[Outreachy kernel] [PATCH] drm/gem: use new idr deletion interface to cleanup drm_gem_handle_delete()

[Daniel Vetter]

On Tue, Sep 26, 2017 at 10:47 AM, Daniel Vetter <daniel at ffwll.ch> wrote:
> On Tue, Sep 26, 2017 at 10:38 AM, Julia Lawall <julia.lawall at lip6.fr> wrote:
>>
>>
>> On Tue, 26 Sep 2017, Daniel Vetter wrote:
>>
>>> On Tue, Sep 26, 2017 at 12:17:28AM +0530, Aishwarya Pant wrote:
>>> > The IDR deletion interface now returns the deleted entry or NULL if it was not
>>> > present. So we don't have to do the extra work of checking if we have a
>>> > reference on the drm_gem_object, this can be handled by checking the return
>>> > value from idr_remove() and the extra locks can be dropped.
>>> >
>>> > Signed-off-by: Aishwarya Pant <aishpant at gmail.com>
>>>
>>> Haneen is already working on this task, with the patch just merged. Please
>>> coordinate with mentors (me or Sean Paul) before starting on something to
>>> avoid such clashes in the future.
>>>
>>> Note also that some todo items are just ideas, and need confirmation with
>>> relevant maintainers first.
>>
>> Not sure where the mixup happened, but anyone who starts on a project
>> specific task should note that on the outreachy kernel wiki and before
>> starting on a project specific task one should check that no one is
>> working on it.  If someone started some time ago, and the code doesn't
>> seem to have changed, ask the person who claimed the task or the mentor.
>
> Hm, the dri-devel tasks aren't on the wiki, but in the kernel sources.
> Where should we put the scratch-pad to avoid such conflicts in the
> future? E.g. the IIO subsytems has it's task on the wiki, where this
> works much better.

Ok, I found it. Looks like a few signed up for stuff, but without
chatting with us first, and ended up picking tasks that need some
serious GPU expertise. I.e. maybe suitable for a full internship,
definitely not as starter tasks. I'll send out mails.
-Daniel


> -Daniel
>
>>
>> thanks,
>>
>> julia
>>
>>>
>>> Thanks, Daniel
>>> > ---
>>> >  drivers/gpu/drm/drm_gem.c | 21 ++-------------------
>>> >  1 file changed, 2 insertions(+), 19 deletions(-)
>>> >
>>> > diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
>>> > index c55f338..f62757a 100644
>>> > --- a/drivers/gpu/drm/drm_gem.c
>>> > +++ b/drivers/gpu/drm/drm_gem.c
>>> > @@ -282,29 +282,12 @@ drm_gem_handle_delete(struct drm_file *filp, u32 handle)
>>> >  {
>>> >     struct drm_gem_object *obj;
>>> >
>>> > -   /* This is gross. The idr system doesn't let us try a delete and
>>> > -    * return an error code.  It just spews if you fail at deleting.
>>> > -    * So, we have to grab a lock around finding the object and then
>>> > -    * doing the delete on it and dropping the refcount, or the user
>>> > -    * could race us to double-decrement the refcount and cause a
>>> > -    * use-after-free later.  Given the frequency of our handle lookups,
>>> > -    * we may want to use ida for number allocation and a hash table
>>> > -    * for the pointers, anyway.
>>> > -    */
>>> >     spin_lock(&filp->table_lock);
>>> > -
>>> > -   /* Check if we currently have a reference on the object */
>>> > -   obj = idr_replace(&filp->object_idr, NULL, handle);
>>> > -   spin_unlock(&filp->table_lock);
>>> > -   if (IS_ERR_OR_NULL(obj))
>>> > +   obj = idr_remove(&filp->object_idr, handle);
>>> > +   if (!obj)
>>> >             return -EINVAL;
>>> > -
>>> >     /* Release driver's reference and decrement refcount. */
>>> >     drm_gem_object_release_handle(handle, obj, filp);
>>> > -
>>> > -   /* And finally make the handle available for future allocations. */
>>> > -   spin_lock(&filp->table_lock);
>>> > -   idr_remove(&filp->object_idr, handle);
>>> >     spin_unlock(&filp->table_lock);
>>> >
>>> >     return 0;
>>> > --
>>> > 2.7.4
>>> >
>>> > --
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>>>
>>> --
>>> Daniel Vetter
>>> Software Engineer, Intel Corporation
>>> http://blog.ffwll.ch
>>>
>>> --
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>>>
>
>
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch



-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch