Re: [PATCH v2 8/8] drm/amdgpu: Prevent any job recoveries after device is unplugged.

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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@xxxxxxx>
---
    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.

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

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