RE: 回复: [PATCH] drm/amdgpu: Ignore first evction failure during suspend

Thu Sep 14 01:54:04 UTC 2023

[AMD Official Use Only - General]

I just make one debug patch to show busy BO’s alloc-trace when the eviction fails in suspend.
And dmesg log attached.
Looks like they are just kfd user Bos and locked by evict/restore work.
So in kfd suspend callback, it really need to flush the evict/restore work before HW fini as it do now.
That is why the first very early eviction fails and the second eviction succeed.

Thanks
xinhui
From: Pan, Xinhui
Sent: Thursday, September 14, 2023 8:02 AM
To: Koenig, Christian <Christian.Koenig at amd.com>; Kuehling, Felix <Felix.Kuehling at amd.com>; Christian König <ckoenig.leichtzumerken at gmail.com>; amd-gfx at lists.freedesktop.org; Wentland, Harry <Harry.Wentland at amd.com>
Cc: Deucher, Alexander <Alexander.Deucher at amd.com>; Fan, Shikang <Shikang.Fan at amd.com>
Subject: RE: 回复: [PATCH] drm/amdgpu: Ignore first evction failure during suspend

Chris,
I can dump these busy BOs with their alloc/free stack later today.

BTW, the two evictions and the kfd suspend are all called before hw_fini. IOW, between phase 1 and phase 2. SDMA is turned only in phase2. So current code works fine maybe.

From: Koenig, Christian <Christian.Koenig at amd.com<mailto:Christian.Koenig at amd.com>>
Sent: Wednesday, September 13, 2023 10:29 PM
To: Kuehling, Felix <Felix.Kuehling at amd.com<mailto:Felix.Kuehling at amd.com>>; Christian König <ckoenig.leichtzumerken at gmail.com<mailto:ckoenig.leichtzumerken at gmail.com>>; Pan, Xinhui <Xinhui.Pan at amd.com<mailto:Xinhui.Pan at amd.com>>; amd-gfx at lists.freedesktop.org<mailto:amd-gfx at lists.freedesktop.org>; Wentland, Harry <Harry.Wentland at amd.com<mailto:Harry.Wentland at amd.com>>
Cc: Deucher, Alexander <Alexander.Deucher at amd.com<mailto:Alexander.Deucher at amd.com>>; Fan, Shikang <Shikang.Fan at amd.com<mailto:Shikang.Fan at amd.com>>
Subject: Re: 回复: [PATCH] drm/amdgpu: Ignore first evction failure during suspend

[+Harry]
Am 13.09.23 um 15:54 schrieb Felix Kuehling:
On 2023-09-13 4:07, Christian König wrote:
[+Fleix]

Well that looks like quite a serious bug.

If I'm not completely mistaken the KFD work item tries to restore the process by moving BOs into memory even after the suspend freeze. Normally work items are frozen together with the user space processes unless explicitly marked as not freezable.

That this causes problem during the first eviction phase is just the tip of the iceberg here. If a BO is moved into invisible memory during this we wouldn't be able to get it out of that in the second phase because SDMA and hw is already turned off.

@Felix any idea how that can happen? Have you guys marked a work item / work queue as not freezable?

We don't set anything to non-freezable in KFD.

Regards,
  Felix

Or maybe the display guys?

Do you guys in the display do any delayed update in a work item which is marked as not-freezable?

Otherwise I have absolutely no idea what's going on here.

Thanks,
Christian.

@Xinhui please investigate what work item that is and where that is coming from. Something like "if (adev->in_suspend) dump_stack();" in the right place should probably do it.

Thanks,
Christian.
Am 13.09.23 um 07:13 schrieb Pan, Xinhui:

[AMD Official Use Only - General]

I notice that only user space process are frozen on my side.  kthread and workqueue  keeps running. Maybe some kernel configs are not enabled.
I made one module which just prints something like i++ with mutex lock both in workqueue and kthread. I paste some logs below.
[438619.696196] XH: 14 from workqueue
[438619.700193] XH: 15 from kthread
[438620.394335] PM: suspend entry (deep)
[438620.399619] Filesystems sync: 0.001 seconds
[438620.403887] PM: Preparing system for sleep (deep)
[438620.409299] Freezing user space processes
[438620.414862] Freezing user space processes completed (elapsed 0.001 seconds)
[438620.421881] OOM killer disabled.
[438620.425197] Freezing remaining freezable tasks
[438620.430890] Freezing remaining freezable tasks completed (elapsed 0.001 seconds)
[438620.438348] PM: Suspending system (deep)
.....
[438623.746038] PM: suspend of devices complete after 3303.137 msecs
[438623.752125] PM: start suspend of devices complete after 3309.713 msecs
[438623.758722] PM: suspend debug: Waiting for 5 second(s).
[438623.792166] XH: 22 from kthread
[438623.824140] XH: 23 from workqueue

