On Tue, Sep 26, 2017 at 10:38 AM, Julia Lawall <julia.lawall@xxxxxxx> 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@xxxxxxxxx>
>>
>> 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.
-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
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