Re: [PATCH v19 09/30] drm/shmem-helper: Add and use lockless drm_gem_shmem_get_pages()

[Dmitry Osipenko]

On 1/25/24 20:24, Daniel Vetter wrote:
> On Fri, Jan 05, 2024 at 09:46:03PM +0300, Dmitry Osipenko wrote:
>> Add lockless drm_gem_shmem_get_pages() helper that skips taking reservation
>> lock if pages_use_count is non-zero, leveraging from atomicity of the
>> refcount_t. Make drm_gem_shmem_mmap() to utilize the new helper.
>>
>> Acked-by: Maxime Ripard <mripard@xxxxxxxxxx>
>> Reviewed-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
>> Suggested-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
>> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
>> ---
>>  drivers/gpu/drm/drm_gem_shmem_helper.c | 19 +++++++++++++++----
>>  1 file changed, 15 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
>> index cacf0f8c42e2..1c032513abf1 100644
>> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
>> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
>> @@ -226,6 +226,20 @@ void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem)
>>  }
>>  EXPORT_SYMBOL_GPL(drm_gem_shmem_put_pages_locked);
>>  
>> +static int drm_gem_shmem_get_pages(struct drm_gem_shmem_object *shmem)
>> +{
>> +	int ret;
> 
> Just random drive-by comment: a might_lock annotation here might be good,
> or people could hit some really interesting bugs that are rather hard to
> reproduce ...
> -Sima

Thanks for the suggestion!

-- 
Best regards,
Dmitry