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vpx/vp8/common/threading.h
Jim Bankoski 318a1ff5ec vp8 : use threading mutex's for tsan only. 
To avoid decode performance hit of 2% when running on hyperthreaded
cores.

This patch only uses the mutex's when we are running tsan.

This is safe because 32 bit operations like read and store are atomic
on all the platforms we care about. Tsan warns about race situations,
but in this case either situation ( read occurs before write or write
before read) the worst case is that we go around one extra time in the
loop.  So the ordering doesn't really matter.

That said a few other things have been tried :

for instance as per here:
webrtc/base/atomicops.h#52

In this patch they use:
__atomic_load_n(i, __ATOMIC_ACQUIRE);
__atomic_store_n(i, value, __ATOMIC_RELEASE);

This code works on gcc, clang ( replacing protected write and read), and
avoids tsan errors. Incurring no penalty in performance.  In C11 its
replaced by straight atomic operands.

However there is no equivalent in the visual studio's we support as
int32 on all windows platforms is already atomic.  To avoid tsan like
warnings on windows we'd need to use interlocked exchange and the
end result doesn't gain us any thing.

Change-Id: I2066e3c7f42641ebb23d53feb1f16f23f85bcf59
2016-12-16 08:50:55 -08:00

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/*
* Copyright (c) 2010 The WebM project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#ifndef VP8_COMMON_THREADING_H_
#define VP8_COMMON_THREADING_H_
#include "./vpx_config.h"
#ifdef __cplusplus
extern "C" {
#endif
#if CONFIG_OS_SUPPORT && CONFIG_MULTITHREAD
/* Thread management macros */
#if defined(_WIN32) && !HAVE_PTHREAD_H
/* Win32 */
#include <process.h>
#include <windows.h>
#if defined(__GNUC__) && \
(__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 2))
#define THREAD_FUNCTION \
__attribute__((force_align_arg_pointer)) unsigned int __stdcall
#else
#define THREAD_FUNCTION unsigned int __stdcall
#endif
#define THREAD_FUNCTION_RETURN DWORD
#define THREAD_SPECIFIC_INDEX DWORD
#define pthread_t HANDLE
#define pthread_attr_t DWORD
#define pthread_detach(thread) \
if (thread != NULL) CloseHandle(thread)
#define thread_sleep(nms) Sleep(nms)
#define pthread_cancel(thread) terminate_thread(thread, 0)
#define ts_key_create(ts_key, destructor) \
{ ts_key = TlsAlloc(); };
#define pthread_getspecific(ts_key) TlsGetValue(ts_key)
#define pthread_setspecific(ts_key, value) TlsSetValue(ts_key, (void *)value)
#define pthread_self() GetCurrentThreadId()
#elif defined(__OS2__)
/* OS/2 */
#define INCL_DOS
#include <os2.h>
#include <stdlib.h>
#define THREAD_FUNCTION void *
#define THREAD_FUNCTION_RETURN void *
#define THREAD_SPECIFIC_INDEX PULONG
#define pthread_t TID
#define pthread_attr_t ULONG
#define pthread_detach(thread) 0
#define thread_sleep(nms) DosSleep(nms)
#define pthread_cancel(thread) DosKillThread(thread)
#define ts_key_create(ts_key, destructor) \
DosAllocThreadLocalMemory(1, &(ts_key));
#define pthread_getspecific(ts_key) ((void *)(*(ts_key)))
#define pthread_setspecific(ts_key, value) (*(ts_key) = (ULONG)(value))
#define pthread_self() _gettid()
#else
#ifdef __APPLE__
#include <mach/mach_init.h>
#include <mach/semaphore.h>
#include <mach/task.h>
#include <time.h>
#include <unistd.h>
#else
#include <semaphore.h>
#endif
#include <pthread.h>
/* pthreads */
/* Nearly everything is already defined */
#define THREAD_FUNCTION void *
#define THREAD_FUNCTION_RETURN void *
