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From: Daniel Vetter <daniel@ffwll.ch>
To: "Christian König" <christian.koenig@amd.com>
Cc: "DRI Development" <dri-devel@lists.freedesktop.org>,
	"Steven Price" <steven.price@arm.com>,
	"Daniel Vetter" <daniel.vetter@intel.com>,
	"Lucas Stach" <l.stach@pengutronix.de>,
	"Russell King" <linux+etnaviv@armlinux.org.uk>,
	"Christian Gmeiner" <christian.gmeiner@gmail.com>,
	"Qiang Yu" <yuq825@gmail.com>, "Rob Herring" <robh@kernel.org>,
	"Tomeu Vizoso" <tomeu.vizoso@collabora.com>,
	"Alyssa Rosenzweig" <alyssa.rosenzweig@collabora.com>,
	"David Airlie" <airlied@linux.ie>,
	"Sumit Semwal" <sumit.semwal@linaro.org>,
	"Masahiro Yamada" <masahiroy@kernel.org>,
	"Kees Cook" <keescook@chromium.org>,
	"Adam Borowski" <kilobyte@angband.pl>,
	"Nick Terrell" <terrelln@fb.com>,
	"Mauro Carvalho Chehab" <mchehab+huawei@kernel.org>,
	"Paul Menzel" <pmenzel@molgen.mpg.de>,
	"Sami Tolvanen" <samitolvanen@google.com>,
	"Viresh Kumar" <viresh.kumar@linaro.org>,
	"Alex Deucher" <alexander.deucher@amd.com>,
	"Dave Airlie" <airlied@redhat.com>,
	"Nirmoy Das" <nirmoy.das@amd.com>,
	"Deepak R Varma" <mh12gx2825@gmail.com>,
	"Lee Jones" <lee.jones@linaro.org>,
	"Kevin Wang" <kevin1.wang@amd.com>,
	"Chen Li" <chenli@uniontech.com>,
	"Luben Tuikov" <luben.tuikov@amd.com>,
	"Marek Olšák" <marek.olsak@amd.com>,
	"Dennis Li" <Dennis.Li@amd.com>,
	"Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>,
	"Andrey Grodzovsky" <andrey.grodzovsky@amd.com>,
	"Sonny Jiang" <sonny.jiang@amd.com>,
	"Boris Brezillon" <boris.brezillon@collabora.com>,
	"Tian Tao" <tiantao6@hisilicon.com>,
	"Jack Zhang" <Jack.Zhang1@amd.com>,
	"The etnaviv authors" <etnaviv@lists.freedesktop.org>,
	lima@lists.freedesktop.org,
	"open list:DMA BUFFER SHARING FRAMEWORK"
	<linux-media@vger.kernel.org>,
	"moderated list:DMA BUFFER SHARING FRAMEWORK"
	<linaro-mm-sig@lists.linaro.org>, "Emma Anholt" <emma@anholt.net>
Subject: Re: [PATCH v2 01/11] drm/sched: Split drm_sched_job_init
Date: Thu, 8 Jul 2021 13:20:32 +0200	[thread overview]
Message-ID: <CAKMK7uE4H2nsAYSAQGB0R7YTHUFvfNmshE2Bqy0uSdHomPxo=A@mail.gmail.com> (raw)
In-Reply-To: <700b6419-4d3c-9cc8-f8bd-0d7d134df546@amd.com>

On Thu, Jul 8, 2021 at 12:54 PM Christian König
<christian.koenig@amd.com> wrote:
>
> Am 08.07.21 um 12:02 schrieb Daniel Vetter:
> > On Thu, Jul 08, 2021 at 09:53:00AM +0200, Christian König wrote:
> >> Am 08.07.21 um 09:19 schrieb Daniel Vetter:
> >>> On Thu, Jul 8, 2021 at 9:09 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> >>>> On Thu, Jul 8, 2021 at 8:56 AM Christian König <christian.koenig@amd.com> wrote:
> >>>>> Am 07.07.21 um 18:32 schrieb Daniel Vetter:
> >>>>>> On Wed, Jul 7, 2021 at 2:58 PM Christian König <christian.koenig@amd.com> wrote:
> >>>>>>> Am 07.07.21 um 14:13 schrieb Daniel Vetter:
> >>>>>>>> On Wed, Jul 7, 2021 at 1:57 PM Christian König <christian.koenig@amd.com> wrote:
> >>>>>>>>> Am 07.07.21 um 13:14 schrieb Daniel Vetter:
> >>>>>>>>>> On Wed, Jul 7, 2021 at 11:30 AM Christian König
> >>>>>>>>>> <christian.koenig@amd.com> wrote:
> >>>>>>>>>>> Am 02.07.21 um 23:38 schrieb Daniel Vetter:
> >>>>>>>>>>>> This is a very confusingly named function, because not just does it
> >>>>>>>>>>>> init an object, it arms it and provides a point of no return for
> >>>>>>>>>>>> pushing a job into the scheduler. It would be nice if that's a bit
> >>>>>>>>>>>> clearer in the interface.
> >>>>>>>>>>>>
> >>>>>>>>>>>> But the real reason is that I want to push the dependency tracking
> >>>>>>>>>>>> helpers into the scheduler code, and that means drm_sched_job_init
> >>>>>>>>>>>> must be called a lot earlier, without arming the job.
> >>>>>>>>>>>>
> >>>>>>>>>>>> v2:
> >>>>>>>>>>>> - don't change .gitignore (Steven)
> >>>>>>>>>>>> - don't forget v3d (Emma)
> >>>>>>>>>>>>
> >>>>>>>>>>>> v3: Emma noticed that I leak the memory allocated in
> >>>>>>>>>>>> drm_sched_job_init if we bail out before the point of no return in
> >>>>>>>>>>>> subsequent driver patches. To be able to fix this change
> >>>>>>>>>>>> drm_sched_job_cleanup() so it can handle being called both before and
> >>>>>>>>>>>> after drm_sched_job_arm().
> >>>>>>>>>>> Thinking more about this, I'm not sure if this really works.
> >>>>>>>>>>>
> >>>>>>>>>>> See drm_sched_job_init() was also calling drm_sched_entity_select_rq()
> >>>>>>>>>>> to update the entity->rq association.
