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

[Eric Anholt]

Hans de Goede <hdegoede at redhat.com> writes:

> 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.

I think the problem is just mismatching our lastGLContext with the
actual makecurrent state.  Couldn't we just use glamor_make_current()
instead of our own eglMakeCurrent() call in this function?
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