Re: [PATCH 3/7] drm/amdgpu: Block all job scheduling activity during DPC recovery

[Luben Tuikov <luben.tuikov@amd.com>]

On 2020-08-26 10:46, Andrey Grodzovsky wrote:
> DPC recovery involves ASIC reset just as normal GPU recovery so block
> SW GPU shcedulers and wait on all concurent GPU resets.
> 
> Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 57 +++++++++++++++++++++++++++---
>  1 file changed, 53 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> index e1bbefd..0a2130b 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> @@ -4747,6 +4747,20 @@ int amdgpu_device_baco_exit(struct drm_device *dev)
>  	return 0;
>  }
>  
> +static void amdgpu_cancel_all_tdr(struct amdgpu_device *adev)
> +{
> +	int i;
> +
> +	for (i = 0; i < AMDGPU_MAX_RINGS; ++i) {
> +		struct amdgpu_ring *ring = adev->rings[i];
> +
> +		if (!ring || !ring->sched.thread)
> +			continue;
> +
> +		cancel_delayed_work_sync(&ring->sched.work_tdr);
> +	}
> +}
> +
>  /**
>   * amdgpu_pci_error_detected - Called when a PCI error is detected.
>   * @pdev: PCI device struct
> @@ -4760,16 +4774,38 @@ pci_ers_result_t amdgpu_pci_error_detected(struct pci_dev *pdev, pci_channel_sta
>  {
>  	struct drm_device *dev = pci_get_drvdata(pdev);
>  	struct amdgpu_device *adev = drm_to_adev(dev);
> +	int i;
>  
>  	DRM_INFO("PCI error: detected callback, state(%d)!!\n", state);
>  
>  	switch (state) {
>  	case pci_channel_io_normal:
>  		return PCI_ERS_RESULT_CAN_RECOVER;
> -	case pci_channel_io_frozen: {
> -		/* Fatal error, prepare for slot reset */
> +	case pci_channel_io_frozen: { /* Fatal error, prepare for slot reset */
> +
> +		/*
> +		 * Cancel and wait for all TDRs in progress if failing to
> +		 * set  adev->in_gpu_reset in amdgpu_device_lock_adev
> +		 *
> +		 * Locking adev->reset_sem will perevent any external access
> +		 * to GPU during PCI error recovery
> +		 */
> +		while (!amdgpu_device_lock_adev(adev, NULL))
> +			amdgpu_cancel_all_tdr(adev);

Is it possible for this to hang forever? It eventually
resolves to __cancel_work_timer() in kernel/workqueue.c
which provides no timeout.

If you cannot guarantee the TDRs to return back, then
you'd need a timeout here.

Regards,
Luben

> +
> +		/*
> +		 * Block any work scheduling as we do for regualr GPU reset
> +		 * for the duration of the recoveryq
> +		 */
> +		for (i = 0; i < AMDGPU_MAX_RINGS; ++i) {
> +			struct amdgpu_ring *ring = adev->rings[i];
> +
> +			if (!ring || !ring->sched.thread)
> +				continue;
> +
> +			drm_sched_stop(&ring->sched, NULL);
> +		}
>  
> -		amdgpu_device_lock_adev(adev);
>  		return PCI_ERS_RESULT_NEED_RESET;
>  	}
>  	case pci_channel_io_perm_failure:
> @@ -4902,8 +4938,21 @@ void amdgpu_pci_resume(struct pci_dev *pdev)
>  {
>  	struct drm_device *dev = pci_get_drvdata(pdev);
>  	struct amdgpu_device *adev = drm_to_adev(dev);
> +	int i;
>  
> -	amdgpu_device_unlock_adev(adev);
>  
>  	DRM_INFO("PCI error: resume callback!!\n");
> +
> +	for (i = 0; i < AMDGPU_MAX_RINGS; ++i) {
> +		struct amdgpu_ring *ring = adev->rings[i];
> +
> +		if (!ring || !ring->sched.thread)
> +			continue;
> +
> +
> +		drm_sched_resubmit_jobs(&ring->sched);
> +		drm_sched_start(&ring->sched, true);
> +	}
> +
> +	amdgpu_device_unlock_adev(adev);
>  }
> 

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