On Mon, Jul 13, 2009 at 03:14:37PM +0100, José Fonseca wrote:
> Your patches look good, with the exception of relying on
> _glthread_DECLARE_STATIC_MUTEX which is broken on windows, and windows
> too fits on the THREADS && !GLX_USE_TLS use case.
Oops...
>
> So we need to fix _glthread_DECLARE_STATIC_MUTEX on windows first, or
> these lines should be added
>
> #ifdef _WIN32
> /* FIXME: _glthread_DECLARE_STATIC_MUTEX is broken on windows */
> static int onetime = 0;
> if(!onetime) {
> _glthread_INIT_MUTEX(ThreadCheckMutex);
> onetime = 1;
> }
> #endif
>
> Which re-introduces the race condition, but at least it prevents it from
> crashing on the first access to the ThreadCheckMutex. This until we find
> a proper way of implementing _glthread_DECLARE_STATIC_MUTEX on windows.
MSDN says that the behavior is undefined if a critical section is
initialized twice. It is better to avoid the lock completely on
windows. I have attached a patch for this. Could you help me test it?
> Michal, I recall you mentioned some way of statically initializing
> CRITICAL_SECTIONs on windows, but I can't find anything on it on google.
> The only ways I can find are either using atomic operations on a flag,
> or using constructors/DLL_PROCESS_ATTACH etc.
--
Regards,
olv
>From 7cb1560ae640d0a36434ccc926869c417b0f05fa Mon Sep 17 00:00:00 2001
From: Chia-I Wu <olva...@gmail.com>
Date: Tue, 14 Jul 2009 13:17:25 +0800
Subject: [PATCH] Static mutex does not work on WIN32_THREADS.
This re-introduces the race in _glapi_check_multithread, but avoids a
crash on windows.
Signed-off-by: Chia-I Wu <olva...@gmail.com>
---
src/mesa/glapi/glapi.c | 13 +++++++++++--
1 files changed, 11 insertions(+), 2 deletions(-)
diff --git a/src/mesa/glapi/glapi.c b/src/mesa/glapi/glapi.c
index 60b0299..2f90734 100644
--- a/src/mesa/glapi/glapi.c
+++ b/src/mesa/glapi/glapi.c
@@ -195,7 +195,16 @@ GLboolean _glapi_SingleThreaded = GL_FALSE;
#if defined(THREADS)
+#ifdef WIN32_THREADS
+/* _glthread_DECLARE_STATIC_MUTEX is broken on windows. There will be race! */
+#define CHECK_MULTITHREAD_LOCK()
+#define CHECK_MULTITHREAD_UNLOCK()
+#else
_glthread_DECLARE_STATIC_MUTEX(ThreadCheckMutex);
+#define CHECK_MULTITHREAD_LOCK() _glthread_LOCK_MUTEX(ThreadCheckMutex)
+#define CHECK_MULTITHREAD_UNLOCK() _glthread_UNLOCK_MUTEX(ThreadCheckMutex)
+#endif
+
GLboolean _glapi_SingleThreaded = GL_TRUE; /**< In single-thread mode? */
_glthread_TSD _gl_DispatchTSD; /**< Per-thread dispatch pointer */
static _glthread_TSD ContextTSD; /**< Per-thread context pointer */
@@ -235,7 +244,7 @@ _glapi_check_multithread(void)
if (!_glapi_SingleThreaded)
return;
- _glthread_LOCK_MUTEX(ThreadCheckMutex);
+ CHECK_MULTITHREAD_LOCK();
if (firstCall) {
/* initialize TSDs */
(void) _glthread_GetTSD(&ContextTSD);
@@ -252,7 +261,7 @@ _glapi_check_multithread(void)
*/
_glapi_SingleThreaded = GL_FALSE;
}
- _glthread_UNLOCK_MUTEX(ThreadCheckMutex);
+ CHECK_MULTITHREAD_UNLOCK();
#endif
}
--
1.6.2.4
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