> >>>>>>>>>>>
> >>>>>>>>>>> And that can only be done later on when we arm the fence as well.
> >>>>>>>>>> Hm yeah, but that's a bug in the existing code I think: We already
> >>>>>>>>>> fail to clean up if we fail to allocate the fences. So I think the
> >>>>>>>>>> right thing to do here is to split the checks into job_init, and do
> >>>>>>>>>> the actual arming/rq selection in job_arm? I'm not entirely sure
> >>>>>>>>>> what's all going on there, the first check looks a bit like trying to
> >>>>>>>>>> schedule before the entity is set up, which is a driver bug and should
> >>>>>>>>>> have a WARN_ON?
> >>>>>>>>> No you misunderstood me, the problem is something else.
> >>>>>>>>>
> >>>>>>>>> You asked previously why the call to drm_sched_job_init() was so late in
> >>>>>>>>> the CS.
> >>>>>>>>>
> >>>>>>>>> The reason for this was not alone the scheduler fence init, but also the
> >>>>>>>>> call to drm_sched_entity_select_rq().
> >>>>>>>> Ah ok, I think I can fix that. Needs a prep patch to first make
> >>>>>>>> drm_sched_entity_select infallible, then should be easy to do.
> >>>>>>>>
> >>>>>>>>>> The 2nd check around last_scheduled I have honeslty no idea what it's
> >>>>>>>>>> even trying to do.
> >>>>>>>>> You mean that here?
> >>>>>>>>>
> >>>>>>>>>              fence = READ_ONCE(entity->last_scheduled);
> >>>>>>>>>              if (fence && !dma_fence_is_signaled(fence))
> >>>>>>>>>                      return;
> >>>>>>>>>
> >>>>>>>>> This makes sure that load balancing is not moving the entity to a
> >>>>>>>>> different scheduler while there are still jobs running from this entity
> >>>>>>>>> on the hardware,
> >>>>>>>> Yeah after a nap that idea crossed my mind too. But now I have locking
> >>>>>>>> questions, afaiui the scheduler thread updates this, without taking
> >>>>>>>> any locks - entity dequeuing is lockless. And here we read the fence
> >>>>>>>> and then seem to yolo check whether it's signalled? What's preventing
> >>>>>>>> a use-after-free here? There's no rcu or anything going on here at
> >>>>>>>> all, and it's outside of the spinlock section, which starts a bit
> >>>>>>>> further down.
> >>>>>>> The last_scheduled fence of an entity can only change when there are
> >>>>>>> jobs on the entities queued, and we have just ruled that out in the
> >>>>>>> check before.
> >>>>>> There aren't any barriers, so the cpu could easily run the two checks
> >>>>>> the other way round. I'll ponder this and figure out where exactly we
> >>>>>> need docs for the constraint and/or barriers to make this work as
> >>>>>> intended. As-is I'm not seeing how it does ...
> >>>>> spsc_queue_count() provides the necessary barrier with the atomic_read().
> >>>> atomic_t is fully unordered, except when it's a read-modify-write
> >>> Wasn't awake yet, I think the rule is read-modify-write and return
> >>> previous value gives you full barrier. So stuff like cmpxchg, but also
> >>> a few others. See atomic_t.txt under ODERING heading (yes that
> >>> maintainer refuses to accept .rst so I can't just link you to the
> >>> right section, it's silly). get/set and even RMW atomic ops that don't
> >>> return anything are all fully unordered.
> >> As far as I know that not completely correct. The rules around atomics i
> >> once learned are:
> >>
> >> 1. Everything which modifies something is a write barrier.
> >> 2. Everything which returns something is a read barrier.
> >>
> >> And I know a whole bunch of use cases where this is relied upon in the core
> >> kernel, so I'm pretty sure that's correct.
> > That's against what the doc says, and also it would mean stuff like
> > atomic_read_acquire or smp_mb__after/before_atomic is completely pointless.
> >
> > On x86 you're right, anywhere else where there's no total store ordering I
> > you're wrong.
>
> Good to know. I always thought that atomic_read_acquire() was just for
> documentation purpose.

Maybe you mixed it up with C++ atomics (which I think are now also in
C)? Those are strongly ordered by default (you can get the weakly
ordered kernel-style one too). It's a bit unfortunate that the default
semantics are exactly opposite between kernel and userspace :-/

> > If there's code that relies on this it needs to be fixed and properly
> > documented. I did go through the squeue code a bit, and might be better to
> > just replace this with a core data structure.
>
> Well the spsc was especially crafted for this use case and performed
> quite a bit better then a double linked list.

Yeah  double-linked list is awful.

> Or what core data structure do you have in mind?

Hm I thought there's a ready-made queue primitive, but there's just
llist.h. Which I think is roughly what the scheduler queue also does.
Minus the atomic_t for counting how many there are, and aside from the
tracepoints I don't think we're using those anywhere, we just check
for is_empty in the code (from a quick look only).
-Daniel

>
> Christian.
>
> > -Daniel
> >
> >> In this case the write barrier is the atomic_dec() in spsc_queue_pop() and
> >> the read barrier is the aromic_read() in spsc_queue_count().
> >>
> >> The READ_ONCE() is actually not even necessary as far as I can see.
> >>
> >> Christian.
> >>
> >>> -Daniel
> >>>
> >>>
> >>>> atomic op, then it's a full barrier. So yeah you need more here. But
> >>>> also since you only need a read barrier on one side, and a write
> >>>> barrier on the other, you don't actually need a cpu barriers on x86.
> >>>> And READ_ONCE gives you the compiler barrier on one side at least, I
> >>>> haven't found it on the writer side yet.
> >>>>
> >>>>> But yes a comment would be really nice here. I had to think for a while
> >>>>> why we don't need this as well.
> >>>> I'm typing a patch, which after a night's sleep I realized has the
> >>>> wrong barriers. And now I'm also typing some doc improvements for
> >>>> drm_sched_entity and related functions.
> >>>>
> >>>>> Christian.
> >>>>>
> >>>>>> -Daniel
> >>>>>>
> >>>>>>> Christian.
