117 lines
2.9 KiB
C
117 lines
2.9 KiB
C
/* Copyright (C) 2012 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 Atomic Library (libatomic).
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Libatomic is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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Libatomic 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 General Public License for
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more details.
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Under Section 7 of GPL version 3, you are granted additional
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permissions described in the GCC Runtime Library Exception, version
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3.1, as published by the Free Software Foundation.
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You should have received a copy of the GNU General Public License and
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a copy of the GCC Runtime Library Exception along with this program;
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see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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<http://www.gnu.org/licenses/>. */
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#include "libatomic_i.h"
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#include <pthread.h>
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/* The target page size. Must be no larger than the runtime page size,
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lest locking fail with virtual address aliasing (i.e. a page mmaped
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at two locations). */
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#ifndef PAGE_SIZE
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#define PAGE_SIZE 4096
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#endif
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/* The target cacheline size. This is an optimization; the padding that
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should be applied to the locks to keep them from interfering. */
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#ifndef CACHLINE_SIZE
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#define CACHLINE_SIZE 64
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#endif
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/* The granularity at which locks are applied. Almost certainly the
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cachline size is the right thing to use here. */
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#ifndef WATCH_SIZE
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#define WATCH_SIZE CACHLINE_SIZE
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#endif
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struct lock
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{
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pthread_mutex_t mutex;
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char pad[sizeof(pthread_mutex_t) < CACHLINE_SIZE
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? CACHLINE_SIZE - sizeof(pthread_mutex_t)
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: 0];
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};
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#define NLOCKS (PAGE_SIZE / WATCH_SIZE)
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static struct lock locks[NLOCKS] = {
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[0 ... NLOCKS-1].mutex = PTHREAD_MUTEX_INITIALIZER
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};
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static inline uintptr_t
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addr_hash (void *ptr)
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{
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return ((uintptr_t)ptr / WATCH_SIZE) % NLOCKS;
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}
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void
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libat_lock_1 (void *ptr)
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{
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pthread_mutex_lock (&locks[addr_hash (ptr)].mutex);
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}
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void
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libat_unlock_1 (void *ptr)
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{
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pthread_mutex_unlock (&locks[addr_hash (ptr)].mutex);
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}
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void
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libat_lock_n (void *ptr, size_t n)
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{
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uintptr_t h = addr_hash (ptr);
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size_t i = 0;
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/* Don't lock more than all the locks we have. */
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if (n > PAGE_SIZE)
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n = PAGE_SIZE;
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do
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{
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pthread_mutex_lock (&locks[h].mutex);
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if (++h == NLOCKS)
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h = 0;
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i += WATCH_SIZE;
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}
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while (i < n);
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}
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void
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libat_unlock_n (void *ptr, size_t n)
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{
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uintptr_t h = addr_hash (ptr);
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size_t i = 0;
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if (n > PAGE_SIZE)
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n = PAGE_SIZE;
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do
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{
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pthread_mutex_unlock (&locks[h].mutex);
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if (++h == NLOCKS)
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h = 0;
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i += WATCH_SIZE;
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}
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while (i < n);
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}
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