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

Wed Sep 13 08:07:13 UTC 2023

[+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? Or maybe the display guys?

@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>
> *发送时间:* 2023年9月12日 17:01
> *收件人:* Pan, Xinhui <Xinhui.Pan at amd.com>; amd-gfx at lists.freedesktop.org 
> <amd-gfx at lists.freedesktop.org>
> *抄送:* Deucher, Alexander <Alexander.Deucher at amd.com>; Koenig, 
> Christian <Christian.Koenig at amd.com>; Fan, Shikang <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>
> > Sent: Friday, September 8, 2023 2:49 PM
> > To: Pan, Xinhui <Xinhui.Pan at amd.com>; amd-gfx at lists.freedesktop.org
> > Cc: Deucher, Alexander <Alexander.Deucher at amd.com>; Koenig, 
> Christian <Christian.Koenig at amd.com>; Fan, Shikang <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>
> >> ---
> >>    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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