Mesa (master): egl: Revisit global data locking.

[Chia-I Wu]

Module: Mesa
Branch: master
Commit: 4afe24808ee253c44c65b855f65bd0749c1e1524
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=4afe24808ee253c44c65b855f65bd0749c1e1524

Author: Chia-I Wu <olv at lunarg.com>
Date:   Wed Feb 17 19:03:30 2010 +0800

egl: Revisit global data locking.

Lock the global mutex in _eglPreloadDrivers and _eglAllocScreenHandle.
Add comments to why certain pathes do not need locking.

---

 src/egl/main/egldriver.c  |   15 ++++++++++++++-
 src/egl/main/eglglobals.h |    1 +
 src/egl/main/eglscreen.c  |   11 ++++++++---
 src/egl/main/eglscreen.h  |    4 ----
 4 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/src/egl/main/egldriver.c b/src/egl/main/egldriver.c
index a87c697..8748fe5 100644
--- a/src/egl/main/egldriver.c
+++ b/src/egl/main/egldriver.c
@@ -237,6 +237,10 @@ _eglMatchDriver(_EGLDisplay *dpy)
    _EGLDriver *best_drv = NULL;
    EGLint best_score = -1, i;
 
+   /*
+    * this function is called after preloading and the drivers never change
+    * after preloading.
+    */
    for (i = 0; i < _eglGlobal.NumDrivers; i++) {
       _EGLDriver *drv = _eglGlobal.Drivers[i];
       EGLint score;
@@ -529,14 +533,21 @@ _eglPreloadDrivers(void)
 {
    EGLBoolean loaded;
 
+   /* protect the preloading process */
+   _eglLockMutex(_eglGlobal.Mutex);
+
    /* already preloaded */
-   if (_eglGlobal.NumDrivers)
+   if (_eglGlobal.NumDrivers) {
+      _eglUnlockMutex(_eglGlobal.Mutex);
       return EGL_TRUE;
+   }
 
    loaded = (_eglPreloadUserDriver() ||
              _eglPreloadDisplayDrivers() ||
              _eglPreloadDefaultDriver());
 
+   _eglUnlockMutex(_eglGlobal.Mutex);
+
    return loaded;
 }
 
@@ -548,6 +559,8 @@ void
 _eglUnloadDrivers(void)
 {
    EGLint i;
+
+   /* this is called at atexit time */
    for (i = 0; i < _eglGlobal.NumDrivers; i++) {
       _EGLDriver *drv = _eglGlobal.Drivers[i];
       lib_handle handle = drv->LibHandle;
diff --git a/src/egl/main/eglglobals.h b/src/egl/main/eglglobals.h
index cd1dd58..4368898 100644
--- a/src/egl/main/eglglobals.h
+++ b/src/egl/main/eglglobals.h
@@ -18,6 +18,7 @@ struct _egl_global
 
    EGLScreenMESA FreeScreenHandle;
 
+   /* these never change after preloading */
    EGLint NumDrivers;
    _EGLDriver *Drivers[10];
 
diff --git a/src/egl/main/eglscreen.c b/src/egl/main/eglscreen.c
index 97a405a..c47afd6 100644
--- a/src/egl/main/eglscreen.c
+++ b/src/egl/main/eglscreen.c
@@ -22,17 +22,22 @@
 #include "eglconfig.h"
 #include "eglsurface.h"
 #include "eglscreen.h"
+#include "eglmutex.h"
 
 
 /**
  * Return a new screen handle/ID.
  * NOTE: we never reuse these!
  */
-EGLScreenMESA
+static EGLScreenMESA
 _eglAllocScreenHandle(void)
 {
-   EGLScreenMESA s = _eglGlobal.FreeScreenHandle;
-   _eglGlobal.FreeScreenHandle++;
+   EGLScreenMESA s;
+   
+   _eglLockMutex(_eglGlobal.Mutex);
+   s = _eglGlobal.FreeScreenHandle++;
+   _eglUnlockMutex(_eglGlobal.Mutex);
+
    return s;
 }
 
diff --git a/src/egl/main/eglscreen.h b/src/egl/main/eglscreen.h
index c400ac3..0fd71f7 100644
--- a/src/egl/main/eglscreen.h
+++ b/src/egl/main/eglscreen.h
@@ -29,10 +29,6 @@ struct _egl_screen
 };
 
 
-extern EGLScreenMESA
-_eglAllocScreenHandle(void);
-
-
 PUBLIC void
 _eglInitScreen(_EGLScreen *screen);