117 lines
2.9 KiB
C
117 lines
2.9 KiB
C
/* Copyright (C) 2012-2019 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);
|
|
}
|