> >>>>>>>
> >>>>>>>
> >>>>>>>> -Daniel
> >>>>>>>>
> >>>>>>>>> Regards
> >>>>>>>>> Christian.
> >>>>>>>>>
> >>>>>>>>>> -Daniel
> >>>>>>>>>>
> >>>>>>>>>>> Christian.
> >>>>>>>>>>>
> >>>>>>>>>>>> Also improve the kerneldoc for this.
> >>>>>>>>>>>>
> >>>>>>>>>>>> Acked-by: Steven Price <steven.price@arm.com> (v2)
> >>>>>>>>>>>> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> >>>>>>>>>>>> Cc: Lucas Stach <l.stach@pengutronix.de>
> >>>>>>>>>>>> Cc: Russell King <linux+etnaviv@armlinux.org.uk>
> >>>>>>>>>>>> Cc: Christian Gmeiner <christian.gmeiner@gmail.com>
> >>>>>>>>>>>> Cc: Qiang Yu <yuq825@gmail.com>
> >>>>>>>>>>>> Cc: Rob Herring <robh@kernel.org>
> >>>>>>>>>>>> Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com>
> >>>>>>>>>>>> Cc: Steven Price <steven.price@arm.com>
> >>>>>>>>>>>> Cc: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
> >>>>>>>>>>>> Cc: David Airlie <airlied@linux.ie>
> >>>>>>>>>>>> Cc: Daniel Vetter <daniel@ffwll.ch>
> >>>>>>>>>>>> Cc: Sumit Semwal <sumit.semwal@linaro.org>
> >>>>>>>>>>>> Cc: "Christian König" <christian.koenig@amd.com>
> >>>>>>>>>>>> Cc: Masahiro Yamada <masahiroy@kernel.org>
> >>>>>>>>>>>> Cc: Kees Cook <keescook@chromium.org>
> >>>>>>>>>>>> Cc: Adam Borowski <kilobyte@angband.pl>
> >>>>>>>>>>>> Cc: Nick Terrell <terrelln@fb.com>
> >>>>>>>>>>>> Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
> >>>>>>>>>>>> Cc: Paul Menzel <pmenzel@molgen.mpg.de>
> >>>>>>>>>>>> Cc: Sami Tolvanen <samitolvanen@google.com>
> >>>>>>>>>>>> Cc: Viresh Kumar <viresh.kumar@linaro.org>
> >>>>>>>>>>>> Cc: Alex Deucher <alexander.deucher@amd.com>
> >>>>>>>>>>>> Cc: Dave Airlie <airlied@redhat.com>
> >>>>>>>>>>>> Cc: Nirmoy Das <nirmoy.das@amd.com>
> >>>>>>>>>>>> Cc: Deepak R Varma <mh12gx2825@gmail.com>
> >>>>>>>>>>>> Cc: Lee Jones <lee.jones@linaro.org>
> >>>>>>>>>>>> Cc: Kevin Wang <kevin1.wang@amd.com>
> >>>>>>>>>>>> Cc: Chen Li <chenli@uniontech.com>
> >>>>>>>>>>>> Cc: Luben Tuikov <luben.tuikov@amd.com>
> >>>>>>>>>>>> Cc: "Marek Olšák" <marek.olsak@amd.com>
> >>>>>>>>>>>> Cc: Dennis Li <Dennis.Li@amd.com>
> >>>>>>>>>>>> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> >>>>>>>>>>>> Cc: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
> >>>>>>>>>>>> Cc: Sonny Jiang <sonny.jiang@amd.com>
> >>>>>>>>>>>> Cc: Boris Brezillon <boris.brezillon@collabora.com>
> >>>>>>>>>>>> Cc: Tian Tao <tiantao6@hisilicon.com>
> >>>>>>>>>>>> Cc: Jack Zhang <Jack.Zhang1@amd.com>
> >>>>>>>>>>>> Cc: etnaviv@lists.freedesktop.org
> >>>>>>>>>>>> Cc: lima@lists.freedesktop.org
> >>>>>>>>>>>> Cc: linux-media@vger.kernel.org
> >>>>>>>>>>>> Cc: linaro-mm-sig@lists.linaro.org
> >>>>>>>>>>>> Cc: Emma Anholt <emma@anholt.net>
> >>>>>>>>>>>> ---
> >>>>>>>>>>>>        drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c   |  2 ++
> >>>>>>>>>>>>        drivers/gpu/drm/amd/amdgpu/amdgpu_job.c  |  2 ++
> >>>>>>>>>>>>        drivers/gpu/drm/etnaviv/etnaviv_sched.c  |  2 ++
> >>>>>>>>>>>>        drivers/gpu/drm/lima/lima_sched.c        |  2 ++
> >>>>>>>>>>>>        drivers/gpu/drm/panfrost/panfrost_job.c  |  2 ++
> >>>>>>>>>>>>        drivers/gpu/drm/scheduler/sched_entity.c |  6 ++--
> >>>>>>>>>>>>        drivers/gpu/drm/scheduler/sched_fence.c  | 17 +++++----
> >>>>>>>>>>>>        drivers/gpu/drm/scheduler/sched_main.c   | 46 +++++++++++++++++++++---
> >>>>>>>>>>>>        drivers/gpu/drm/v3d/v3d_gem.c            |  2 ++
> >>>>>>>>>>>>        include/drm/gpu_scheduler.h              |  7 +++-
> >>>>>>>>>>>>        10 files changed, 74 insertions(+), 14 deletions(-)
> >>>>>>>>>>>>
> >>>>>>>>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> >>>>>>>>>>>> index c5386d13eb4a..a4ec092af9a7 100644
> >>>>>>>>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> >>>>>>>>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> >>>>>>>>>>>> @@ -1226,6 +1226,8 @@ static int amdgpu_cs_submit(struct amdgpu_cs_parser *p,
> >>>>>>>>>>>>            if (r)
> >>>>>>>>>>>>                    goto error_unlock;
> >>>>>>>>>>>>
> >>>>>>>>>>>> +     drm_sched_job_arm(&job->base);
> >>>>>>>>>>>> +
> >>>>>>>>>>>>            /* No memory allocation is allowed while holding the notifier lock.
