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

[Alex Deucher]

Applied.  Thanks!

Alex

On Fri, Aug 19, 2022 at 6:07 AM Christian König
<christian.koenig@xxxxxxx> wrote:
>
> Am 19.08.22 um 11:34 schrieb 李真能:
>
> 在 2022/8/17 19:40, Christian König 写道:
>
> Am 17.08.22 um 09:31 schrieb 李真能:
>
>
> 在 2022/8/15 21:12, Christian König 写道:
>
> 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.
>
>
> Although flush_delayed_work(&rdev->fence_drv[i].lockup_work) will wait for a lockup_work to finish executing the last queueing,  but this kernel func haven't get any lock, and lockup_work will run in another kernel thread, so I think flush_delayed_work could not lead to a deadlock.
>
> Therefor if radeon_gpu_reset is called in another thread when radeon_suspend_kms is blocked on flush_delayed_work, there could not lead to a deadlock.
>
>
> Ok sounds like you didn't go what I wanted to say.
>
> The key problem is that radeon_gpu_reset() calls radeon_suspend() which in turn calls rdev->asic->suspend().
>
> And this function in turn could end up in radeon_suspend_kms() again, but I'm not 100% sure about that.
>
> Just double check the order of function called here (e.g. if radeon_suspend_kms() call radeon_suspend() or the other way around).  Apart from that your patch looks correct to me as well.
>
> radeon_gpu_reset will call radeon_suspend, but radeon_suspend will not call radeon_suspend_kms, the more detail of call flow, we can see the attachement file: radeon-suspend-reset.png.
>
> Sorry  I may have mistaken your meaning.
>
>
> Ok in this case my memory of the call flow wasn't correct any more.
>
> Feel free to add an Acked-by: Christian König <christian.koenig@xxxxxxx> to the patch.
>
> Alex should then pick it up for upstreaming.
>
> Thanks,
> Christian.
>
>
> Regards,
> Christian.
>
>
>
> 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@xxxxxxxxxx>
> ---
>   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);
>           }
>       }
>
>
>
>
>