fix a race condition in eglMakeCurrent()

it would happen when a context was made non-current, in this
case we would call the implementation's eglMakeCurrent() which
would succeed, if we're rescheduled at that point, another
eglMakeCurrent() could make that context current to another thread,
however, when we came back to the original call we would
overwrite egl_context_t internal state.

this is fixed by moving the critical section under
egl_display_t's lock.

Change-Id: I743c85696e13263d3a9570824940263df0caacdc

1 files changed, 41 insertions, 0 deletions

diff --git a/opengl/libs/EGL/egl_display.cpp b/opengl/libs/EGL/egl_display.cpp
index 53eaf9a..5cf5236 100644
--- a/opengl/libs/EGL/egl_display.cpp
+++ b/opengl/libs/EGL/egl_display.cpp
@@ -342,6 +342,47 @@ EGLBoolean egl_display_t::terminate() {
     return res;
 }
 
+void egl_display_t::loseCurrent(egl_context_t * cur_c)
+{
+    if (cur_c) {
+        egl_surface_t * cur_r = get_surface(cur_c->read);
+        egl_surface_t * cur_d = get_surface(cur_c->draw);
+
+        // by construction, these are either 0 or valid (possibly terminated)
+        // it should be impossible for these to be invalid
+        ContextRef _cur_c(cur_c);
+        SurfaceRef _cur_r(cur_r);
+        SurfaceRef _cur_d(cur_d);
+
+        cur_c->onLooseCurrent();
+
+        _cur_c.release();
+        _cur_r.release();
+        _cur_d.release();
+    }
+}
+
+EGLBoolean egl_display_t::makeCurrent(egl_context_t* c, egl_context_t* cur_c,
+        EGLSurface draw, EGLSurface read, EGLContext ctx,
+        EGLSurface impl_draw, EGLSurface impl_read, EGLContext impl_ctx)
+{
+    Mutex::Autolock _l(lock);
+    EGLBoolean result;
+    if (c) {
+        result = c->cnx->egl.eglMakeCurrent(
+                disp[c->impl].dpy, impl_draw, impl_read, impl_ctx);
+    } else {
+        result = cur_c->cnx->egl.eglMakeCurrent(
+                disp[cur_c->impl].dpy, impl_draw, impl_read, impl_ctx);
+    }
+    if (result == EGL_TRUE) {
+        loseCurrent(cur_c);
+        if (c) {
+            c->onMakeCurrent(draw, read);
+        }
+    }
+    return result;
+}
 
 // ----------------------------------------------------------------------------
 }; // namespace android