Re: [PATCH] drm/sysfs: Do not drop device reference twice

From: Thierry Reding
Date: Wed Oct 30 2013 - 17:18:23 EST

On Wed, Oct 30, 2013 at 02:05:02PM -0200, Paulo Zanoni wrote:
> 2013/10/30 Thierry Reding <thierry.reding@xxxxxxxxx>:
> > device_unregister() already drops its reference to the struct device, so
> > explicitly calling put_device() before device_unregister() can cause the
> > device to have been freed before it can be unregistered.
> >
> > Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
> I started investigating this problem yesterday and reached the same
> conclusion. The connector path can be easily reproduced on i915.ko:
> get a machine that has an eDP panel, physically disconnect the panel,
> boot the machine, "modprobe i915" and watch the segfault.
> Reviewed-by: Paulo Zanoni <paulo.r.zanoni@xxxxxxxxx>
> Tested-by: Paulo Zanoni <paulo.r.zanoni@xxxxxxxxx>
> I didn't really bisect, but I believe this is probably a regression
> from "drm/sysfs: sort out minor and connector device object
> lifetimes".

Yes, I think that's the one that broke it.


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