/*
* Copyright (c) 2003-2011 Hewlett-Packard Development Company, L.P.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
/*
* Initialized data and out-of-line functions to support atomic_ops.h
* go here. Currently this is needed only for pthread-based atomics
* emulation, or for compare-and-swap emulation.
* Pthreads emulation isn't useful on a native Windows platform, and
* cas emulation is not needed. Thus we skip this on Windows.
*/
#if defined(HAVE_CONFIG_H)
# include
"config.h"
#endif
#if (
defined(__hexagon__) ||
defined(__native_client__)) \
&& !
defined(AO_USE_NO_SIGNALS) && !
defined(AO_USE_NANOSLEEP)
/* Hexagon QuRT does not have sigprocmask (but Hexagon does not need */
/* emulation, so it is OK not to bother about signals blocking). */
/* Since NaCl is not recognized by configure yet, we do it here. */
# define AO_USE_NO_SIGNALS
# define AO_USE_NANOSLEEP
#endif
#if defined(AO_USE_WIN32_PTHREADS) && !
defined(AO_USE_NO_SIGNALS)
# define AO_USE_NO_SIGNALS
#endif
#if (
defined(__CYGWIN__) ||
defined(__GLIBC__) ||
defined(__GNU__) \
||
defined(__linux__)) \
&& !
defined(AO_USE_NO_SIGNALS) && !
defined(_GNU_SOURCE)
# define _GNU_SOURCE
1
#endif
#undef AO_REQUIRE_CAS
#include "atomic_ops.h" /* Without cas emulation! */
#if !
defined(_MSC_VER) && !
defined(__MINGW32__) && !
defined(__BORLANDC__) \
||
defined(AO_USE_NO_SIGNALS)
#ifndef AO_NO_PTHREADS
# include <pthread.h>
#endif
#ifndef AO_USE_NO_SIGNALS
# include <signal.h>
#endif
#ifdef AO_USE_NANOSLEEP
/* This requires _POSIX_TIMERS feature. */
# include <sys/time.h>
# include <time.h>
#elif defined(AO_USE_WIN32_PTHREADS)
# include <windows.h>
/* for Sleep() */
#elif defined(_HPUX_SOURCE)
# include <sys/time.h>
#else
# include <sys/select.h>
#endif
#ifndef AO_HAVE_double_t
# include
"atomic_ops/sysdeps/standard_ao_double_t.h"
#endif
/* Lock for pthreads-based implementation. */
#ifndef AO_NO_PTHREADS
pthread_mutex_t AO_pt_lock = PTHREAD_MUTEX_INITIALIZER;
#endif
/*
* Out of line compare-and-swap emulation based on test and set.
*
* We use a small table of locks for different compare_and_swap locations.
* Before we update perform a compare-and-swap, we grab the corresponding
* lock. Different locations may hash to the same lock, but since we
* never acquire more than one lock at a time, this can't deadlock.
* We explicitly disable signals while we perform this operation.
*
* TODO: Probably also support emulation based on Lamport
* locks, since we may not have test_and_set either.
