From c311b3b3a9ceb0e45e0d5969bb20f1e95dbd9059 Mon Sep 17 00:00:00 2001 From: John Koleszar Date: Wed, 18 Apr 2012 16:03:40 -0700 Subject: [PATCH] rtcd: serialize function pointer initialization Ensure that RTCD function pointers are set at most once, to silence some data race warnings. Implementation provided for POSIX threads and Win32, with the prior unsynchronized behavior left in place for other platforms. Change-Id: I65c5856df43ef67043b3d5f26ddafddd8fcb2f7e --- vp8/common/generic/systemdependent.c | 54 +++++++++++++++++++++++++++++++++++- 1 file changed, 53 insertions(+), 1 deletion(-) diff --git a/vp8/common/generic/systemdependent.c b/vp8/common/generic/systemdependent.c index 39660ab..2a30166 100644 --- a/vp8/common/generic/systemdependent.c +++ b/vp8/common/generic/systemdependent.c @@ -82,6 +82,58 @@ static int get_cpu_count() } #endif + +#if HAVE_PTHREAD_H +#include +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 @@ -94,5 +146,5 @@ void vp8_machine_specific_config(VP8_COMMON *ctx) ctx->cpu_caps = x86_simd_caps(); #endif - vpx_rtcd(); + once(vpx_rtcd); } -- 2.7.4