/*
* 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
#ifndef AO_BUILD
# define AO_BUILD
#endif
#undef AO_REQUIRE_CAS
#include "atomic_ops.h" /* Without cas emulation! */
#ifdef __cplusplus
extern "C" {
#endif
AO_API void AO_pause(int); /* defined below */
#ifdef __cplusplus
} /* extern "C" */
#endif
#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
#ifdef __cplusplus
extern "C" {
#endif
AO_API AO_t AO_fetch_compare_and_swap_emulation(volatile AO_t *addr,
AO_t old_val, AO_t new_val);
AO_API 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_API void AO_store_full_emulation(volatile AO_t *addr, AO_t val);
/* Lock for pthreads-based implementation. */
#ifndef AO_NO_PTHREADS
AO_API pthread_mutex_t AO_pt_lock;
#endif
#ifdef __cplusplus
} /* extern "C" */
#endif
#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,
};
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_API 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;
}
AO_API 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;
}
AO_API 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);
}
AO_API 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
}
}