#define THREAD_SPECIFIC_INDEX pthread_key_t
#define ts_key_create(ts_key, destructor) \
pthread_key_create(&(ts_key), destructor);
#endif
/* Synchronization macros: Win32 and Pthreads */
#if defined(_WIN32) && !HAVE_PTHREAD_H
#define sem_t HANDLE
#define pause(voidpara) __asm PAUSE
#define sem_init(sem, sem_attr1, sem_init_value) \
(int)((*sem = CreateSemaphore(NULL, 0, 32768, NULL)) == NULL)
#define sem_wait(sem) \
(int)(WAIT_OBJECT_0 != WaitForSingleObject(*sem, INFINITE))
#define sem_post(sem) ReleaseSemaphore(*sem, 1, NULL)
#define sem_destroy(sem) \
if (*sem) ((int)(CloseHandle(*sem)) == TRUE)
#define thread_sleep(nms) Sleep(nms)
#elif defined(__OS2__)
typedef struct {
HEV event;
HMTX wait_mutex;
HMTX count_mutex;
int count;
} sem_t;
static inline int sem_init(sem_t *sem, int pshared, unsigned int value) {
DosCreateEventSem(NULL, &sem->event, pshared ? DC_SEM_SHARED : 0,
value > 0 ? TRUE : FALSE);
DosCreateMutexSem(NULL, &sem->wait_mutex, 0, FALSE);
DosCreateMutexSem(NULL, &sem->count_mutex, 0, FALSE);
sem->count = value;
return 0;
}
static inline int sem_wait(sem_t *sem) {
DosRequestMutexSem(sem->wait_mutex, -1);
DosWaitEventSem(sem->event, -1);
DosRequestMutexSem(sem->count_mutex, -1);
sem->count--;
if (sem->count == 0) {
ULONG post_count;
DosResetEventSem(sem->event, &post_count);
}
DosReleaseMutexSem(sem->count_mutex);
DosReleaseMutexSem(sem->wait_mutex);
return 0;
}
static inline int sem_post(sem_t *sem) {
DosRequestMutexSem(sem->count_mutex, -1);
if (sem->count < 32768) {
sem->count++;
DosPostEventSem(sem->event);
}
DosReleaseMutexSem(sem->count_mutex);
return 0;
}
static inline int sem_destroy(sem_t *sem) {
DosCloseEventSem(sem->event);
DosCloseMutexSem(sem->wait_mutex);
DosCloseMutexSem(sem->count_mutex);
return 0;
}
#define thread_sleep(nms) DosSleep(nms)
#else
#ifdef __APPLE__
#define sem_t semaphore_t
#define sem_init(X, Y, Z) \
semaphore_create(mach_task_self(), X, SYNC_POLICY_FIFO, Z)
#define sem_wait(sem) (semaphore_wait(*sem))
#define sem_post(sem) semaphore_signal(*sem)
#define sem_destroy(sem) semaphore_destroy(mach_task_self(), *sem)
#define thread_sleep(nms)
/* { struct timespec ts;ts.tv_sec=0; ts.tv_nsec =
1000*nms;nanosleep(&ts, NULL);} */
#else
#include <unistd.h>
#include <sched.h>
#define thread_sleep(nms) sched_yield();
/* {struct timespec ts;ts.tv_sec=0;
ts.tv_nsec = 1000*nms;nanosleep(&ts, NULL);} */
#endif
/* Not Windows. Assume pthreads */
#endif
#if ARCH_X86 || ARCH_X86_64
#include "vpx_ports/x86.h"
#else
#define x86_pause_hint()
#endif
#if defined(__has_feature)
#if __has_feature(thread_sanitizer)
#define USE_MUTEX_LOCK 1
#endif
#endif
#include "vpx_util/vpx_thread.h"
static INLINE int protected_read(pthread_mutex_t *const mutex, const int *p) {
(void)mutex;
#if defined(USE_MUTEX_LOCK)
int ret;
pthread_mutex_lock(mutex);
ret = *p;
pthread_mutex_unlock(mutex);
return ret;
#endif
return *p;
}
static INLINE void sync_read(pthread_mutex_t *const mutex, int mb_col,
const int *last_row_current_mb_col,
const int nsync) {
while (mb_col > (protected_read(mutex, last_row_current_mb_col) - nsync)) {
x86_pause_hint();
thread_sleep(0);
}
}
static INLINE void protected_write(pthread_mutex_t *mutex, int *p, int v) {
(void)mutex;
#if defined(USE_MUTEX_LOCK)
pthread_mutex_lock(mutex);
*p = v;
pthread_mutex_unlock(mutex);
return;
#endif
*p = v;
}
#undef USE_MUTEX_LOCK
#endif /* CONFIG_OS_SUPPORT && CONFIG_MULTITHREAD */
#ifdef __cplusplus
} // extern "C"
#endif
#endif // VP8_COMMON_THREADING_H_
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