_lock)
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ialias (omp_test_nest_lock)
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