*/
#define AO_HASH_SIZE
16
#define AO_HASH(x) (((
unsigned long)(x) >>
12) & (AO_HASH_SIZE-
1))
static AO_TS_t AO_locks[AO_HASH_SIZE] = {
AO_TS_INITIALIZER, AO_TS_INITIALIZER, AO_TS_INITIALIZER, AO_TS_INITIALIZER,
AO_TS_INITIALIZER, AO_TS_INITIALIZER, AO_TS_INITIALIZER, AO_TS_INITIALIZER,
AO_TS_INITIALIZER, AO_TS_INITIALIZER, AO_TS_INITIALIZER, AO_TS_INITIALIZER,
AO_TS_INITIALIZER, AO_TS_INITIALIZER, AO_TS_INITIALIZER, AO_TS_INITIALIZER,
};
void AO_pause(
int);
/* defined below */
static void lock_ool(
volatile AO_TS_t *l)
{
int i =
0;
while (AO_test_and_set_acquire(l) == AO_TS_SET)
AO_pause(++i);
}
AO_INLINE
void lock(
volatile AO_TS_t *l)
{
if (AO_EXPECT_FALSE(AO_test_and_set_acquire(l) == AO_TS_SET))
lock_ool(l);
}
AO_INLINE
void unlock(
volatile AO_TS_t *l)
{
AO_CLEAR(l);
}
#ifndef AO_USE_NO_SIGNALS
static sigset_t all_sigs;
static volatile AO_t initialized =
0;
static volatile AO_TS_t init_lock = AO_TS_INITIALIZER;
AO_INLINE
void block_all_signals(sigset_t *old_sigs_ptr)
{
if (AO_EXPECT_FALSE(!AO_load_acquire(&initialized)))
{
lock(&init_lock);
if (!initialized)
sigfillset(&all_sigs);
unlock(&init_lock);
AO_store_release(&initialized,
1);
}
sigprocmask(SIG_BLOCK, &all_sigs, old_sigs_ptr);
/* Neither sigprocmask nor pthread_sigmask is 100% */
/* guaranteed to work here. Sigprocmask is not */
/* guaranteed be thread safe, and pthread_sigmask */
/* is not async-signal-safe. Under linuxthreads, */
/* sigprocmask may block some pthreads-internal */
/* signals. So long as we do that for short periods, */
/* we should be OK. */
}
#endif /* !AO_USE_NO_SIGNALS */
AO_t AO_fetch_compare_and_swap_emulation(
volatile AO_t *addr, AO_t old_val,
AO_t new_val)
{
AO_TS_t *my_lock = AO_locks + AO_HASH(addr);
AO_t fetched_val;
# ifndef AO_USE_NO_SIGNALS
sigset_t old_sigs;
block_all_signals(&old_sigs);
# endif
lock(my_lock);
fetched_val = *addr;
if (fetched_val == old_val)
*addr = new_val;
unlock(my_lock);
# ifndef AO_USE_NO_SIGNALS
sigprocmask(SIG_SETMASK, &old_sigs, NULL);
# endif
return fetched_val;
}
int AO_compare_double_and_swap_double_emulation(
volatile AO_double_t *addr,
AO_t old_val1, AO_t old_val2,
AO_t new_val1, AO_t new_val2)
{
AO_TS_t *my_lock = AO_locks + AO_HASH(addr);
int result;
# ifndef AO_USE_NO_SIGNALS
sigset_t old_sigs;
block_all_signals(&old_sigs);
# endif
lock(my_lock);
if (addr -> AO_val1 == old_val1 && addr -> AO_val2 == old_val2)
{
addr -> AO_val1 = new_val1;
addr -> AO_val2 = new_val2;
result =
1;
}
else
result =
0;
unlock(my_lock);
# ifndef AO_USE_NO_SIGNALS
sigprocmask(SIG_SETMASK, &old_sigs, NULL);
# endif
return result;
}
void AO_store_full_emulation(
volatile AO_t *addr, AO_t val)
{
AO_TS_t *my_lock = AO_locks + AO_HASH(addr);
lock(my_lock);
*addr = val;
unlock(my_lock);
}
#else /* Non-posix platform */
# include <windows.h>
# define AO_USE_WIN32_PTHREADS
/* define to use Sleep() */
extern int AO_non_posix_implementation_is_entirely_in_headers;
#endif
static AO_t spin_dummy =
1;
/* Spin for 2**n units. */
static void AO_spin(
int n)
{
AO_t j = AO_load(&spin_dummy);
int i =
2 << n;
while (i-- >
0)
j += (j -
1) <<
2;
/* Given 'spin_dummy' is initialized to 1, j is 1 after the loop. */
AO_store(&spin_dummy, j);
}
void AO_pause(
int n)
{
if (n <
12)
AO_spin(n);
else
{
# ifdef AO_USE_NANOSLEEP
struct timespec ts;
ts.tv_sec =
0;
ts.tv_nsec = n >
28 ?
100000L *
1000 :
1L << (n -
2);
nanosleep(&ts,
0);
# elif
defined(AO_USE_WIN32_PTHREADS)
Sleep(n >
28 ?
100 /* millis */
: n <
22 ?
1 : (DWORD)
1 << (n -
22));
# else
struct timeval tv;
/* Short async-signal-safe sleep. */
int usec = n >
28 ?
100000 :
1 << (n -
12);
/* Use an intermediate variable (of int type) to avoid */
/* "shift followed by widening conversion" warning. */
tv.tv_sec =
0;
tv.tv_usec = usec;
(
void)select(
0,
0,
0,
0, &tv);
# endif
}
}