> >>>>>>>>>>>>             * The lock is held until amdgpu_cs_submit is finished and fence is
> >>>>>>>>>>>>             * added to BOs.
> >>>>>>>>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
> >>>>>>>>>>>> index d33e6d97cc89..5ddb955d2315 100644
> >>>>>>>>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
> >>>>>>>>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
> >>>>>>>>>>>> @@ -170,6 +170,8 @@ int amdgpu_job_submit(struct amdgpu_job *job, struct drm_sched_entity *entity,
> >>>>>>>>>>>>            if (r)
> >>>>>>>>>>>>                    return r;
> >>>>>>>>>>>>
> >>>>>>>>>>>> +     drm_sched_job_arm(&job->base);
> >>>>>>>>>>>> +
> >>>>>>>>>>>>            *f = dma_fence_get(&job->base.s_fence->finished);
> >>>>>>>>>>>>            amdgpu_job_free_resources(job);
> >>>>>>>>>>>>            drm_sched_entity_push_job(&job->base, entity);
> >>>>>>>>>>>> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_sched.c b/drivers/gpu/drm/etnaviv/etnaviv_sched.c
> >>>>>>>>>>>> index feb6da1b6ceb..05f412204118 100644
> >>>>>>>>>>>> --- a/drivers/gpu/drm/etnaviv/etnaviv_sched.c
> >>>>>>>>>>>> +++ b/drivers/gpu/drm/etnaviv/etnaviv_sched.c
> >>>>>>>>>>>> @@ -163,6 +163,8 @@ int etnaviv_sched_push_job(struct drm_sched_entity *sched_entity,
> >>>>>>>>>>>>            if (ret)
> >>>>>>>>>>>>                    goto out_unlock;
> >>>>>>>>>>>>
> >>>>>>>>>>>> +     drm_sched_job_arm(&submit->sched_job);
> >>>>>>>>>>>> +
> >>>>>>>>>>>>            submit->out_fence = dma_fence_get(&submit->sched_job.s_fence->finished);
> >>>>>>>>>>>>            submit->out_fence_id = idr_alloc_cyclic(&submit->gpu->fence_idr,
> >>>>>>>>>>>>                                                    submit->out_fence, 0,
> >>>>>>>>>>>> diff --git a/drivers/gpu/drm/lima/lima_sched.c b/drivers/gpu/drm/lima/lima_sched.c
> >>>>>>>>>>>> index dba8329937a3..38f755580507 100644
> >>>>>>>>>>>> --- a/drivers/gpu/drm/lima/lima_sched.c
> >>>>>>>>>>>> +++ b/drivers/gpu/drm/lima/lima_sched.c
> >>>>>>>>>>>> @@ -129,6 +129,8 @@ int lima_sched_task_init(struct lima_sched_task *task,
> >>>>>>>>>>>>                    return err;
> >>>>>>>>>>>>            }
> >>>>>>>>>>>>
> >>>>>>>>>>>> +     drm_sched_job_arm(&task->base);
> >>>>>>>>>>>> +
> >>>>>>>>>>>>            task->num_bos = num_bos;
> >>>>>>>>>>>>            task->vm = lima_vm_get(vm);
> >>>>>>>>>>>>
> >>>>>>>>>>>> diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
> >>>>>>>>>>>> index 71a72fb50e6b..2992dc85325f 100644
> >>>>>>>>>>>> --- a/drivers/gpu/drm/panfrost/panfrost_job.c
> >>>>>>>>>>>> +++ b/drivers/gpu/drm/panfrost/panfrost_job.c
> >>>>>>>>>>>> @@ -288,6 +288,8 @@ int panfrost_job_push(struct panfrost_job *job)
> >>>>>>>>>>>>                    goto unlock;
> >>>>>>>>>>>>            }
> >>>>>>>>>>>>
> >>>>>>>>>>>> +     drm_sched_job_arm(&job->base);
> >>>>>>>>>>>> +
> >>>>>>>>>>>>            job->render_done_fence = dma_fence_get(&job->base.s_fence->finished);
> >>>>>>>>>>>>
> >>>>>>>>>>>>            ret = panfrost_acquire_object_fences(job->bos, job->bo_count,
> >>>>>>>>>>>> diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
> >>>>>>>>>>>> index 79554aa4dbb1..f7347c284886 100644
> >>>>>>>>>>>> --- a/drivers/gpu/drm/scheduler/sched_entity.c
> >>>>>>>>>>>> +++ b/drivers/gpu/drm/scheduler/sched_entity.c
> >>>>>>>>>>>> @@ -485,9 +485,9 @@ void drm_sched_entity_select_rq(struct drm_sched_entity *entity)
> >>>>>>>>>>>>         * @sched_job: job to submit
> >>>>>>>>>>>>         * @entity: scheduler entity
> >>>>>>>>>>>>         *
> >>>>>>>>>>>> - * Note: To guarantee that the order of insertion to queue matches
> >>>>>>>>>>>> - * the job's fence sequence number this function should be
> >>>>>>>>>>>> - * called with drm_sched_job_init under common lock.
> >>>>>>>>>>>> + * Note: To guarantee that the order of insertion to queue matches the job's
> >>>>>>>>>>>> + * fence sequence number this function should be called with drm_sched_job_arm()
> >>>>>>>>>>>> + * under common lock.
> >>>>>>>>>>>>         *
> >>>>>>>>>>>>         * Returns 0 for success, negative error code otherwise.
> >>>>>>>>>>>>         */
> >>>>>>>>>>>> diff --git a/drivers/gpu/drm/scheduler/sched_fence.c b/drivers/gpu/drm/scheduler/sched_fence.c
> >>>>>>>>>>>> index 69de2c76731f..c451ee9a30d7 100644
> >>>>>>>>>>>> --- a/drivers/gpu/drm/scheduler/sched_fence.c
> >>>>>>>>>>>> +++ b/drivers/gpu/drm/scheduler/sched_fence.c
> >>>>>>>>>>>> @@ -90,7 +90,7 @@ static const char *drm_sched_fence_get_timeline_name(struct dma_fence *f)
> >>>>>>>>>>>>         *
> >>>>>>>>>>>>         * Free up the fence memory after the RCU grace period.
> >>>>>>>>>>>>         */
> >>>>>>>>>>>> -static void drm_sched_fence_free(struct rcu_head *rcu)
> >>>>>>>>>>>> +void drm_sched_fence_free(struct rcu_head *rcu)
> >>>>>>>>>>>>        {
> >>>>>>>>>>>>            struct dma_fence *f = container_of(rcu, struct dma_fence, rcu);
> >>>>>>>>>>>>            struct drm_sched_fence *fence = to_drm_sched_fence(f);
> >>>>>>>>>>>> @@ -152,11 +152,10 @@ struct drm_sched_fence *to_drm_sched_fence(struct dma_fence *f)
> >>>>>>>>>>>>        }
> >>>>>>>>>>>>        EXPORT_SYMBOL(to_drm_sched_fence);
> >>>>>>>>>>>>
> >>>>>>>>>>>> -struct drm_sched_fence *drm_sched_fence_create(struct drm_sched_entity *entity,
> >>>>>>>>>>>> -                                            void *owner)
> >>>>>>>>>>>> +struct drm_sched_fence *drm_sched_fence_alloc(struct drm_sched_entity *entity,
> >>>>>>>>>>>> +                                           void *owner)
> >>>>>>>>>>>>        {
> >>>>>>>>>>>>            struct drm_sched_fence *fence = NULL;
> >>>>>>>>>>>> -     unsigned seq;
> >>>>>>>>>>>>
> >>>>>>>>>>>>            fence = kmem_cache_zalloc(sched_fence_slab, GFP_KERNEL);
> >>>>>>>>>>>>            if (fence == NULL)
> >>>>>>>>>>>> @@ -166,13 +165,19 @@ struct drm_sched_fence *drm_sched_fence_create(struct drm_sched_entity *entity,
> >>>>>>>>>>>>            fence->sched = entity->rq->sched;
> >>>>>>>>>>>>            spin_lock_init(&fence->lock);
> >>>>>>>>>>>>
> >>>>>>>>>>>> +     return fence;
> >>>>>>>>>>>> +}
> >>>>>>>>>>>> +
> >>>>>>>>>>>> +void drm_sched_fence_init(struct drm_sched_fence *fence,
> >>>>>>>>>>>> +                       struct drm_sched_entity *entity)
> >>>>>>>>>>>> +{
> >>>>>>>>>>>> +     unsigned seq;
> >>>>>>>>>>>> +
> >>>>>>>>>>>>            seq = atomic_inc_return(&entity->fence_seq);
> >>>>>>>>>>>>            dma_fence_init(&fence->scheduled, &drm_sched_fence_ops_scheduled,
> >>>>>>>>>>>>                           &fence->lock, entity->fence_context, seq);
> >>>>>>>>>>>>            dma_fence_init(&fence->finished, &drm_sched_fence_ops_finished,
> >>>>>>>>>>>>                           &fence->lock, entity->fence_context + 1, seq);
> >>>>>>>>>>>> -
> >>>>>>>>>>>> -     return fence;
> >>>>>>>>>>>>        }
> >>>>>>>>>>>>
> >>>>>>>>>>>>        module_init(drm_sched_fence_slab_init);
> >>>>>>>>>>>> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
> >>>>>>>>>>>> index 33c414d55fab..5e84e1500c32 100644
> >>>>>>>>>>>> --- a/drivers/gpu/drm/scheduler/sched_main.c
> >>>>>>>>>>>> +++ b/drivers/gpu/drm/scheduler/sched_main.c
> >>>>>>>>>>>> @@ -48,9 +48,11 @@
> >>>>>>>>>>>>        #include <linux/wait.h>
> >>>>>>>>>>>>        #include <linux/sched.h>
> >>>>>>>>>>>>        #include <linux/completion.h>
> >>>>>>>>>>>> +#include <linux/dma-resv.h>
> >>>>>>>>>>>>        #include <uapi/linux/sched/types.h>
> >>>>>>>>>>>>
> >>>>>>>>>>>>        #include <drm/drm_print.h>
> >>>>>>>>>>>> +#include <drm/drm_gem.h>
> >>>>>>>>>>>>        #include <drm/gpu_scheduler.h>
> >>>>>>>>>>>>        #include <drm/spsc_queue.h>
> >>>>>>>>>>>>
> >>>>>>>>>>>> @@ -569,7 +571,6 @@ EXPORT_SYMBOL(drm_sched_resubmit_jobs_ext);
> >>>>>>>>>>>>
> >>>>>>>>>>>>        /**
> >>>>>>>>>>>>         * drm_sched_job_init - init a scheduler job
> >>>>>>>>>>>> - *
> >>>>>>>>>>>>         * @job: scheduler job to init
> >>>>>>>>>>>>         * @entity: scheduler entity to use
> >>>>>>>>>>>>         * @owner: job owner for debugging
> >>>>>>>>>>>> @@ -577,6 +578,9 @@ EXPORT_SYMBOL(drm_sched_resubmit_jobs_ext);
> >>>>>>>>>>>>         * Refer to drm_sched_entity_push_job() documentation
> >>>>>>>>>>>>         * for locking considerations.
> >>>>>>>>>>>>         *
> >>>>>>>>>>>> + * Drivers must make sure drm_sched_job_cleanup() if this function returns
> >>>>>>>>>>>> + * successfully, even when @job is aborted before drm_sched_job_arm() is called.
> >>>>>>>>>>>> + *
> >>>>>>>>>>>>         * Returns 0 for success, negative error code otherwise.
