| /* Copyright (C) 2012-2022 Free Software Foundation, Inc. |
| Contributed by Richard Henderson <rth@redhat.com>. |
| |
| This file is part of the GNU Atomic Library (libatomic). |
| |
| Libatomic is free software; you can redistribute it and/or modify it |
| under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 3 of the License, or |
| (at your option) any later version. |
| |
| Libatomic 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 General Public License for |
| more details. |
| |
| Under Section 7 of GPL version 3, you are granted additional |
| permissions described in the GCC Runtime Library Exception, version |
| 3.1, as published by the Free Software Foundation. |
| |
| You should have received a copy of the GNU General Public License and |
| a copy of the GCC Runtime Library Exception along with this program; |
| see the files COPYING3 and COPYING.RUNTIME respectively. If not, see |
| <http://www.gnu.org/licenses/>. */ |
| |
| #include "libatomic_i.h" |
| #include <pthread.h> |
| |
| |
| /* The target page size. Must be no larger than the runtime page size, |
| lest locking fail with virtual address aliasing (i.e. a page mmaped |
| at two locations). */ |
| #ifndef PAGE_SIZE |
| #define PAGE_SIZE 4096 |
| #endif |
| |
| /* The target cacheline size. This is an optimization; the padding that |
| should be applied to the locks to keep them from interfering. */ |
| #ifndef CACHLINE_SIZE |
| #define CACHLINE_SIZE 64 |
| #endif |
| |
| /* The granularity at which locks are applied. Almost certainly the |
| cachline size is the right thing to use here. */ |
| #ifndef WATCH_SIZE |
| #define WATCH_SIZE CACHLINE_SIZE |
| #endif |
| |
| struct lock |
| { |
| pthread_mutex_t mutex; |
| char pad[sizeof(pthread_mutex_t) < CACHLINE_SIZE |
| ? CACHLINE_SIZE - sizeof(pthread_mutex_t) |
| : 0]; |
| }; |
| |
| #define NLOCKS (PAGE_SIZE / WATCH_SIZE) |
| static struct lock locks[NLOCKS] = { |
| [0 ... NLOCKS-1].mutex = PTHREAD_MUTEX_INITIALIZER |
| }; |
| |
| static inline uintptr_t |
| addr_hash (void *ptr) |
| { |
| return ((uintptr_t)ptr / WATCH_SIZE) % NLOCKS; |
| } |
| |
| void |
| libat_lock_1 (void *ptr) |
| { |
| pthread_mutex_lock (&locks[addr_hash (ptr)].mutex); |
| } |
| |
| void |
| libat_unlock_1 (void *ptr) |
| { |
| pthread_mutex_unlock (&locks[addr_hash (ptr)].mutex); |
| } |
| |
| void |
| libat_lock_n (void *ptr, size_t n) |
| { |
| uintptr_t h = addr_hash (ptr); |
| size_t i = 0; |
| |
| /* Don't lock more than all the locks we have. */ |
| if (n > PAGE_SIZE) |
| n = PAGE_SIZE; |
| |
| do |
| { |
| pthread_mutex_lock (&locks[h].mutex); |
| if (++h == NLOCKS) |
| h = 0; |
| i += WATCH_SIZE; |
| } |
| while (i < n); |
| } |
| |
| void |
| libat_unlock_n (void *ptr, size_t n) |
| { |
| uintptr_t h = addr_hash (ptr); |
| size_t i = 0; |
| |
| if (n > PAGE_SIZE) |
| n = PAGE_SIZE; |
| |
| do |
| { |
| pthread_mutex_unlock (&locks[h].mutex); |
| if (++h == NLOCKS) |
| h = 0; |
| i += WATCH_SIZE; |
| } |
| while (i < n); |
| } |