So BOs definitely can be in use during suspend.
Even if kthread or workqueue can be stopped with one special kernel config. I think suspend can only stop the workqueue with its callback finish.
otherwise something like below makes things crazy.
LOCK BO
do something
    -> schedule or wait, anycode might sleep.  Stopped by suspend now? no, i think.
UNLOCK BO

I do tests  with  cmds below.
echo devices  > /sys/power/pm_test
echo 0  > /sys/power/pm_async
echo 1  > /sys/power/pm_print_times
echo 1 > /sys/power/pm_debug_messages
echo 1 > /sys/module/amdgpu/parameters/debug_evictions
./kfd.sh --gtest_filter=KFDEvictTest.BasicTest
pm-suspend

thanks
xinhui

________________________________
发件人: Christian König <ckoenig.leichtzumerken at gmail.com><mailto:ckoenig.leichtzumerken at gmail.com>
发送时间: 2023年9月12日 17:01
收件人: Pan, Xinhui <Xinhui.Pan at amd.com><mailto:Xinhui.Pan at amd.com>; amd-gfx at lists.freedesktop.org<mailto:amd-gfx at lists.freedesktop.org> <amd-gfx at lists.freedesktop.org><mailto:amd-gfx at lists.freedesktop.org>
抄送: Deucher, Alexander <Alexander.Deucher at amd.com><mailto:Alexander.Deucher at amd.com>; Koenig, Christian <Christian.Koenig at amd.com><mailto:Christian.Koenig at amd.com>; Fan, Shikang <Shikang.Fan at amd.com><mailto:Shikang.Fan at amd.com>
主题: Re: [PATCH] drm/amdgpu: Ignore first evction failure during suspend

When amdgpu_device_suspend() is called processes should be frozen
already. In other words KFD queues etc... should already be idle.

So when the eviction fails here we missed something previously and that
in turn can cause tons amount of problems.

So ignoring those errors is most likely not a good idea at all.

Regards,
Christian.

Am 12.09.23 um 02:21 schrieb Pan, Xinhui:
> [AMD Official Use Only - General]
>
> Oh yep, Pinned BO is moved to other LRU list, So eviction fails because of other reason.
> I will change the comments in the patch.
> The problem is eviction fails as many reasons, say, BO is locked.
> ASAIK, kfd will stop the queues and flush some evict/restore work in its suspend callback. SO the first eviction before kfd callback likely fails.
>
> -----Original Message-----
> From: Christian König <ckoenig.leichtzumerken at gmail.com><mailto:ckoenig.leichtzumerken at gmail.com>
> Sent: Friday, September 8, 2023 2:49 PM
> To: Pan, Xinhui <Xinhui.Pan at amd.com><mailto:Xinhui.Pan at amd.com>; amd-gfx at lists.freedesktop.org<mailto:amd-gfx at lists.freedesktop.org>
> Cc: Deucher, Alexander <Alexander.Deucher at amd.com><mailto:Alexander.Deucher at amd.com>; Koenig, Christian <Christian.Koenig at amd.com><mailto:Christian.Koenig at amd.com>; Fan, Shikang <Shikang.Fan at amd.com><mailto:Shikang.Fan at amd.com>
> Subject: Re: [PATCH] drm/amdgpu: Ignore first evction failure during suspend
>
> Am 08.09.23 um 05:39 schrieb xinhui pan:
>> Some BOs might be pinned. So the first eviction's failure will abort
>> the suspend sequence. These pinned BOs will be unpined afterwards
>> during suspend.
> That doesn't make much sense since pinned BOs don't cause eviction failure here.
>
> What exactly is the error code you see?
>
> Christian.
>
>> Actaully it has evicted most BOs, so that should stil work fine in
>> sriov full access mode.
>>
>> Fixes: 47ea20762bb7 ("drm/amdgpu: Add an extra evict_resource call
>> during device_suspend.")
>> Signed-off-by: xinhui pan <xinhui.pan at amd.com><mailto:xinhui.pan at amd.com>
>> ---
>>    drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 9 +++++----
>>    1 file changed, 5 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>> index 5c0e2b766026..39af526cdbbe 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>> @@ -4148,10 +4148,11 @@ int amdgpu_device_suspend(struct drm_device
>> *dev, bool fbcon)
>>
>>        adev->in_suspend = true;
>>
>> -     /* Evict the majority of BOs before grabbing the full access */
>> -     r = amdgpu_device_evict_resources(adev);
>> -     if (r)
>> -             return r;
>> +     /* Try to evict the majority of BOs before grabbing the full access
>> +      * Ignore the ret val at first place as we will unpin some BOs if any
>> +      * afterwards.
>> +      */
>> +     (void)amdgpu_device_evict_resources(adev);
>>
>>        if (amdgpu_sriov_vf(adev)) {
>>                amdgpu_virt_fini_data_exchange(adev);

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