shithub: libvpx

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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

--- a/build/make/rtcd.sh

+++ b/build/make/rtcd.sh

@@ -211,6 +211,8 @@

 $(process_forward_decls)

 $(declare_function_pointers c $ALL_ARCHS)

+

+void ${symbol:-rtcd}(void);

 EOF

 }

@@ -231,11 +233,10 @@

   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 @@

 $(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 @@

 $(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)

 }

--- a/vp8/common/generic/systemdependent.c

+++ b/vp8/common/generic/systemdependent.c

@@ -83,57 +83,6 @@

 #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 @@

 #elif ARCH_X86 || ARCH_X86_64

     ctx->cpu_caps = x86_simd_caps();

 #endif

-

-    once(vpx_rtcd);

 }

--- a/vp8/common/rtcd.c

+++ b/vp8/common/rtcd.c

@@ -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);

+}

--- a/vp8/vp8_cx_iface.c

+++ b/vp8/vp8_cx_iface.c

@@ -9,6 +9,7 @@

  */

+#include "vpx_rtcd.h"

 #include "vpx/vpx_codec.h"

 #include "vpx/internal/vpx_codec_internal.h"

 #include "vpx_version.h"

@@ -571,6 +572,8 @@

     unsigned int               i;

     struct VP8_COMP *optr;

+

+    vpx_rtcd();

     if (!ctx->priv)

     {

--- a/vp8/vp8_dx_iface.c

+++ b/vp8/vp8_dx_iface.c

@@ -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"

@@ -186,6 +187,8 @@

 {

     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

--- a/vpx/vpx_decoder.h

+++ b/vpx/vpx_decoder.h

@@ -113,6 +113,10 @@

      * 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.

--- a/vpx/vpx_encoder.h

+++ b/vpx/vpx_encoder.h

@@ -655,6 +655,10 @@

      * 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.

-- 

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