Re: [PATCH] drm/amdgpu: add missed write lock for pci detected state pci_channel_io_normal

[Andrey Grodzovsky <andrey.grodzovsky@amd.com>]

No, scheduler restart and device unlock must take place 
inamdgpu_pci_resume (see struct pci_error_handlers for the various 
states of PCI recovery). So just add a flag (probably in amdgpu_device) 
so we can remember what pci_channel_state_t we came from (unfortunately 
it's not passed to us in  amdgpu_pci_resume) and unless it's set don't 
do anything in amdgpu_pci_resume.

Andrey

On 2021-10-01 4:21 a.m., Chen, Guchun wrote:
> [Public]
>
> Hi Andrey,
>
> Do you mean to move the code of drm_sched_resubmit_jobs and drm_sched_start in amdgpu_pci_resume to amdgpu_pci_error_detected, under the case pci_channel_io_frozen?
> Then leave amdgpu_pci_resume as a null function, and in this way, we can drop the acquire/lock write lock for case of pci_channel_io_normal as well?
>
> Regards,
> Guchun
>
> -----Original Message-----
> From: Grodzovsky, Andrey <Andrey.Grodzovsky@amd.com>
> Sent: Friday, October 1, 2021 10:22 AM
> To: Chen, Guchun <Guchun.Chen@amd.com>; amd-gfx@lists.freedesktop.org; Koenig, Christian <Christian.Koenig@amd.com>; Pan, Xinhui <Xinhui.Pan@amd.com>; Deucher, Alexander <Alexander.Deucher@amd.com>
> Subject: Re: [PATCH] drm/amdgpu: add missed write lock for pci detected state pci_channel_io_normal
>
> On 2021-09-30 10:00 p.m., Guchun Chen wrote:
>
>> When a PCI error state pci_channel_io_normal is detectd, it will
>> report PCI_ERS_RESULT_CAN_RECOVER status to PCI driver, and PCI driver
>> will continue the execution of PCI resume callback report_resume by
>> pci_walk_bridge, and the callback will go into amdgpu_pci_resume
>> finally, where write lock is releasd unconditionally without acquiring
>> such lock.
>
> Good catch but, the issue is even wider in scope, what about drm_sched_resubmit_jobs and drm_sched_start called without being stopped before ? Better to put the entire scope of code in this function under flag that set only in pci_channel_io_frozen. As far as i remember we don't need to do anything in case of pci_channel_io_normal.
>
> Andrey
>
>
>> Fixes: c9a6b82f45e2("drm/amdgpu: Implement DPC recovery")
>> Signed-off-by: Guchun Chen <guchun.chen@amd.com>
>> ---
>>    drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 1 +
>>    1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>> index bb5ad2b6ca13..12f822d51de2 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>> @@ -5370,6 +5370,7 @@ pci_ers_result_t
>> amdgpu_pci_error_detected(struct pci_dev *pdev, pci_channel_sta
>>    
>>    	switch (state) {
>>    	case pci_channel_io_normal:
>> +		amdgpu_device_lock_adev(adev, NULL);
>>    		return PCI_ERS_RESULT_CAN_RECOVER;
>>    	/* Fatal error, prepare for slot reset */
>>    	case pci_channel_io_frozen: