Commit 8df79e9d authored by John Koleszar's avatar John Koleszar
Browse files

Remove threading dependencies with --disable-multithread

Avoid a pthreads dependency via pthread_once() when compiled with
--disable-multithread.

In addition, this synchronization is disabled for Win32 as well, even
though we can be sure that the required primatives exist, so that the
requirements on the application when built with --disable-multithread
are consistent across platforms.

Users using libvpx built with --disable-multithread in a multithreaded
context should provide their own synchronization. Updated the
documentation to vpx_codec_enc_init_ver() and vpx_codec_dec_init_ver()
to note this requirement. Moved the RTCD initialization call to match
this description, as previously it didn't happen until the first
frame.

Change-Id: Id576f6bce2758362188278d3085051c218a56d4a
parent 0164a1cc
......@@ -211,6 +211,8 @@ common_top() {
$(process_forward_decls)
$(declare_function_pointers c $ALL_ARCHS)
void ${symbol:-rtcd}(void);
EOF
}
......@@ -231,11 +233,10 @@ x86() {
cat <<EOF
$(common_top)
void ${symbol:-rtcd}(void);
#ifdef RTCD_C
#include "vpx_ports/x86.h"
void ${symbol:-rtcd}(void)
static void setup_rtcd_internal(void)
{
int flags = x86_simd_caps();
......@@ -261,11 +262,9 @@ arm() {
$(common_top)
#include "vpx_config.h"
void ${symbol:-rtcd}(void);
#ifdef RTCD_C
#include "vpx_ports/arm.h"
void ${symbol:-rtcd}(void)
static void setup_rtcd_internal(void)
{
int flags = arm_cpu_caps();
......@@ -285,10 +284,8 @@ unoptimized() {
$(common_top)
#include "vpx_config.h"
void ${symbol:-rtcd}(void);
#ifdef RTCD_C
void ${symbol:-rtcd}(void)
static void setup_rtcd_internal(void)
{
$(set_function_pointers c)
}
......
......@@ -83,57 +83,6 @@ static int get_cpu_count()
#endif
#if HAVE_PTHREAD_H
#include <pthread.h>
static void once(void (*func)(void))
{
static pthread_once_t lock = PTHREAD_ONCE_INIT;
pthread_once(&lock, func);
}
#elif defined(_WIN32)
static void once(void (*func)(void))
{
/* Using a static initializer here rather than InitializeCriticalSection()
* since there's no race-free context in which to execute it. Protecting
* it with an atomic op like InterlockedCompareExchangePointer introduces
* an x86 dependency, and InitOnceExecuteOnce requires Vista.
*/
static CRITICAL_SECTION lock = {(void *)-1, -1, 0, 0, 0, 0};
static int done;
EnterCriticalSection(&lock);
if (!done)
{
func();
done = 1;
}
LeaveCriticalSection(&lock);
}
#else
/* No-op version that performs no synchronization. vpx_rtcd() is idempotent,
* so as long as your platform provides atomic loads/stores of pointers
* no synchronization is strictly necessary.
*/
static void once(void (*func)(void))
{
static int done;
if(!done)
{
func();
done = 1;
}
}
#endif
void vp8_machine_specific_config(VP8_COMMON *ctx)
{
#if CONFIG_MULTITHREAD
......@@ -145,6 +94,4 @@ void vp8_machine_specific_config(VP8_COMMON *ctx)
#elif ARCH_X86 || ARCH_X86_64
ctx->cpu_caps = x86_simd_caps();
#endif
once(vpx_rtcd);
}
......@@ -10,3 +10,60 @@
#include "vpx_config.h"
#define RTCD_C
#include "vpx_rtcd.h"
#if CONFIG_MULTITHREAD && HAVE_PTHREAD_H
#include <pthread.h>
static void once(void (*func)(void))
{
static pthread_once_t lock = PTHREAD_ONCE_INIT;
pthread_once(&lock, func);
}
#elif CONFIG_MULTITHREAD && defined(_WIN32)
#include <windows.h>
static void once(void (*func)(void))
{
/* Using a static initializer here rather than InitializeCriticalSection()
* since there's no race-free context in which to execute it. Protecting
* it with an atomic op like InterlockedCompareExchangePointer introduces
* an x86 dependency, and InitOnceExecuteOnce requires Vista.
*/
static CRITICAL_SECTION lock = {(void *)-1, -1, 0, 0, 0, 0};
static int done;
EnterCriticalSection(&lock);
if (!done)
{
func();
done = 1;
}
LeaveCriticalSection(&lock);
}
#else
/* No-op version that performs no synchronization. vpx_rtcd() is idempotent,
* so as long as your platform provides atomic loads/stores of pointers
* no synchronization is strictly necessary.
*/
static void once(void (*func)(void))
{
static int done;
if(!done)
{
func();
done = 1;
}
}
#endif
void vpx_rtcd()
{
once(setup_rtcd_internal);
}
......@@ -9,6 +9,7 @@
*/
#include "vpx_rtcd.h"
#include "vpx/vpx_codec.h"
#include "vpx/internal/vpx_codec_internal.h"
#include "vpx_version.h"
......@@ -572,6 +573,8 @@ static vpx_codec_err_t vp8e_init(vpx_codec_ctx_t *ctx,
struct VP8_COMP *optr;
vpx_rtcd();
if (!ctx->priv)
{
priv = calloc(1, sizeof(struct vpx_codec_alg_priv));
......
......@@ -11,6 +11,7 @@
#include <stdlib.h>
#include <string.h>
#include "vpx_rtcd.h"
#include "vpx/vpx_decoder.h"
#include "vpx/vp8dx.h"
#include "vpx/internal/vpx_codec_internal.h"
......@@ -187,6 +188,8 @@ static vpx_codec_err_t vp8_init(vpx_codec_ctx_t *ctx,
vpx_codec_err_t res = VPX_CODEC_OK;
(void) data;
vpx_rtcd();
/* This function only allocates space for the vpx_codec_alg_priv_t
* structure. More memory may be required at the time the stream
* information becomes known.
......
......@@ -113,6 +113,10 @@ extern "C" {
* function directly, to ensure that the ABI version number parameter
* is properly initialized.
*
* If the library was configured with --disable-multithread, this call
* is not thread safe and should be guarded with a lock if being used
* in a multithreaded context.
*
* In XMA mode (activated by setting VPX_CODEC_USE_XMA in the flags
* parameter), the storage pointed to by the cfg parameter must be
* kept readable and stable until all memory maps have been set.
......
......@@ -655,6 +655,10 @@ extern "C" {
* function directly, to ensure that the ABI version number parameter
* is properly initialized.
*
* If the library was configured with --disable-multithread, this call
* is not thread safe and should be guarded with a lock if being used
* in a multithreaded context.
*
* In XMA mode (activated by setting VPX_CODEC_USE_XMA in the flags
* parameter), the storage pointed to by the cfg parameter must be
* kept readable and stable until all memory maps have been set.
......
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment