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

1 files changed, 0 insertions, 53 deletions

diff --git a/vp8/common/generic/systemdependent.c b/vp8/common/generic/systemdependent.c
index 2a3016618..5a6ac7b0e 100644
--- a/vp8/common/generic/systemdependent.c
+++ b/vp8/common/generic/systemdependent.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);
 }