Re: [PATCH] drm/radeon: add a force flush to delay work when radeon

["Christian König" <christian.koenig@amd.com>]

Am 15.08.22 um 09:34 schrieb 李真能:
>
> 在 2022/8/12 18:55, Christian König 写道:
>> Am 11.08.22 um 09:25 schrieb Zhenneng Li:
>>> Although radeon card fence and wait for gpu to finish processing 
>>> current batch rings,
>>> there is still a corner case that radeon lockup work queue may not 
>>> be fully flushed,
>>> and meanwhile the radeon_suspend_kms() function has called 
>>> pci_set_power_state() to
>>> put device in D3hot state.
>>
>> If I'm not completely mistaken the reset worker uses the 
>> suspend/resume functionality as well to get the hardware into a 
>> working state again.
>>
>> So if I'm not completely mistaken this here would lead to a deadlock, 
>> please double check that.
>
> We have tested many times, there are no deadlock.

Testing doesn't tells you anything, you need to audit the call paths.

> In which situation, there would lead to a deadlock?

GPU resets.

Regards,
Christian.

>
>>
>> Regards,
>> Christian.
>>
>>> Per PCI spec rev 4.0 on 5.3.1.4.1 D3hot State.
>>>> Configuration and Message requests are the only TLPs accepted by a 
>>>> Function in
>>>> the D3hot state. All other received Requests must be handled as 
>>>> Unsupported Requests,
>>>> and all received Completions may optionally be handled as 
>>>> Unexpected Completions.
>>> This issue will happen in following logs:
>>> Unable to handle kernel paging request at virtual address 
>>> 00008800e0008010
>>> CPU 0 kworker/0:3(131): Oops 0
>>> pc = [<ffffffff811bea5c>]  ra = [<ffffffff81240844>]  ps = 0000 
>>> Tainted: G        W
>>> pc is at si_gpu_check_soft_reset+0x3c/0x240
>>> ra is at si_dma_is_lockup+0x34/0xd0
>>> v0 = 0000000000000000  t0 = fff08800e0008010  t1 = 0000000000010000
>>> t2 = 0000000000008010  t3 = fff00007e3c00000  t4 = fff00007e3c00258
>>> t5 = 000000000000ffff  t6 = 0000000000000001  t7 = fff00007ef078000
>>> s0 = fff00007e3c016e8  s1 = fff00007e3c00000  s2 = fff00007e3c00018
>>> s3 = fff00007e3c00000  s4 = fff00007fff59d80  s5 = 0000000000000000
>>> s6 = fff00007ef07bd98
>>> a0 = fff00007e3c00000  a1 = fff00007e3c016e8  a2 = 0000000000000008
>>> a3 = 0000000000000001  a4 = 8f5c28f5c28f5c29  a5 = ffffffff810f4338
>>> t8 = 0000000000000275  t9 = ffffffff809b66f8  t10 = ff6769c5d964b800
>>> t11= 000000000000b886  pv = ffffffff811bea20  at = 0000000000000000
>>> gp = ffffffff81d89690  sp = 00000000aa814126
>>> Disabling lock debugging due to kernel taint
>>> Trace:
>>> [<ffffffff81240844>] si_dma_is_lockup+0x34/0xd0
>>> [<ffffffff81119610>] radeon_fence_check_lockup+0xd0/0x290
>>> [<ffffffff80977010>] process_one_work+0x280/0x550
>>> [<ffffffff80977350>] worker_thread+0x70/0x7c0
>>> [<ffffffff80977410>] worker_thread+0x130/0x7c0
>>> [<ffffffff80982040>] kthread+0x200/0x210
>>> [<ffffffff809772e0>] worker_thread+0x0/0x7c0
>>> [<ffffffff80981f8c>] kthread+0x14c/0x210
>>> [<ffffffff80911658>] ret_from_kernel_thread+0x18/0x20
>>> [<ffffffff80981e40>] kthread+0x0/0x210
>>>   Code: ad3e0008  43f0074a  ad7e0018  ad9e0020  8c3001e8 40230101
>>>   <88210000> 4821ed21
>>> So force lockup work queue flush to fix this problem.
>>>
>>> Signed-off-by: Zhenneng Li <lizhenneng@kylinos.cn>
>>> ---
>>>   drivers/gpu/drm/radeon/radeon_device.c | 3 +++
>>>   1 file changed, 3 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/radeon/radeon_device.c 
>>> b/drivers/gpu/drm/radeon/radeon_device.c
>>> index 15692cb241fc..e608ca26780a 100644
>>> --- a/drivers/gpu/drm/radeon/radeon_device.c
>>> +++ b/drivers/gpu/drm/radeon/radeon_device.c
>>> @@ -1604,6 +1604,9 @@ int radeon_suspend_kms(struct drm_device *dev, 
>>> bool suspend,
>>>           if (r) {
>>>               /* delay GPU reset to resume */
>>>               radeon_fence_driver_force_completion(rdev, i);
>>> +        } else {
>>> +            /* finish executing delayed work */
>>> + flush_delayed_work(&rdev->fence_drv[i].lockup_work);
>>>           }
>>>       }
>>