[PATCH 4/6] drm/amdkfd: GFP_NOIO while holding locks taken in MMU notifier

[Oded Gabbay]

On Fri, Mar 23, 2018 at 10:32 PM, Felix Kuehling <Felix.Kuehling at amd.com> wrote:
> When an MMU notifier runs in memory reclaim context, it can deadlock
> trying to take locks that are already held in the thread causing the
> memory reclaim. The solution is to avoid memory reclaim while holding
> locks that are taken in MMU notifiers by using GFP_NOIO.

Which locks are problematic ?

The kernel recommendation is to use "memalloc_noio_{save,restore} to
mark the whole scope which cannot perform any IO with a short
explanation why"

By using the scope functions, you protect against future allocation
code that will be written in the critical path, without worrying about
the developer using the correct GFP_NOIO flag.

Oded

>
> This commit fixes memory allocations done while holding the dqm->lock
> which is needed in the MMU notifier (dqm->ops.evict_process_queues).
>
> Signed-off-by: Felix Kuehling <Felix.Kuehling at amd.com>
> ---
>  drivers/gpu/drm/amd/amdkfd/kfd_device.c          | 2 +-
>  drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_cik.c | 2 +-
>  drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_vi.c  | 2 +-
>  3 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_device.c b/drivers/gpu/drm/amd/amdkfd/kfd_device.c
> index 334669996..0434f65 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_device.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_device.c
> @@ -652,7 +652,7 @@ int kfd_gtt_sa_allocate(struct kfd_dev *kfd, unsigned int size,
>         if (size > kfd->gtt_sa_num_of_chunks * kfd->gtt_sa_chunk_size)
>                 return -ENOMEM;
>
> -       *mem_obj = kmalloc(sizeof(struct kfd_mem_obj), GFP_KERNEL);
> +       *mem_obj = kmalloc(sizeof(struct kfd_mem_obj), GFP_NOIO);
>         if ((*mem_obj) == NULL)
>                 return -ENOMEM;
>
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_cik.c b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_cik.c
> index c00c325..2bc49c6 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_cik.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_cik.c
> @@ -412,7 +412,7 @@ struct mqd_manager *mqd_manager_init_cik(enum KFD_MQD_TYPE type,
>         if (WARN_ON(type >= KFD_MQD_TYPE_MAX))
>                 return NULL;
>
> -       mqd = kzalloc(sizeof(*mqd), GFP_KERNEL);
> +       mqd = kzalloc(sizeof(*mqd), GFP_NOIO);
>         if (!mqd)
>                 return NULL;
>
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_vi.c b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_vi.c
> index 89e4242..481307b 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_vi.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_vi.c
> @@ -394,7 +394,7 @@ struct mqd_manager *mqd_manager_init_vi(enum KFD_MQD_TYPE type,
>         if (WARN_ON(type >= KFD_MQD_TYPE_MAX))
>                 return NULL;
>
> -       mqd = kzalloc(sizeof(*mqd), GFP_KERNEL);
> +       mqd = kzalloc(sizeof(*mqd), GFP_NOIO);
>         if (!mqd)
>                 return NULL;
>
> --
> 2.7.4
>