[PATCH 5/5] drm/amd/sched: signal and free remaining fences in amd_sched_entity_fini
Nicolai Hähnle
nicolai.haehnle at amd.com
Mon Oct 9 11:27:51 UTC 2017
On 09.10.2017 13:12, Christian König wrote:
>>
>>> Nicolai, how hard would it be to handle ENODEV as failure for all
>>> currently existing contexts?
>>
>> Impossible? "All currently existing contexts" is not a well-defined
>> concept when multiple drivers co-exist in the same process.
>
> Ok, let me refine the question: I assume there are resources "shared"
> between contexts like binary shader code for example which needs to be
> reuploaded when VRAM is lost.
>
> How hard would it be to handle that correctly?
Okay, that makes more sense :)
With the current interface it's still pretty difficult, but if we could
get a new per-device query ioctl which returns a "VRAM loss counter", it
would be reasonably straight-forward.
>> And what would be the purpose of this? If it's to support VRAM loss,
>> having a per-context VRAM loss counter would enable each context to
>> signal ECANCELED separately.
>
> I thought of that on top of the -ENODEV handling.
>
> In other words when we see -ENODEV we call an IOCTL to let the kernel
> know we noticed that something is wrong and then reinit all shared
> resources in userspace.
>
> All existing context will still see -ECANCELED when we drop their
> command submission, but new contexts would at least not cause a new
> lockup immediately because their shader binaries are corrupted.
I don't think we need -ENODEV for this. We just need -ECANCELED to be
returned when a submission is rejected due to reset (hang or VRAM loss).
Mesa would keep a shadow of the VRAM loss counter in pipe_screen and
pipe_context, and query the kernel's counter when it encounters
-ECANCELED. Each context would then know to drop the CS it's built up so
far and restart based on comparing the VRAM loss counter of pipe_screen
to that of pipe_context, and similarly we could keep a copy of the VRAM
loss counter for important buffer objects like shader binaries,
descriptors, etc.
This seems more robust to me than relying only on an ENODEV. We'd most
likely keep some kind of VRAM loss counter in Mesa *anyway* (we don't
maintain a list of all shaders, for example, and we can't nuke important
per-context across threads), and synthesizing such a counter from
ENODEVs is not particularly robust (what if multiple ENODEVs occur for
the same loss event?).
BTW, I still don't like ENODEV. It seems more like the kind of error
code you'd return with hot-pluggable GPUs where the device can
physically disappear...
Cheers,
Nicolai
>
> Regards,
> Christian.
>
> Am 09.10.2017 um 13:04 schrieb Nicolai Hähnle:
>> On 09.10.2017 12:59, Christian König wrote:
>>> Nicolai, how hard would it be to handle ENODEV as failure for all
>>> currently existing contexts?
>>
>> Impossible? "All currently existing contexts" is not a well-defined
>> concept when multiple drivers co-exist in the same process.
>>
>> And what would be the purpose of this? If it's to support VRAM loss,
>> having a per-context VRAM loss counter would enable each context to
>> signal ECANCELED separately.
>>
>> Cheers,
>> Nicolai
>>
>>
>>>
>>> Monk, would it be ok with you when we return ENODEV only for existing
>>> context when VRAM is lost and/or we have a strict mode GPU reset?
>>> E.g. newly created contexts would continue work as they should.
>>>
>>> Regards,
>>> Christian.
>>>
>>> Am 09.10.2017 um 12:49 schrieb Nicolai Hähnle:
>>>> Hi Monk,
>>>>
>>>> Yes, you're right, we're only using ECANCELED internally. But as a
>>>> consequence, Mesa would already handle a kernel error of ECANCELED
>>>> on context loss correctly :)
>>>>
>>>> Cheers,
>>>> Nicolai
>>>>
>>>> On 09.10.2017 12:35, Liu, Monk wrote:
>>>>> Hi Christian
>>>>>
>>>>> You reject some of my patches that returns -ENODEV, with the cause
>>>>> that MESA doesn't do the handling on -ENODEV
>>>>>
>>>>> But if Nicolai can confirm that MESA do have a handling on
>>>>> -ECANCELED, then we need to overall align our error code, on detail
>>>>> below IOCTL can return error code:
>>>>>
>>>>> Amdgpu_cs_ioctl
>>>>> Amdgpu_cs_wait_ioctl
>>>>> Amdgpu_cs_wait_fences_ioctl
>>>>> Amdgpu_info_ioctl
>>>>>
>>>>>
>>>>> My patches is:
>>>>> return -ENODEV on cs_ioctl if the context is detected guilty,
>>>>> also return -ENODEV on cs_wait|cs_wait_fences if the fence is
>>>>> signaled but with error -ETIME,
>>>>> also return -ENODEV on info_ioctl so UMD can query if gpu reset
>>>>> happened after the process created (because for strict mode we
>>>>> block process instead of context)
>>>>>
>>>>>
>>>>> according to Nicolai:
>>>>>
>>>>> amdgpu_cs_ioctl *can* return -ECANCELED, but to be frankly
>>>>> speaking, kernel part doesn't have any place with "-ECANCELED" so
>>>>> this solution on MESA side doesn't align with *current* amdgpu driver,
>>>>> which only return 0 on success or -EINVALID on other error but
>>>>> definitely no "-ECANCELED" error code,
>>>>>
>>>>> so if we talking about community rules we shouldn't let MESA handle
>>>>> -ECANCELED , we should have a unified error code
>>>>>
>>>>> + Marek
>>>>>
>>>>> BR Monk
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> -----Original Message-----
>>>>> From: Haehnle, Nicolai
>>>>> Sent: 2017年10月9日 18:14
>>>>> To: Koenig, Christian <Christian.Koenig at amd.com>; Liu, Monk
>>>>> <Monk.Liu at amd.com>; Nicolai Hähnle <nhaehnle at gmail.com>;
>>>>> amd-gfx at lists.freedesktop.org
>>>>> Subject: Re: [PATCH 5/5] drm/amd/sched: signal and free remaining
>>>>> fences in amd_sched_entity_fini
>>>>>
>>>>> On 09.10.2017 10:02, Christian König wrote:
>>>>>>> For gpu reset patches (already submitted to pub) I would make kernel
>>>>>>> return -ENODEV if the waiting fence (in cs_wait or wait_fences
>>>>>>> IOCTL)
>>>>>>> founded as error, that way UMD would run into robust extension path
>>>>>>> and considering the GPU hang occurred,
>>>>>> Well that is only closed source behavior which is completely
>>>>>> irrelevant for upstream development.
>>>>>>
>>>>>> As far as I know we haven't pushed the change to return -ENODEV
>>>>>> upstream.
>>>>>
>>>>> FWIW, radeonsi currently expects -ECANCELED on CS submissions and
>>>>> treats those as context lost. Perhaps we could use the same error
>>>>> on fences?
>>>>> That makes more sense to me than -ENODEV.
>>>>>
>>>>> Cheers,
>>>>> Nicolai
>>>>>
>>>>>>
>>>>>> Regards,
>>>>>> Christian.
>>>>>>
>>>>>> Am 09.10.2017 um 08:42 schrieb Liu, Monk:
>>>>>>> Christian
>>>>>>>
>>>>>>>> It would be really nice to have an error code set on
>>>>>>>> s_fence->finished before it is signaled, use dma_fence_set_error()
>>>>>>>> for this.
>>>>>>> For gpu reset patches (already submitted to pub) I would make kernel
>>>>>>> return -ENODEV if the waiting fence (in cs_wait or wait_fences
>>>>>>> IOCTL)
>>>>>>> founded as error, that way UMD would run into robust extension path
>>>>>>> and considering the GPU hang occurred,
>>>>>>>
>>>>>>> Don't know if this is expected for the case of normal process being
>>>>>>> killed or crashed like Nicolai hit ... since there is no gpu hang
>>>>>>> hit
>>>>>>>
>>>>>>>
>>>>>>> BR Monk
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> -----Original Message-----
>>>>>>> From: amd-gfx [mailto:amd-gfx-bounces at lists.freedesktop.org] On
>>>>>>> Behalf Of Christian K?nig
>>>>>>> Sent: 2017年9月28日 23:01
>>>>>>> To: Nicolai Hähnle <nhaehnle at gmail.com>;
>>>>>>> amd-gfx at lists.freedesktop.org
>>>>>>> Cc: Haehnle, Nicolai <Nicolai.Haehnle at amd.com>
>>>>>>> Subject: Re: [PATCH 5/5] drm/amd/sched: signal and free remaining
>>>>>>> fences in amd_sched_entity_fini
>>>>>>>
>>>>>>> Am 28.09.2017 um 16:55 schrieb Nicolai Hähnle:
>>>>>>>> From: Nicolai Hähnle <nicolai.haehnle at amd.com>
>>>>>>>>
>>>>>>>> Highly concurrent Piglit runs can trigger a race condition where a
>>>>>>>> pending SDMA job on a buffer object is never executed because the
>>>>>>>> corresponding process is killed (perhaps due to a crash). Since the
>>>>>>>> job's fences were never signaled, the buffer object was effectively
>>>>>>>> leaked. Worse, the buffer was stuck wherever it happened to be at
>>>>>>>> the time, possibly in VRAM.
>>>>>>>>
>>>>>>>> The symptom was user space processes stuck in interruptible waits
>>>>>>>> with kernel stacks like:
>>>>>>>>
>>>>>>>> [<ffffffffbc5e6722>] dma_fence_default_wait+0x112/0x250
>>>>>>>> [<ffffffffbc5e6399>] dma_fence_wait_timeout+0x39/0xf0
>>>>>>>> [<ffffffffbc5e82d2>]
>>>>>>>> reservation_object_wait_timeout_rcu+0x1c2/0x300
>>>>>>>> [<ffffffffc03ce56f>]
>>>>>>>> ttm_bo_cleanup_refs_and_unlock+0xff/0x1a0
>>>>>>>> [ttm]
>>>>>>>> [<ffffffffc03cf1ea>] ttm_mem_evict_first+0xba/0x1a0 [ttm]
>>>>>>>> [<ffffffffc03cf611>] ttm_bo_mem_space+0x341/0x4c0 [ttm]
>>>>>>>> [<ffffffffc03cfc54>] ttm_bo_validate+0xd4/0x150 [ttm]
>>>>>>>> [<ffffffffc03cffbd>] ttm_bo_init_reserved+0x2ed/0x420 [ttm]
>>>>>>>> [<ffffffffc042f523>] amdgpu_bo_create_restricted+0x1f3/0x470
>>>>>>>> [amdgpu]
>>>>>>>> [<ffffffffc042f9fa>] amdgpu_bo_create+0xda/0x220 [amdgpu]
>>>>>>>> [<ffffffffc04349ea>] amdgpu_gem_object_create+0xaa/0x140
>>>>>>>> [amdgpu]
>>>>>>>> [<ffffffffc0434f97>] amdgpu_gem_create_ioctl+0x97/0x120
>>>>>>>> [amdgpu]
>>>>>>>> [<ffffffffc037ddba>] drm_ioctl+0x1fa/0x480 [drm]
>>>>>>>> [<ffffffffc041904f>] amdgpu_drm_ioctl+0x4f/0x90 [amdgpu]
>>>>>>>> [<ffffffffbc23db33>] do_vfs_ioctl+0xa3/0x5f0
>>>>>>>> [<ffffffffbc23e0f9>] SyS_ioctl+0x79/0x90
>>>>>>>> [<ffffffffbc864ffb>] entry_SYSCALL_64_fastpath+0x1e/0xad
>>>>>>>> [<ffffffffffffffff>] 0xffffffffffffffff
>>>>>>>>
>>>>>>>> Signed-off-by: Nicolai Hähnle <nicolai.haehnle at amd.com>
>>>>>>>> Acked-by: Christian König <christian.koenig at amd.com>
>>>>>>>> ---
>>>>>>>> drivers/gpu/drm/amd/scheduler/gpu_scheduler.c | 7 ++++++-
>>>>>>>> 1 file changed, 6 insertions(+), 1 deletion(-)
>>>>>>>>
>>>>>>>> diff --git a/drivers/gpu/drm/amd/scheduler/gpu_scheduler.c
>>>>>>>> b/drivers/gpu/drm/amd/scheduler/gpu_scheduler.c
>>>>>>>> index 54eb77cffd9b..32a99e980d78 100644
>>>>>>>> --- a/drivers/gpu/drm/amd/scheduler/gpu_scheduler.c
>>>>>>>> +++ b/drivers/gpu/drm/amd/scheduler/gpu_scheduler.c
>>>>>>>> @@ -220,22 +220,27 @@ void amd_sched_entity_fini(struct
>>>>>>>> amd_gpu_scheduler *sched,
>>>>>>>> amd_sched_entity_is_idle(entity));
>>>>>>>> amd_sched_rq_remove_entity(rq, entity);
>>>>>>>> if (r) {
>>>>>>>> struct amd_sched_job *job;
>>>>>>>> /* Park the kernel for a moment to make sure it isn't
>>>>>>>> processing
>>>>>>>> * our enity.
>>>>>>>> */
>>>>>>>> kthread_park(sched->thread);
>>>>>>>> kthread_unpark(sched->thread);
>>>>>>>> - while (kfifo_out(&entity->job_queue, &job, sizeof(job)))
>>>>>>>> + while (kfifo_out(&entity->job_queue, &job, sizeof(job))) {
>>>>>>>> + struct amd_sched_fence *s_fence = job->s_fence;
>>>>>>>> + amd_sched_fence_scheduled(s_fence);
>>>>>>> It would be really nice to have an error code set on
>>>>>>> s_fence->finished before it is signaled, use
>>>>>>> dma_fence_set_error() for this.
>>>>>>>
>>>>>>> Additional to that it would be nice to note in the subject line that
>>>>>>> this is a rather important bug fix.
>>>>>>>
>>>>>>> With that fixed the whole series is Reviewed-by: Christian König
>>>>>>> <christian.koenig at amd.com>.
>>>>>>>
>>>>>>> Regards,
>>>>>>> Christian.
>>>>>>>
>>>>>>>> + amd_sched_fence_finished(s_fence);
>>>>>>>> + dma_fence_put(&s_fence->finished);
>>>>>>>> sched->ops->free_job(job);
>>>>>>>> + }
>>>>>>>> }
>>>>>>>> kfifo_free(&entity->job_queue);
>>>>>>>> }
>>>>>>>> static void amd_sched_entity_wakeup(struct dma_fence *f, struct
>>>>>>>> dma_fence_cb *cb)
>>>>>>>> {
>>>>>>>> struct amd_sched_entity *entity =
>>>>>>>> container_of(cb, struct amd_sched_entity, cb);
>>>>>>>> entity->dependency = NULL;
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> amd-gfx mailing list
>>>>>>> amd-gfx at lists.freedesktop.org
>>>>>>> https://lists.freedesktop.org/mailman/listinfo/amd-gfx
>>>>>>> _______________________________________________
>>>>>>> amd-gfx mailing list
>>>>>>> amd-gfx at lists.freedesktop.org
>>>>>>> https://lists.freedesktop.org/mailman/listinfo/amd-gfx
>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>
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