1/* Copyright (C) 2012-2015 Free Software Foundation, Inc. 2 Contributed by Richard Henderson <rth@redhat.com>. 3 4 This file is part of the GNU Atomic Library (libatomic). 5 6 Libatomic is free software; you can redistribute it and/or modify it 7 under the terms of the GNU General Public License as published by 8 the Free Software Foundation; either version 3 of the License, or 9 (at your option) any later version. 10 11 Libatomic is distributed in the hope that it will be useful, but WITHOUT ANY 12 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS 13 FOR A PARTICULAR PURPOSE. See the GNU General Public License for 14 more details. 15 16 Under Section 7 of GPL version 3, you are granted additional 17 permissions described in the GCC Runtime Library Exception, version 18 3.1, as published by the Free Software Foundation. 19 20 You should have received a copy of the GNU General Public License and 21 a copy of the GCC Runtime Library Exception along with this program; 22 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 23 <http://www.gnu.org/licenses/>. */ 24 25#include "libatomic_i.h" 26#include <pthread.h> 27 28 29/* The target page size. Must be no larger than the runtime page size, 30 lest locking fail with virtual address aliasing (i.e. a page mmaped 31 at two locations). */ 32#ifndef PAGE_SIZE 33#define PAGE_SIZE 4096 34#endif 35 36/* The target cacheline size. This is an optimization; the padding that 37 should be applied to the locks to keep them from interfering. */ 38#ifndef CACHLINE_SIZE 39#define CACHLINE_SIZE 64 40#endif 41 42/* The granularity at which locks are applied. Almost certainly the 43 cachline size is the right thing to use here. */ 44#ifndef WATCH_SIZE 45#define WATCH_SIZE CACHLINE_SIZE 46#endif 47 48struct lock 49{ 50 pthread_mutex_t mutex; 51 char pad[sizeof(pthread_mutex_t) < CACHLINE_SIZE 52 ? CACHLINE_SIZE - sizeof(pthread_mutex_t) 53 : 0]; 54}; 55 56#define NLOCKS (PAGE_SIZE / WATCH_SIZE) 57static struct lock locks[NLOCKS] = { 58 [0 ... NLOCKS-1].mutex = PTHREAD_MUTEX_INITIALIZER 59}; 60 61static inline uintptr_t 62addr_hash (void *ptr) 63{ 64 return ((uintptr_t)ptr / WATCH_SIZE) % NLOCKS; 65} 66 67void 68libat_lock_1 (void *ptr) 69{ 70 pthread_mutex_lock (&locks[addr_hash (ptr)].mutex); 71} 72 73void 74libat_unlock_1 (void *ptr) 75{ 76 pthread_mutex_unlock (&locks[addr_hash (ptr)].mutex); 77} 78 79void 80libat_lock_n (void *ptr, size_t n) 81{ 82 uintptr_t h = addr_hash (ptr); 83 size_t i = 0; 84 85 /* Don't lock more than all the locks we have. */ 86 if (n > PAGE_SIZE) 87 n = PAGE_SIZE; 88 89 do 90 { 91 pthread_mutex_lock (&locks[h].mutex); 92 if (++h == NLOCKS) 93 h = 0; 94 i += WATCH_SIZE; 95 } 96 while (i < n); 97} 98 99void 100libat_unlock_n (void *ptr, size_t n) 101{ 102 uintptr_t h = addr_hash (ptr); 103 size_t i = 0; 104 105 if (n > PAGE_SIZE) 106 n = PAGE_SIZE; 107 108 do 109 { 110 pthread_mutex_unlock (&locks[h].mutex); 111 if (++h == NLOCKS) 112 h = 0; 113 i += WATCH_SIZE; 114 } 115 while (i < n); 116} 117