Re: [PATCH] drm/radeon: don't add files at control minor debugfs directory

[Christian KÃnig]

Am 05.12.2016 um 08:27 schrieb Daniel Vetter:
> On Sat, Dec 03, 2016 at 03:47:00PM +0100, Nicolai Stange wrote:
> > Since commit 8a357d10043c ("drm: Nerf DRM_CONTROL nodes"), a
> > struct drm_device's ->control member is always NULL.
> >
> > In the case of CONFIG_DEBUG_FS=y, radeon_debugfs_add_files() accesses
> > ->control->debugfs_root though. This results in the following Oops:
> >
> >    BUG: unable to handle kernel NULL pointer dereference at 0000000000000018
> >    IP: radeon_debugfs_add_files+0x90/0x100 [radeon]
> >    PGD 0
> >    Oops: 0000 [#1] SMP
> >    [...]
> >    Call Trace:
> >     ? work_on_cpu+0xb0/0xb0
> >     radeon_fence_driver_init+0x120/0x150 [radeon]
> >     si_init+0x122/0xd50 [radeon]
> >     ? _raw_spin_unlock_irq+0x2c/0x40
> >     ? device_pm_check_callbacks+0xb3/0xc0
> >     radeon_device_init+0x958/0xda0 [radeon]
> >     radeon_driver_load_kms+0x9a/0x210 [radeon]
> >     drm_dev_register+0xa9/0xd0 [drm]
> >     drm_get_pci_dev+0x9c/0x1e0 [drm]
> >     radeon_pci_probe+0xb8/0xe0 [radeon]
> >    [...]
> >
> > Fix this by omitting the drm_debugfs_create_files() call for the
> > control minor debugfs directory which is now non-existent anyway.
> >
> > Fixes: 8a357d10043c ("drm: Nerf DRM_CONTROL nodes")
> > Signed-off-by: Nicolai Stange <nicstange@xxxxxxxxx>
> Applied to drm-misc with Dave's irc ack, thanks for your patch.

If it's still worth it the patch is Reviewed-by: Christian König 
<christian.koenig@xxxxxxx>.

On the other hand when ->control is always NULL, why do we still have 
->control anyway?

And BTW: Please double check the other drivers as well.

Regards,
Christian.

> -Daniel
>
> > ---
> > Tested on top of next-20161202.
> > That 8a357d10043c ("drm: Nerf DRM_CONTROL nodes")
> > is in next since 20161201.
> >
> >   drivers/gpu/drm/radeon/radeon_device.c | 6 ------
> >   1 file changed, 6 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/radeon/radeon_device.c b/drivers/gpu/drm/radeon/radeon_device.c
> > index 60a8920..8a1df2a 100644
> > --- a/drivers/gpu/drm/radeon/radeon_device.c
> > +++ b/drivers/gpu/drm/radeon/radeon_device.c
> > @@ -1949,9 +1949,6 @@ int radeon_debugfs_add_files(struct radeon_device *rdev,
> >   	rdev->debugfs_count = i;
> >   #if defined(CONFIG_DEBUG_FS)
> >   	drm_debugfs_create_files(files, nfiles,
> > -				 rdev->ddev->control->debugfs_root,
> > -				 rdev->ddev->control);
> > -	drm_debugfs_create_files(files, nfiles,
> >   				 rdev->ddev->primary->debugfs_root,
> >   				 rdev->ddev->primary);
> >   #endif
> > @@ -1966,9 +1963,6 @@ static void radeon_debugfs_remove_files(struct radeon_device *rdev)
> >   	for (i = 0; i < rdev->debugfs_count; i++) {
> >   		drm_debugfs_remove_files(rdev->debugfs[i].files,
> >   					 rdev->debugfs[i].num_files,
> > -					 rdev->ddev->control);
> > -		drm_debugfs_remove_files(rdev->debugfs[i].files,
> > -					 rdev->debugfs[i].num_files,
> >   					 rdev->ddev->primary);
> >   	}
> >   #endif
> > --
> > 2.10.2
> >
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