[PATCH v2 8/8] drm/amdgpu: Prevent any job recoveries after device is unplugged.
Daniel Vetter
daniel at ffwll.ch
Wed Nov 18 07:39:24 UTC 2020
On Tue, Nov 17, 2020 at 9:07 PM Andrey Grodzovsky
<Andrey.Grodzovsky at amd.com> wrote:
>
>
> On 11/17/20 2:49 PM, Daniel Vetter wrote:
> > On Tue, Nov 17, 2020 at 02:18:49PM -0500, Andrey Grodzovsky wrote:
> >> On 11/17/20 1:52 PM, Daniel Vetter wrote:
> >>> On Tue, Nov 17, 2020 at 01:38:14PM -0500, Andrey Grodzovsky wrote:
> >>>> On 6/22/20 5:53 AM, Daniel Vetter wrote:
> >>>>> On Sun, Jun 21, 2020 at 02:03:08AM -0400, Andrey Grodzovsky wrote:
> >>>>>> No point to try recovery if device is gone, just messes up things.
> >>>>>>
> >>>>>> Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky at amd.com>
> >>>>>> ---
> >>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 16 ++++++++++++++++
> >>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_job.c | 8 ++++++++
> >>>>>> 2 files changed, 24 insertions(+)
> >>>>>>
> >>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> >>>>>> index 6932d75..5d6d3d9 100644
> >>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> >>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> >>>>>> @@ -1129,12 +1129,28 @@ static int amdgpu_pci_probe(struct pci_dev *pdev,
> >>>>>> return ret;
> >>>>>> }
> >>>>>> +static void amdgpu_cancel_all_tdr(struct amdgpu_device *adev)
> >>>>>> +{
> >>>>>> + int i;
> >>>>>> +
> >>>>>> + for (i = 0; i < AMDGPU_MAX_RINGS; ++i) {
> >>>>>> + struct amdgpu_ring *ring = adev->rings[i];
> >>>>>> +
> >>>>>> + if (!ring || !ring->sched.thread)
> >>>>>> + continue;
> >>>>>> +
> >>>>>> + cancel_delayed_work_sync(&ring->sched.work_tdr);
> >>>>>> + }
> >>>>>> +}
> >>>>> I think this is a function that's supposed to be in drm/scheduler, not
> >>>>> here. Might also just be your cleanup code being ordered wrongly, or your
> >>>>> split in one of the earlier patches not done quite right.
> >>>>> -Daniel
> >>>> This function iterates across all the schedulers per amdgpu device and accesses
> >>>> amdgpu specific structures , drm/scheduler deals with single scheduler at most
> >>>> so looks to me like this is the right place for this function
> >>> I guess we could keep track of all schedulers somewhere in a list in
> >>> struct drm_device and wrap this up. That was kinda the idea.
> >>>
> >>> Minimally I think a tiny wrapper with docs for the
> >>> cancel_delayed_work_sync(&sched->work_tdr); which explains what you must
> >>> observe to make sure there's no race.
> >>
> >> Will do
> >>
> >>
> >>> I'm not exactly sure there's no
> >>> guarantee here we won't get a new tdr work launched right afterwards at
> >>> least, so this looks a bit like a hack.
> >>
> >> Note that for any TDR work happening post amdgpu_cancel_all_tdr
> >> amdgpu_job_timedout->drm_dev_is_unplugged
> >> will return true and so it will return early. To make it water proof tight
> >> against race
> >> i can switch from drm_dev_is_unplugged to drm_dev_enter/exit
> > Hm that's confusing. You do a work_cancel_sync, so that at least looks
> > like "tdr work must not run after this point"
> >
> > If you only rely on drm_dev_enter/exit check with the tdr work, then
> > there's no need to cancel anything.
>
>
> Agree, synchronize_srcu from drm_dev_unplug should play the role
> of 'flushing' any earlier (in progress) tdr work which is
> using drm_dev_enter/exit pair. Any later arising tdr will terminate early when
> drm_dev_enter
> returns false.
Nope, anything you put into the work itself cannot close this race.
It's the schedule_work that matters here. Or I'm missing something ...
I thought that the tdr work you're cancelling here is launched by
drm/scheduler code, not by the amd callback?
-Daniel
>
> Will update.
>
> Andrey
>
>
> >
> > For race free cancel_work_sync you need:
> > 1. make sure whatever is calling schedule_work is guaranteed to no longer
> > call schedule_work.
> > 2. call cancel_work_sync
> >
> > Anything else is cargo-culted work cleanup:
> >
> > - 1. without 2. means if a work got scheduled right before it'll still be
> > a problem.
> > - 2. without 1. means a schedule_work right after makes you calling
> > cancel_work_sync pointless.
> >
> > So either both or nothing.
> > -Daniel
> >
> >> Andrey
> >>
> >>
> >>> -Daniel
> >>>
> >>>> Andrey
> >>>>
> >>>>
> >>>>>> +
> >>>>>> static void
> >>>>>> amdgpu_pci_remove(struct pci_dev *pdev)
> >>>>>> {
> >>>>>> struct drm_device *dev = pci_get_drvdata(pdev);
> >>>>>> + struct amdgpu_device *adev = dev->dev_private;
> >>>>>> drm_dev_unplug(dev);
> >>>>>> + amdgpu_cancel_all_tdr(adev);
> >>>>>> ttm_bo_unmap_virtual_address_space(&adev->mman.bdev);
> >>>>>> amdgpu_driver_unload_kms(dev);
> >>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
> >>>>>> index 4720718..87ff0c0 100644
> >>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
> >>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
> >>>>>> @@ -28,6 +28,8 @@
> >>>>>> #include "amdgpu.h"
> >>>>>> #include "amdgpu_trace.h"
> >>>>>> +#include <drm/drm_drv.h>
> >>>>>> +
> >>>>>> static void amdgpu_job_timedout(struct drm_sched_job *s_job)
> >>>>>> {
> >>>>>> struct amdgpu_ring *ring = to_amdgpu_ring(s_job->sched);
> >>>>>> @@ -37,6 +39,12 @@ static void amdgpu_job_timedout(struct drm_sched_job *s_job)
> >>>>>> memset(&ti, 0, sizeof(struct amdgpu_task_info));
> >>>>>> + if (drm_dev_is_unplugged(adev->ddev)) {
> >>>>>> + DRM_INFO("ring %s timeout, but device unplugged, skipping.\n",
> >>>>>> + s_job->sched->name);
> >>>>>> + return;
> >>>>>> + }
> >>>>>> +
> >>>>>> if (amdgpu_ring_soft_recovery(ring, job->vmid, s_job->s_fence->parent)) {
> >>>>>> DRM_ERROR("ring %s timeout, but soft recovered\n",
> >>>>>> s_job->sched->name);
> >>>>>> --
> >>>>>> 2.7.4
> >>>>>>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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