Hi Daniel,
(On a side note, git-format-patch accepts a -v argument to specify the
version, I didn't realize you were not aware of it :-))
On Mon, Mar 23, 2020 at 03:49:18PM +0100, Daniel Vetter wrote:
> A few things:
> - Update the example driver in the documentation.
> - We can drop the old kfree in drm_dev_release.
> - Add a WARN_ON check in drm_dev_register to make sure everyone calls
> drmm_add_final_kfree and there's no leaks.
>
> v2: Restore the full cleanup, I accidentally left some moved code
> behind when fixing the bisectability of the series.
>
> Acked-by: Sam Ravnborg <sam@xxxxxxxxxxxx>
> Acked-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
> Cc: Sam Ravnborg <sam@xxxxxxxxxxxx>
> Cc: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
> ---
> drivers/gpu/drm/drm_drv.c | 12 +++++-------
> 1 file changed, 5 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index 877ded348b6e..7f9d7ea543a0 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -297,8 +297,6 @@ void drm_minor_release(struct drm_minor *minor)
> *
> * drm_mode_config_cleanup(drm);
> * drm_dev_fini(drm);
> - * kfree(priv->userspace_facing);
> - * kfree(priv);
> * }
> *
> * static struct drm_driver driver_drm_driver = {
> @@ -326,10 +324,11 @@ void drm_minor_release(struct drm_minor *minor)
> * kfree(drm);
> * return ret;
> * }
> + * drmm_add_final_kfree(drm, priv);
> *
> * drm_mode_config_init(drm);
> *
> - * priv->userspace_facing = kzalloc(..., GFP_KERNEL);
> + * priv->userspace_facing = drmm_kzalloc(..., GFP_KERNEL);
> * if (!priv->userspace_facing)
> * return -ENOMEM;
> *
> @@ -837,10 +836,7 @@ static void drm_dev_release(struct kref *ref)
>
> drm_managed_release(dev);
>
> - if (!dev->driver->release && !dev->managed.final_kfree) {
> - WARN_ON(!list_empty(&dev->managed.resources));
> - kfree(dev);
> - } else if (dev->managed.final_kfree)
> + if (dev->managed.final_kfree)
> kfree(dev->managed.final_kfree);
> }
>
> @@ -961,6 +957,8 @@ int drm_dev_register(struct drm_device *dev, unsigned long flags)
> if (!driver->load)
> drm_mode_config_validate(dev);
>
> + WARN_ON(!dev->managed.final_kfree);
That's too aggressive. Driver freeing their private object in .release()
isn't wrong. I'd even go as far as saying that it should be the norm,
until we manage to find a better way to handle that (which this series
doesn't achieve). Many drivers need to allocate resources at probe time
before they get a chance to init the drm device. Those resources must be
released in the error handling paths of probe. By requiring
drmm_add_final_kfree(), you're making that much more complex. I can't
release those resources in the error path anymore after calling
drmm_add_final_kfree(), or they will be released twice. And I can't rely
on drmm_* to release them in all cases, as the error path may be hit
before touching anything drm-related.
Until we figure out a good way forward and test it on a significant
number of drivers, let's not add WARN_ON() that will be hit with the
majority of drivers, forcing them to be converted to something that is
clearly half-baked.
> +
> if (drm_dev_needs_global_mutex(dev))
> mutex_lock(&drm_global_mutex);
>
--
Regards,
Laurent Pinchart
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