[Freedreno] [PATCH v2 1/2] drm/msm: Fix premature purging of BO
Akhil P Oommen
akhilpo at codeaurora.org
Wed Sep 23 18:28:14 UTC 2020
On 9/23/2020 8:20 PM, Jordan Crouse wrote:
> On Tue, Sep 22, 2020 at 08:25:26PM +0530, Akhil P Oommen wrote:
>> In the case where we have a back-to-back submission that shares the same
>> BO, this BO will be prematurely moved to inactive_list while retiring the
>> first submit. But it will be still part of the second submit which is
>> being processed by the GPU. Now, if the shrinker happens to be triggered at
>> this point, it will result in a premature purging of this BO.
>>
>> To fix this, we need to refcount BO while doing submit and retire. Then,
>> it should be moved to inactive list when this refcount becomes 0.
>>
>> Signed-off-by: Akhil P Oommen <akhilpo at codeaurora.org>
>> ---
>> Changes in v2:
>> 1. Keep Active List around
>> 2. Put back the deleted WARN_ON
>>
>> drivers/gpu/drm/msm/msm_drv.h | 5 ++---
>> drivers/gpu/drm/msm/msm_gem.c | 32 ++++++++++++++++----------------
>> drivers/gpu/drm/msm/msm_gem.h | 4 +++-
>> drivers/gpu/drm/msm/msm_gpu.c | 11 +++++++----
>> 4 files changed, 28 insertions(+), 24 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
>> index 3193274..28e3c8d 100644
>> --- a/drivers/gpu/drm/msm/msm_drv.h
>> +++ b/drivers/gpu/drm/msm/msm_drv.h
>> @@ -309,9 +309,8 @@ void msm_gem_put_vaddr(struct drm_gem_object *obj);
>> int msm_gem_madvise(struct drm_gem_object *obj, unsigned madv);
>> int msm_gem_sync_object(struct drm_gem_object *obj,
>> struct msm_fence_context *fctx, bool exclusive);
>> -void msm_gem_move_to_active(struct drm_gem_object *obj,
>> - struct msm_gpu *gpu, bool exclusive, struct dma_fence *fence);
>> -void msm_gem_move_to_inactive(struct drm_gem_object *obj);
>> +void msm_gem_active_get(struct drm_gem_object *obj, struct msm_gpu *gpu);
>> +void msm_gem_active_put(struct drm_gem_object *obj);
>> int msm_gem_cpu_prep(struct drm_gem_object *obj, uint32_t op, ktime_t *timeout);
>> int msm_gem_cpu_fini(struct drm_gem_object *obj);
>> void msm_gem_free_object(struct drm_gem_object *obj);
>> diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
>> index 76a6c52..14e14ca 100644
>> --- a/drivers/gpu/drm/msm/msm_gem.c
>> +++ b/drivers/gpu/drm/msm/msm_gem.c
>> @@ -743,31 +743,31 @@ int msm_gem_sync_object(struct drm_gem_object *obj,
>> return 0;
>> }
>>
>> -void msm_gem_move_to_active(struct drm_gem_object *obj,
>> - struct msm_gpu *gpu, bool exclusive, struct dma_fence *fence)
>> +void msm_gem_active_get(struct drm_gem_object *obj, struct msm_gpu *gpu)
>> {
>> struct msm_gem_object *msm_obj = to_msm_bo(obj);
>> + WARN_ON(!mutex_is_locked(&obj->dev->struct_mutex));
>> WARN_ON(msm_obj->madv != MSM_MADV_WILLNEED);
>> - msm_obj->gpu = gpu;
>> - if (exclusive)
>> - dma_resv_add_excl_fence(obj->resv, fence);
>> - else
>> - dma_resv_add_shared_fence(obj->resv, fence);
>> - list_del_init(&msm_obj->mm_list);
>> - list_add_tail(&msm_obj->mm_list, &gpu->active_list);
>> +
>> + if (!atomic_fetch_inc(&msm_obj->active_count)) {
>> + msm_obj->gpu = gpu;
>> + list_del_init(&msm_obj->mm_list);
>> + list_add_tail(&msm_obj->mm_list, &gpu->active_list);
>> + }
>
> I'm not sure if all the renaming and reorganization are really needed here -
> this is the meat of the change and it would have fit in reasonably well with the
> existing function design.
This happened due to the way I implemented the v1 patch. In the
hindsight, I think you are right.
