On 13.06.2017 16:43, Thierry Reding wrote:

On Tue, May 23, 2017 at 03:14:22AM +0300, Dmitry Osipenko wrote:

quoted

The framebuffers console fbcon_startup() increments the tegra_drm module
'use' refcount via try_module_get(), causing an interlock of the DRM subsys
and the tegra_drm modules. In result, the tegra_drm module can't be unloaded
using rmmod.

Signed-off-by: Dmitry Osipenko <redacted>
---
 drivers/gpu/drm/tegra/fb.c | 1 -
 1 file changed, 1 deletion(-)

That's done on purpose because otherwise you could just rip out the
driver from under the framebuffer emulation and things would crash.

My understanding is that the right way to unload a module is to unbind
the driver first (which will cause the framebuffer to be removed and
hence the reference to be dropped) before the rmmod.

Thierry

Aha, interesting. I'll try the unbinding and will drop this patch from the
series, thank you for the clarification. I haven't observed any crashes on a
module reloading (framebuffer detached/attached just fine), maybe I was lucky then.

-- 
Dmitry