> >>>>>>>>>>>>         */
> >>>>>>>>>>>>        int drm_sched_job_init(struct drm_sched_job *job,
> >>>>>>>>>>>> @@ -594,7 +598,7 @@ int drm_sched_job_init(struct drm_sched_job *job,
> >>>>>>>>>>>>            job->sched = sched;
> >>>>>>>>>>>>            job->entity = entity;
> >>>>>>>>>>>>            job->s_priority = entity->rq - sched->sched_rq;
> >>>>>>>>>>>> -     job->s_fence = drm_sched_fence_create(entity, owner);
> >>>>>>>>>>>> +     job->s_fence = drm_sched_fence_alloc(entity, owner);
> >>>>>>>>>>>>            if (!job->s_fence)
> >>>>>>>>>>>>                    return -ENOMEM;
> >>>>>>>>>>>>            job->id = atomic64_inc_return(&sched->job_id_count);
> >>>>>>>>>>>> @@ -606,13 +610,47 @@ int drm_sched_job_init(struct drm_sched_job *job,
> >>>>>>>>>>>>        EXPORT_SYMBOL(drm_sched_job_init);
> >>>>>>>>>>>>
> >>>>>>>>>>>>        /**
> >>>>>>>>>>>> - * drm_sched_job_cleanup - clean up scheduler job resources
> >>>>>>>>>>>> + * drm_sched_job_arm - arm a scheduler job for execution
> >>>>>>>>>>>> + * @job: scheduler job to arm
> >>>>>>>>>>>> + *
> >>>>>>>>>>>> + * This arms a scheduler job for execution. Specifically it initializes the
> >>>>>>>>>>>> + * &drm_sched_job.s_fence of @job, so that it can be attached to struct dma_resv
> >>>>>>>>>>>> + * or other places that need to track the completion of this job.
> >>>>>>>>>>>> + *
> >>>>>>>>>>>> + * Refer to drm_sched_entity_push_job() documentation for locking
> >>>>>>>>>>>> + * considerations.
> >>>>>>>>>>>>         *
> >>>>>>>>>>>> + * This can only be called if drm_sched_job_init() succeeded.
> >>>>>>>>>>>> + */
> >>>>>>>>>>>> +void drm_sched_job_arm(struct drm_sched_job *job)
> >>>>>>>>>>>> +{
> >>>>>>>>>>>> +     drm_sched_fence_init(job->s_fence, job->entity);
> >>>>>>>>>>>> +}
> >>>>>>>>>>>> +EXPORT_SYMBOL(drm_sched_job_arm);
> >>>>>>>>>>>> +
> >>>>>>>>>>>> +/**
> >>>>>>>>>>>> + * drm_sched_job_cleanup - clean up scheduler job resources
> >>>>>>>>>>>>         * @job: scheduler job to clean up
> >>>>>>>>>>>> + *
> >>>>>>>>>>>> + * Cleans up the resources allocated with drm_sched_job_init().
> >>>>>>>>>>>> + *
> >>>>>>>>>>>> + * Drivers should call this from their error unwind code if @job is aborted
> >>>>>>>>>>>> + * before drm_sched_job_arm() is called.
> >>>>>>>>>>>> + *
> >>>>>>>>>>>> + * After that point of no return @job is committed to be executed by the
> >>>>>>>>>>>> + * scheduler, and this function should be called from the
> >>>>>>>>>>>> + * &drm_sched_backend_ops.free_job callback.
> >>>>>>>>>>>>         */
> >>>>>>>>>>>>        void drm_sched_job_cleanup(struct drm_sched_job *job)
> >>>>>>>>>>>>        {
> >>>>>>>>>>>> -     dma_fence_put(&job->s_fence->finished);
> >>>>>>>>>>>> +     if (!kref_read(&job->s_fence->finished.refcount)) {
> >>>>>>>>>>>> +             /* drm_sched_job_arm() has been called */
> >>>>>>>>>>>> +             dma_fence_put(&job->s_fence->finished);
> >>>>>>>>>>>> +     } else {
> >>>>>>>>>>>> +             /* aborted job before committing to run it */
> >>>>>>>>>>>> +             drm_sched_fence_free(&job->s_fence->finished.rcu);
> >>>>>>>>>>>> +     }
> >>>>>>>>>>>> +
> >>>>>>>>>>>>            job->s_fence = NULL;
> >>>>>>>>>>>>        }
> >>>>>>>>>>>>        EXPORT_SYMBOL(drm_sched_job_cleanup);
> >>>>>>>>>>>> diff --git a/drivers/gpu/drm/v3d/v3d_gem.c b/drivers/gpu/drm/v3d/v3d_gem.c
> >>>>>>>>>>>> index 4eb354226972..5c3a99027ecd 100644
> >>>>>>>>>>>> --- a/drivers/gpu/drm/v3d/v3d_gem.c
> >>>>>>>>>>>> +++ b/drivers/gpu/drm/v3d/v3d_gem.c
> >>>>>>>>>>>> @@ -475,6 +475,8 @@ v3d_push_job(struct v3d_file_priv *v3d_priv,
> >>>>>>>>>>>>            if (ret)
> >>>>>>>>>>>>                    return ret;
> >>>>>>>>>>>>
> >>>>>>>>>>>> +     drm_sched_job_arm(&job->base);
> >>>>>>>>>>>> +
> >>>>>>>>>>>>            job->done_fence = dma_fence_get(&job->base.s_fence->finished);
> >>>>>>>>>>>>
> >>>>>>>>>>>>            /* put by scheduler job completion */
> >>>>>>>>>>>> diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
> >>>>>>>>>>>> index 88ae7f331bb1..83afc3aa8e2f 100644
> >>>>>>>>>>>> --- a/include/drm/gpu_scheduler.h
> >>>>>>>>>>>> +++ b/include/drm/gpu_scheduler.h
> >>>>>>>>>>>> @@ -348,6 +348,7 @@ void drm_sched_fini(struct drm_gpu_scheduler *sched);
> >>>>>>>>>>>>        int drm_sched_job_init(struct drm_sched_job *job,
> >>>>>>>>>>>>                           struct drm_sched_entity *entity,
> >>>>>>>>>>>>                           void *owner);
> >>>>>>>>>>>> +void drm_sched_job_arm(struct drm_sched_job *job);
> >>>>>>>>>>>>        void drm_sched_entity_modify_sched(struct drm_sched_entity *entity,
> >>>>>>>>>>>>                                        struct drm_gpu_scheduler **sched_list,
> >>>>>>>>>>>>                                           unsigned int num_sched_list);
> >>>>>>>>>>>> @@ -387,8 +388,12 @@ void drm_sched_entity_set_priority(struct drm_sched_entity *entity,
