Re: [PATCH v6] drm/imagination: Fix double call to drm_sched_entity_fini()

[Alessio Belle]

Hi Brajesh,

On Tue, 2026-06-30 at 15:33 +0530, Brajesh Gupta wrote:
> Call sequence of double call:
> pvr_context_destroy
>   pvr_context_kill_queues
>     pvr_queue_kill
>       drm_sched_entity_destroy
>         drm_sched_entity_fini // here
>   pvr_context_put
>     kref_put(..., pvr_context_release)
>       pvr_context_destroy_queues
>         pvr_queue_destroy
>           drm_sched_entity_fini // here
> 
> Call to drm_sched_entity_destroy() from pvr_context_kill_queues() calls
> drm_sched_entity_flush() + drm_sched_entity_fini().
> drm_sched_entity_flush() ensures all pending jobs are completed and
> drm_sched_entity_fini() ensures no further submission is allowed as
> per expectation from pvr_context_kill_queues(). Double call to
> drm_sched_entity_fini() is misuse of the API so keep call only in
> pvr_context_create() failure path.
> 
> Stack trace for issue with addition of refcounting for DRM entity
> stats in commit fd177135f0e6 ("drm/sched: Account entity GPU time"):

Sorry late nit: looking at other kernel dumps in commit descriptions, there
should be an empty line here.