Akhil.
>
>> }
>>
>> -void msm_gem_move_to_inactive(struct drm_gem_object *obj)
>> +void msm_gem_active_put(struct drm_gem_object *obj)
>> {
>> - struct drm_device *dev = obj->dev;
>> - struct msm_drm_private *priv = dev->dev_private;
>> struct msm_gem_object *msm_obj = to_msm_bo(obj);
>> + struct msm_drm_private *priv = obj->dev->dev_private;
>>
>> - WARN_ON(!mutex_is_locked(&dev->struct_mutex));
>> + WARN_ON(!mutex_is_locked(&obj->dev->struct_mutex));
>>
>> - msm_obj->gpu = NULL;
>> - list_del_init(&msm_obj->mm_list);
>> - list_add_tail(&msm_obj->mm_list, &priv->inactive_list);
>> + if (!atomic_dec_return(&msm_obj->active_count)) {
>> + msm_obj->gpu = NULL;
>> + list_del_init(&msm_obj->mm_list);
>> + list_add_tail(&msm_obj->mm_list, &priv->inactive_list);
>> + }
>
> Same.
>
> Jordan
>> }
>>
>> int msm_gem_cpu_prep(struct drm_gem_object *obj, uint32_t op, ktime_t *timeout)
>> diff --git a/drivers/gpu/drm/msm/msm_gem.h b/drivers/gpu/drm/msm/msm_gem.h
>> index 7b1c7a5..a1bf741 100644
>> --- a/drivers/gpu/drm/msm/msm_gem.h
>> +++ b/drivers/gpu/drm/msm/msm_gem.h
>> @@ -88,12 +88,14 @@ struct msm_gem_object {
>> struct mutex lock; /* Protects resources associated with bo */
>>
>> char name[32]; /* Identifier to print for the debugfs files */
>> +
>> + atomic_t active_count;
>> };
>> #define to_msm_bo(x) container_of(x, struct msm_gem_object, base)
>>
>> static inline bool is_active(struct msm_gem_object *msm_obj)
>> {
>> - return msm_obj->gpu != NULL;
>> + return atomic_read(&msm_obj->active_count);
>> }
>>
>> static inline bool is_purgeable(struct msm_gem_object *msm_obj)
>> diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
>> index 29c8d73c..55d1648 100644
>> --- a/drivers/gpu/drm/msm/msm_gpu.c
>> +++ b/drivers/gpu/drm/msm/msm_gpu.c
>> @@ -698,8 +698,8 @@ static void retire_submit(struct msm_gpu *gpu, struct msm_ringbuffer *ring,
>>
>> for (i = 0; i < submit->nr_bos; i++) {
>> struct msm_gem_object *msm_obj = submit->bos[i].obj;
>> - /* move to inactive: */
>> - msm_gem_move_to_inactive(&msm_obj->base);
>> +
>> + msm_gem_active_put(&msm_obj->base);
>> msm_gem_unpin_iova(&msm_obj->base, submit->aspace);
>> drm_gem_object_put_locked(&msm_obj->base);
>> }
>> @@ -774,6 +774,7 @@ void msm_gpu_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit)
>>
>> for (i = 0; i < submit->nr_bos; i++) {
>> struct msm_gem_object *msm_obj = submit->bos[i].obj;
>> + struct drm_gem_object *drm_obj = &msm_obj->base;
>> uint64_t iova;
>>
>> /* can't happen yet.. but when we add 2d support we'll have
>> @@ -786,9 +787,11 @@ void msm_gpu_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit)
>> msm_gem_get_and_pin_iova(&msm_obj->base, submit->aspace, &iova);
>>
>> if (submit->bos[i].flags & MSM_SUBMIT_BO_WRITE)
>> - msm_gem_move_to_active(&msm_obj->base, gpu, true, submit->fence);
>> + dma_resv_add_excl_fence(drm_obj->resv, submit->fence);
>> else if (submit->bos[i].flags & MSM_SUBMIT_BO_READ)
>> - msm_gem_move_to_active(&msm_obj->base, gpu, false, submit->fence);
>> + dma_resv_add_shared_fence(drm_obj->resv, submit->fence);
>> +
>> + msm_gem_active_get(drm_obj, gpu);
>> }
>>
>> gpu->funcs->submit(gpu, submit);
>> --
>> 2.7.4
>>
>
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