> >>>>>>>>>>>>                                       enum drm_sched_priority priority);
> >>>>>>>>>>>>        bool drm_sched_entity_is_ready(struct drm_sched_entity *entity);
> >>>>>>>>>>>>
> >>>>>>>>>>>> -struct drm_sched_fence *drm_sched_fence_create(
> >>>>>>>>>>>> +struct drm_sched_fence *drm_sched_fence_alloc(
> >>>>>>>>>>>>            struct drm_sched_entity *s_entity, void *owner);
> >>>>>>>>>>>> +void drm_sched_fence_init(struct drm_sched_fence *fence,
> >>>>>>>>>>>> +                       struct drm_sched_entity *entity);
> >>>>>>>>>>>> +void drm_sched_fence_free(struct rcu_head *rcu);
> >>>>>>>>>>>> +
> >>>>>>>>>>>>        void drm_sched_fence_scheduled(struct drm_sched_fence *fence);
> >>>>>>>>>>>>        void drm_sched_fence_finished(struct drm_sched_fence *fence);
> >>>>>>>>>>>>
> >>>> --
> >>>> Daniel Vetter
> >>>> Software Engineer, Intel Corporation
> >>>> https://nam11.safelinks.protection.outlook.com/?url=http%3A%2F%2Fblog.ffwll.ch%2F&amp;data=04%7C01%7Cchristian.koenig%40amd.com%7C7086790381b9415f60e708d941f78266%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637613353580226578%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=9GhYoGHD6TlcrW5dvT9Z%2BFukW%2F8%2BicK2t8180coEsJY%3D&amp;reserved=0
> >>>
> >>> --
> >>> Daniel Vetter
> >>> Software Engineer, Intel Corporation
> >>> https://nam11.safelinks.protection.outlook.com/?url=http%3A%2F%2Fblog.ffwll.ch%2F&amp;data=04%7C01%7Cchristian.koenig%40amd.com%7C7086790381b9415f60e708d941f78266%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637613353580236571%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=Yt%2FirDjTmtDUjQS1xlYg4x5mz82cHkNyLPkNNpO31ro%3D&amp;reserved=0
>


-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

WARNING: multiple messages have this Message-ID
From: Daniel Vetter <daniel@ffwll.ch>
To: "Christian König" <christian.koenig@amd.com>
Cc: "Emma Anholt" <emma@anholt.net>,
	"Adam Borowski" <kilobyte@angband.pl>,
	"David Airlie" <airlied@linux.ie>,
	"Viresh Kumar" <viresh.kumar@linaro.org>,
	"DRI Development" <dri-devel@lists.freedesktop.org>,
	"Sonny Jiang" <sonny.jiang@amd.com>,
	"Nirmoy Das" <nirmoy.das@amd.com>,
	"Daniel Vetter" <daniel.vetter@intel.com>,
	"Lee Jones" <lee.jones@linaro.org>,
	"Jack Zhang" <Jack.Zhang1@amd.com>,
	lima@lists.freedesktop.org,
	"Mauro Carvalho Chehab" <mchehab+huawei@kernel.org>,
	"Masahiro Yamada" <masahiroy@kernel.org>,
	"Steven Price" <steven.price@arm.com>,
	"Luben Tuikov" <luben.tuikov@amd.com>,
	"Alyssa Rosenzweig" <alyssa.rosenzweig@collabora.com>,
	"Sami Tolvanen" <samitolvanen@google.com>,
	"Russell King" <linux+etnaviv@armlinux.org.uk>,
	"Dave Airlie" <airlied@redhat.com>,
	"Dennis Li" <Dennis.Li@amd.com>, "Chen Li" <chenli@uniontech.com>,
	"Paul Menzel" <pmenzel@molgen.mpg.de>,
	"Kees Cook" <keescook@chromium.org>,
	"Marek Olšák" <marek.olsak@amd.com>,
	"Kevin Wang" <kevin1.wang@amd.com>,
	"The etnaviv authors" <etnaviv@lists.freedesktop.org>,
	"moderated list:DMA BUFFER SHARING FRAMEWORK"
	<linaro-mm-sig@lists.linaro.org>,
	"Nick Terrell" <terrelln@fb.com>,
	"Deepak R Varma" <mh12gx2825@gmail.com>,
	"Tomeu Vizoso" <tomeu.vizoso@collabora.com>,
	"Boris Brezillon" <boris.brezillon@collabora.com>,
	"Qiang Yu" <yuq825@gmail.com>,
	"Alex Deucher" <alexander.deucher@amd.com>,
	"Tian Tao" <tiantao6@hisilicon.com>,
	"open list:DMA BUFFER SHARING FRAMEWORK"
	<linux-media@vger.kernel.org>
Subject: Re: [PATCH v2 01/11] drm/sched: Split drm_sched_job_init
Date: Thu, 8 Jul 2021 13:20:32 +0200	[thread overview]
Message-ID: <CAKMK7uE4H2nsAYSAQGB0R7YTHUFvfNmshE2Bqy0uSdHomPxo=A@mail.gmail.com> (raw)
In-Reply-To: <700b6419-4d3c-9cc8-f8bd-0d7d134df546@amd.com>

On Thu, Jul 8, 2021 at 12:54 PM Christian König
<christian.koenig@amd.com> wrote:
>
> Am 08.07.21 um 12:02 schrieb Daniel Vetter:
> > On Thu, Jul 08, 2021 at 09:53:00AM +0200, Christian König wrote:
> >> Am 08.07.21 um 09:19 schrieb Daniel Vetter:
> >>> On Thu, Jul 8, 2021 at 9:09 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> >>>> On Thu, Jul 8, 2021 at 8:56 AM Christian König <christian.koenig@amd.com> wrote:
> >>>>> Am 07.07.21 um 18:32 schrieb Daniel Vetter:
> >>>>>> On Wed, Jul 7, 2021 at 2:58 PM Christian König <christian.koenig@amd.com> wrote:
> >>>>>>> Am 07.07.21 um 14:13 schrieb Daniel Vetter:
> >>>>>>>> On Wed, Jul 7, 2021 at 1:57 PM Christian König <christian.koenig@amd.com> wrote:
> >>>>>>>>> Am 07.07.21 um 13:14 schrieb Daniel Vetter:
> >>>>>>>>>> On Wed, Jul 7, 2021 at 11:30 AM Christian König
> >>>>>>>>>> <christian.koenig@amd.com> wrote:
> >>>>>>>>>>> Am 02.07.21 um 23:38 schrieb Daniel Vetter:
> >>>>>>>>>>>> This is a very confusingly named function, because not just does it
> >>>>>>>>>>>> init an object, it arms it and provides a point of no return for
> >>>>>>>>>>>> pushing a job into the scheduler. It would be nice if that's a bit
> >>>>>>>>>>>> clearer in the interface.