> [  789.490527] ------------[ cut here ]------------
> [  789.490559] refcount_t: underflow; use-after-free.
> [  789.490657] WARNING: lib/refcount.c:28 at refcount_warn_saturate+0xf4/0x144, CPU#0: kworker/u16:1/440
> [  789.490695] Modules linked in: powervr drm_gpuvm drm_exec gpu_sched drm_shmem_helper xhci_plat_hcd xhci_hcd dwc3 usbcore usb_common snd_soc_simple_card snd_soc_simple_card_utils sa2ul sha512 sha256 dwc3_am62 sha1 authenc rti_wdt libsha512 at24 sch_fq_codel fuse dm_mod ipv6
> [  789.490798] CPU: 0 UID: 0 PID: 440 Comm: kworker/u16:1 Not tainted 7.0.0-rc7-02049-g5e2c0700091b #22 PREEMPT
> [  789.490809] Hardware name: Texas Instruments AM625 SK (DT)
> [  789.490815] Workqueue: powervr-sched pvr_queue_fence_release_work [powervr]
> [  789.490868] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [  789.490876] pc : refcount_warn_saturate+0xf4/0x144
> [  789.490884] lr : refcount_warn_saturate+0xf4/0x144
> [  789.490892] sp : ffff8000822cbcc0
> [  789.490895] x29: ffff8000822cbcc0 x28: 0000000000000000 x27: 0000000000000000
> [  789.490909] x26: 0000000000000000 x25: ffff800081b1e338 x24: ffff000004541405
> [  789.490922] x23: ffff000004bea950 x22: ffff00000042e400 x21: ffff000007123e30
> [  789.490935] x20: ffff000007123000 x19: ffff000007a80d50 x18: fffffffffffe7768
> [  789.490948] x17: 74736574202c6e6f x16: 697461746e656d65 x15: ffff800081b269f0
> [  789.490962] x14: 0000000000000030 x13: ffff800081b26a70 x12: 0000000000000211
> [  789.490975] x11: 00000000000000c0 x10: 0000000000000b50 x9 : ffff8000822cbb30
> [  789.490988] x8 : ffff0000014e7bb0 x7 : ffff00007725e780 x6 : 0000000372a05f49
> [  789.491001] x5 : 0000000000000000 x4 : 0000000000000001 x3 : 0000000000000010
> [  789.491013] x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff0000014e7000
> [  789.491027] Call trace:
> [  789.491032]  refcount_warn_saturate+0xf4/0x144 (P)
> [  789.491043]  drm_sched_entity_fini+0x164/0x18c [gpu_sched]
> [  789.491081]  pvr_queue_destroy+0x64/0x134 [powervr]
> [  789.491110]  pvr_context_destroy_queues+0x34/0x64 [powervr]
> [  789.491138]  pvr_context_release+0x70/0xac [powervr]
> [  789.491166]  pvr_context_put.part.0+0x5c/0x7c [powervr]
> [  789.491193]  pvr_context_put+0x14/0x24 [powervr]
> [  789.491221]  pvr_queue_fence_release_work+0x20/0x38 [powervr]
> [  789.491249]  process_one_work+0x160/0x4c4
> [  789.491264]  worker_thread+0x188/0x310
> [  789.491276]  kthread+0x130/0x13c
> [  789.491287]  ret_from_fork+0x10/0x20
> [  789.491300] ---[ end trace 0000000000000000 ]---
> 
> Fixes: eaf01ee5ba28 ("drm/imagination: Implement job submission and scheduling")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Brajesh Gupta <brajesh.gupta@xxxxxxxxxx>
> ---
> Changes in v6:
> - Fix variable name in pvr_queue.h as per v5.
> - Link to v5: https://lore.kernel.org/r/20260630-b4-sched_fix-v5-1-2a84cbf18bfe@xxxxxxxxxx
> 
> Changes in v5:
> - Update description of the issue and added stable tag.
> - Modified variable name to align with behaviour.
> - Link to v4: https://lore.kernel.org/r/20260619-b4-sched_fix-v4-1-65de5b2fd71d@xxxxxxxxxx
> 
> Changes in v4:
> - Simplify logic in v3 by pushing new flag to pvr_queue_destroy().
> - Link to v3: https://lore.kernel.org/r/20260611-b4-sched_fix-v3-1-693beb50ea01@xxxxxxxxxx
> 
> Changes in v3:
> - Fixed a typo.
> - Handled missing memory leak for RENDER_CONTEXT.
> - Link to v2: https://lore.kernel.org/r/20260611-b4-sched_fix-v2-1-17a93be86fcd@xxxxxxxxxx
> 
> Changes in v2:
> - Fixed memory leak identified in following error path handling of pvr_context_create():
> - pvr_context_create()
> -   ...
> -   err_destroy_queues:
> -     pvr_context_destroy_queues()
> -       pvr_queue_destroy()
> - Link to v1: https://lore.kernel.org/r/20260610-b4-sched_fix-v1-1-c5977a6e0b4c@xxxxxxxxxx
> ---
>  drivers/gpu/drm/imagination/pvr_context.c | 18 ++++++++++--------
>  drivers/gpu/drm/imagination/pvr_queue.c   |  6 ++++--
>  drivers/gpu/drm/imagination/pvr_queue.h   |  2 +-
>  3 files changed, 15 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/imagination/pvr_context.c b/drivers/gpu/drm/imagination/pvr_context.c
> index eba4694400b5..b6f9e078315d 100644
> --- a/drivers/gpu/drm/imagination/pvr_context.c
> +++ b/drivers/gpu/drm/imagination/pvr_context.c
> @@ -161,22 +161,24 @@ ctx_fw_data_init(void *cpu_ptr, void *priv)
>  /**
>   * pvr_context_destroy_queues() - Destroy all queues attached to a context.
>   * @ctx: Context to destroy queues on.
> + * @cleanup_queue_entity: Whether to cleanup the queue entity e.g. context
> + *                      creation failure path.

nit: Could you align the second line of this comment?

With these sorted, in v7 you can add to the end of the trailers:

Reviewed-by: Alessio Belle <alessio.belle@xxxxxxxxxx>

Thanks,
Alessio

>   *
>   * Should be called when the last reference to a context object is dropped.
>   * It releases all resources attached to the queues bound to this context.
>   */
> -static void pvr_context_destroy_queues(struct pvr_context *ctx)
> +static void pvr_context_destroy_queues(struct pvr_context *ctx, bool cleanup_queue_entity)
>  {
>  	switch (ctx->type) {
>  	case DRM_PVR_CTX_TYPE_RENDER:
> -		pvr_queue_destroy(ctx->queues.fragment);
> -		pvr_queue_destroy(ctx->queues.geometry);
> +		pvr_queue_destroy(ctx->queues.fragment, cleanup_queue_entity);
> +		pvr_queue_destroy(ctx->queues.geometry, cleanup_queue_entity);
>  		break;
>  	case DRM_PVR_CTX_TYPE_COMPUTE:
> -		pvr_queue_destroy(ctx->queues.compute);
> +		pvr_queue_destroy(ctx->queues.compute, cleanup_queue_entity);
>  		break;
>  	case DRM_PVR_CTX_TYPE_TRANSFER_FRAG:
> -		pvr_queue_destroy(ctx->queues.transfer);
> +		pvr_queue_destroy(ctx->queues.transfer, cleanup_queue_entity);
>  		break;
>  	}
>  }
> @@ -240,7 +242,7 @@ static int pvr_context_create_queues(struct pvr_context *ctx,
>  	return -EINVAL;
>  
>  err_destroy_queues:
> -	pvr_context_destroy_queues(ctx);
> +	pvr_context_destroy_queues(ctx, true);
>  	return err;
>  }
>  
> @@ -349,7 +351,7 @@ int pvr_context_create(struct pvr_file *pvr_file, struct drm_pvr_ioctl_create_co
>  	pvr_fw_object_destroy(ctx->fw_obj);
>  
>  err_destroy_queues:
> -	pvr_context_destroy_queues(ctx);
> +	pvr_context_destroy_queues(ctx, true);
>  
>  err_free_ctx_id:
>  	/*
> @@ -384,7 +386,7 @@ pvr_context_release(struct kref *ref_count)
>  	spin_unlock(&pvr_dev->ctx_list_lock);
>  
>  	xa_erase(&pvr_dev->ctx_ids, ctx->ctx_id);
> -	pvr_context_destroy_queues(ctx);
> +	pvr_context_destroy_queues(ctx, false);
>  	pvr_fw_object_destroy(ctx->fw_obj);
>  	kfree(ctx->data);
>  	pvr_vm_context_put(ctx->vm_ctx);
> diff --git a/drivers/gpu/drm/imagination/pvr_queue.c b/drivers/gpu/drm/imagination/pvr_queue.c
> index 7ed60e1c1a86..941c017399fc 100644
> --- a/drivers/gpu/drm/imagination/pvr_queue.c
> +++ b/drivers/gpu/drm/imagination/pvr_queue.c
> @@ -1439,11 +1439,12 @@ void pvr_queue_kill(struct pvr_queue *queue)
>  /**
>   * pvr_queue_destroy() - Destroy a queue.
>   * @queue: The queue to destroy.
> + * @cleanup_queue_entity: Whether to cleanup the queue entity.
>   *
>   * Cleanup the queue and free the resources attached to it. Should be
>   * called from the context release function.
>   */
> -void pvr_queue_destroy(struct pvr_queue *queue)
> +void pvr_queue_destroy(struct pvr_queue *queue, bool cleanup_queue_entity)
>  {
>  	if (!queue)
>  		return;
> @@ -1453,7 +1454,8 @@ void pvr_queue_destroy(struct pvr_queue *queue)
>  	mutex_unlock(&queue->ctx->pvr_dev->queues.lock);
>  
>  	drm_sched_fini(&queue->scheduler);
> -	drm_sched_entity_fini(&queue->entity);
> +	if (cleanup_queue_entity)
> +		drm_sched_entity_fini(&queue->entity);
>  
>  	if (WARN_ON(queue->last_queued_job_scheduled_fence))
>  		dma_fence_put(queue->last_queued_job_scheduled_fence);
> diff --git a/drivers/gpu/drm/imagination/pvr_queue.h b/drivers/gpu/drm/imagination/pvr_queue.h
> index 4aa72665ce25..149cc6d124bf 100644
> --- a/drivers/gpu/drm/imagination/pvr_queue.h
> +++ b/drivers/gpu/drm/imagination/pvr_queue.h
> @@ -158,7 +158,7 @@ struct pvr_queue *pvr_queue_create(struct pvr_context *ctx,
>  
>  void pvr_queue_kill(struct pvr_queue *queue);
>  
> -void pvr_queue_destroy(struct pvr_queue *queue);
> +void pvr_queue_destroy(struct pvr_queue *queue, bool cleanup_queue_entity);
>  
>  void pvr_queue_process(struct pvr_queue *queue);
>  
> 
> ---
> base-commit: 61de054a772a1feda6364931ab1baf9038abf1c8
> change-id: 20260610-b4-sched_fix-ac3b920f475b
> 
> Best regards,