[Mesa-dev] [PATCH v2] egl/dri2: try to bind old context if bindContext failed

[Luigi Santivetti]

Before this change, if bindContext() failed then dri2_make_current() would
rebind the old EGL context and surfaces and return EGL_BAD_MATCH. However,
it wouldn't rebind the DRI context and surfaces, thus leaving it in an
inconsistent and unrecoverable state.

After this change, dri2_make_current() tries to bind the old DRI context
and surfaces when bindContext() failed. If unable to do so, it leaves EGL
and the DRI driver in a consistent state, it reports an error and returns
EGL_BAD_MATCH.

Fixes: 4e8f95f64d004aa1 ("egl_dri2: Always unbind old contexts")

Signed-off-by: Luigi Santivetti <luigi.santivetti at imgtec.com>
Reviewed-by: Frank Binns <frank.binns at imgtec.com>
---

v2 fixes:
    warning: assignment from incompatible pointer type [-Wincompatible-pointer-types]

gentle ping on this one.
Thanks,

Luigi

 src/egl/drivers/dri2/egl_dri2.c | 55 ++++++++++++++++++++++++++-------
 1 file changed, 44 insertions(+), 11 deletions(-)

diff --git a/src/egl/drivers/dri2/egl_dri2.c b/src/egl/drivers/dri2/egl_dri2.c
index c98b9a5d18a..3c5237eb103 100644
--- a/src/egl/drivers/dri2/egl_dri2.c
+++ b/src/egl/drivers/dri2/egl_dri2.c
@@ -1446,8 +1446,9 @@ dri2_make_current(_EGLDriver *drv, _EGLDisplay *disp, _EGLSurface *dsurf,
    _EGLSurface *old_dsurf, *old_rsurf;
    _EGLSurface *tmp_dsurf, *tmp_rsurf;
    __DRIdrawable *ddraw, *rdraw;
-   __DRIcontext *cctx;
+   __DRIcontext *cctx, *old_cctx;
    EGLBoolean unbind;
+   EGLint egl_error;
 
    if (!dri2_dpy)
       return _eglError(EGL_NOT_INITIALIZED, "eglMakeCurrent");
@@ -1472,7 +1473,7 @@ dri2_make_current(_EGLDriver *drv, _EGLDisplay *disp, _EGLSurface *dsurf,
    cctx = (dri2_ctx) ? dri2_ctx->dri_context : NULL;
 
    if (old_ctx) {
-      __DRIcontext *old_cctx = dri2_egl_context(old_ctx)->dri_context;
+      old_cctx = dri2_egl_context(old_ctx)->dri_context;
 
       if (old_dsurf)
          dri2_surf_update_fence_fd(old_ctx, disp, old_dsurf);
@@ -1489,17 +1490,24 @@ dri2_make_current(_EGLDriver *drv, _EGLDisplay *disp, _EGLSurface *dsurf,
    unbind = (cctx == NULL && ddraw == NULL && rdraw == NULL);
 
    if (!unbind && !dri2_dpy->core->bindContext(cctx, ddraw, rdraw)) {
+      __DRIdrawable *old_ddraw, *old_rdraw;
+
+      /* dri2_dpy->core->bindContext failed. We cannot tell for sure why, but
+       * setting the error to EGL_BAD_MATCH is surely better than leaving it
+       * as EGL_SUCCESS.
+       */
+      egl_error = EGL_BAD_MATCH;
+
+      old_ddraw = (old_dsurf) ? dri2_dpy->vtbl->get_dri_drawable(old_dsurf) : NULL;
+      old_rdraw = (old_rsurf) ? dri2_dpy->vtbl->get_dri_drawable(old_rsurf) : NULL;
+      old_cctx = (old_ctx) ? dri2_egl_context(old_ctx)->dri_context : NULL;
+
       /* undo the previous _eglBindContext */
       _eglBindContext(old_ctx, old_dsurf, old_rsurf, &ctx, &tmp_dsurf, &tmp_rsurf);
       assert(&dri2_ctx->base == ctx &&
              tmp_dsurf == dsurf &&
              tmp_rsurf == rsurf);
 
-      if (old_dsurf && _eglSurfaceInSharedBufferMode(old_dsurf) &&
-          old_dri2_dpy->vtbl->set_shared_buffer_mode) {
-         old_dri2_dpy->vtbl->set_shared_buffer_mode(old_disp, old_dsurf, true);
-      }
-
       _eglPutSurface(dsurf);
       _eglPutSurface(rsurf);
       _eglPutContext(ctx);
@@ -1508,11 +1516,33 @@ dri2_make_current(_EGLDriver *drv, _EGLDisplay *disp, _EGLSurface *dsurf,
       _eglPutSurface(old_rsurf);
       _eglPutContext(old_ctx);
 
-      /* dri2_dpy->core->bindContext failed. We cannot tell for sure why, but
-       * setting the error to EGL_BAD_MATCH is surely better than leaving it
-       * as EGL_SUCCESS.
+      /* undo the previous dri2_dpy->core->unbindContext */
+      if (dri2_dpy->core->bindContext(old_cctx, old_ddraw, old_rdraw)) {
+         if (old_dsurf && _eglSurfaceInSharedBufferMode(old_dsurf) &&
+             old_dri2_dpy->vtbl->set_shared_buffer_mode) {
+            old_dri2_dpy->vtbl->set_shared_buffer_mode(old_disp, old_dsurf, true);
+         }
+
+         return _eglError(egl_error, "eglMakeCurrent");
+      }
+
+      /* We cannot restore the same state as it was before calling
+       * eglMakeCurrent(), but we can keep EGL in a consistent state with
+       * the DRI driver by unbinding the old EGL context and surfaces.
        */
-      return _eglError(EGL_BAD_MATCH, "eglMakeCurrent");
+      ctx = NULL;
+      dsurf = rsurf = NULL;
+      unbind = true;
+
+      _eglBindContext(ctx, dsurf, rsurf, &old_ctx, &tmp_dsurf, &tmp_rsurf);
+      assert(&dri2_ctx->base == old_ctx &&
+             tmp_dsurf == old_dsurf &&
+             tmp_rsurf == old_rsurf);
+
+      _eglLog(_EGL_FATAL, "DRI2: failed to rebind the previous context");
+   } else {
+      /* We can no longer fail at this point. */
+      egl_error = EGL_SUCCESS;
    }
 
    dri2_destroy_surface(drv, disp, old_dsurf);
@@ -1538,6 +1568,9 @@ dri2_make_current(_EGLDriver *drv, _EGLDisplay *disp, _EGLSurface *dsurf,
       dri2_dpy->vtbl->set_shared_buffer_mode(disp, dsurf, mode);
    }
 
+   if (egl_error != EGL_SUCCESS)
+      return _eglError(egl_error, "eglMakeCurrent");
+
    return EGL_TRUE;
 }
 
-- 
2.20.1