[PATCH xserver] glamor: Fix crash when master gpu is using glamor and another gpu is hotplugged

[Hans de Goede]

When a GPU gets hotplugged while X is already running, glamor_egl_init()
gets called and changes the current egl context at a point where glamor
does not expect this.

This causes glamor to e.g. crash in the next glamor_create_pixmap() call
(caled through the master's screen->CreatePixmap), note this is not the
only troublesome entry point I've seen other backtraces when using a
composting window manager.

Adding glamor_make_current calls to all entry points is quite expensive,
so this commit consists of a miminal fix for this problem by restoring the
original egl context when leaving glamor_egl_init() with an error, based
on only usb gpu's getting hotplugged and they do not support glamor.

Signed-off-by: Hans de Goede <hdegoede at redhat.com>
---
 glamor/glamor_egl.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/glamor/glamor_egl.c b/glamor/glamor_egl.c
index 16a20a7..ba26e48 100644
--- a/glamor/glamor_egl.c
+++ b/glamor/glamor_egl.c
@@ -731,6 +731,8 @@ glamor_egl_init(ScrnInfoPtr scrn, int fd)
 {
     struct glamor_egl_screen_private *glamor_egl;
     const char *version;
+    EGLDisplay orig_display;
+    EGLContext orig_context;
 
     EGLint config_attribs[] = {
 #ifdef GLAMOR_GLES2
@@ -748,6 +750,9 @@ glamor_egl_init(ScrnInfoPtr scrn, int fd)
         EGL_NONE
     };
 
+    orig_display = eglGetCurrentDisplay();
+    orig_context = eglGetCurrentContext();
+
     glamor_identify(0);
     glamor_egl = calloc(sizeof(*glamor_egl), 1);
     if (glamor_egl == NULL)
@@ -850,6 +855,11 @@ glamor_egl_init(ScrnInfoPtr scrn, int fd)
 
 error:
     glamor_egl_cleanup(glamor_egl);
+    /*
+     * Restore original egl display & context to avoid crashes on
+     * hotplugging USB display devices.
+     */
+    eglMakeCurrent(orig_display, EGL_NO_SURFACE, EGL_NO_SURFACE, orig_context);
     return FALSE;
 }
 
-- 
2.9.3