> >>>>>>>>>>>>
> >>>>>>>>>>>> But the real reason is that I want to push the dependency tracking
> >>>>>>>>>>>> helpers into the scheduler code, and that means drm_sched_job_init
> >>>>>>>>>>>> must be called a lot earlier, without arming the job.
> >>>>>>>>>>>>
> >>>>>>>>>>>> v2:
> >>>>>>>>>>>> - don't change .gitignore (Steven)
> >>>>>>>>>>>> - don't forget v3d (Emma)
> >>>>>>>>>>>>
> >>>>>>>>>>>> v3: Emma noticed that I leak the memory allocated in
> >>>>>>>>>>>> drm_sched_job_init if we bail out before the point of no return in
> >>>>>>>>>>>> subsequent driver patches. To be able to fix this change
> >>>>>>>>>>>> drm_sched_job_cleanup() so it can handle being called both before and
> >>>>>>>>>>>> after drm_sched_job_arm().
> >>>>>>>>>>> Thinking more about this, I'm not sure if this really works.
> >>>>>>>>>>>
> >>>>>>>>>>> See drm_sched_job_init() was also calling drm_sched_entity_select_rq()
> >>>>>>>>>>> to update the entity->rq association.
> >>>>>>>>>>>
> >>>>>>>>>>> And that can only be done later on when we arm the fence as well.
> >>>>>>>>>> Hm yeah, but that's a bug in the existing code I think: We already
> >>>>>>>>>> fail to clean up if we fail to allocate the fences. So I think the
> >>>>>>>>>> right thing to do here is to split the checks into job_init, and do
> >>>>>>>>>> the actual arming/rq selection in job_arm? I'm not entirely sure
> >>>>>>>>>> what's all going on there, the first check looks a bit like trying to
> >>>>>>>>>> schedule before the entity is set up, which is a driver bug and should
> >>>>>>>>>> have a WARN_ON?
> >>>>>>>>> No you misunderstood me, the problem is something else.
> >>>>>>>>>
> >>>>>>>>> You asked previously why the call to drm_sched_job_init() was so late in
> >>>>>>>>> the CS.
> >>>>>>>>>
> >>>>>>>>> The reason for this was not alone the scheduler fence init, but also the
> >>>>>>>>> call to drm_sched_entity_select_rq().
> >>>>>>>> Ah ok, I think I can fix that. Needs a prep patch to first make
> >>>>>>>> drm_sched_entity_select infallible, then should be easy to do.
> >>>>>>>>
> >>>>>>>>>> The 2nd check around last_scheduled I have honeslty no idea what it's
> >>>>>>>>>> even trying to do.
> >>>>>>>>> You mean that here?
> >>>>>>>>>
> >>>>>>>>>              fence = READ_ONCE(entity->last_scheduled);
> >>>>>>>>>              if (fence && !dma_fence_is_signaled(fence))
> >>>>>>>>>                      return;
> >>>>>>>>>
> >>>>>>>>> This makes sure that load balancing is not moving the entity to a
> >>>>>>>>> different scheduler while there are still jobs running from this entity
> >>>>>>>>> on the hardware,
> >>>>>>>> Yeah after a nap that idea crossed my mind too. But now I have locking
> >>>>>>>> questions, afaiui the scheduler thread updates this, without taking
> >>>>>>>> any locks - entity dequeuing is lockless. And here we read the fence
> >>>>>>>> and then seem to yolo check whether it's signalled? What's preventing
> >>>>>>>> a use-after-free here? There's no rcu or anything going on here at
> >>>>>>>> all, and it's outside of the spinlock section, which starts a bit
> >>>>>>>> further down.
> >>>>>>> The last_scheduled fence of an entity can only change when there are
> >>>>>>> jobs on the entities queued, and we have just ruled that out in the
> >>>>>>> check before.
> >>>>>> There aren't any barriers, so the cpu could easily run the two checks
> >>>>>> the other way round. I'll ponder this and figure out where exactly we
> >>>>>> need docs for the constraint and/or barriers to make this work as
> >>>>>> intended. As-is I'm not seeing how it does ...
> >>>>> spsc_queue_count() provides the necessary barrier with the atomic_read().
> >>>> atomic_t is fully unordered, except when it's a read-modify-write
> >>> Wasn't awake yet, I think the rule is read-modify-write and return
> >>> previous value gives you full barrier. So stuff like cmpxchg, but also
> >>> a few others. See atomic_t.txt under ODERING heading (yes that
> >>> maintainer refuses to accept .rst so I can't just link you to the
> >>> right section, it's silly). get/set and even RMW atomic ops that don't
> >>> return anything are all fully unordered.
> >> As far as I know that not completely correct. The rules around atomics i
> >> once learned are:
> >>
> >> 1. Everything which modifies something is a write barrier.
> >> 2. Everything which returns something is a read barrier.
> >>
> >> And I know a whole bunch of use cases where this is relied upon in the core
> >> kernel, so I'm pretty sure that's correct.
> > That's against what the doc says, and also it would mean stuff like
> > atomic_read_acquire or smp_mb__after/before_atomic is completely pointless.
> >
> > On x86 you're right, anywhere else where there's no total store ordering I
> > you're wrong.
>
> Good to know. I always thought that atomic_read_acquire() was just for
> documentation purpose.

Maybe you mixed it up with C++ atomics (which I think are now also in
C)? Those are strongly ordered by default (you can get the weakly
ordered kernel-style one too). It's a bit unfortunate that the default
semantics are exactly opposite between kernel and userspace :-/

> > If there's code that relies on this it needs to be fixed and properly
> > documented. I did go through the squeue code a bit, and might be better to
> > just replace this with a core data structure.
>
> Well the spsc was especially crafted for this use case and performed
> quite a bit better then a double linked list.

Yeah  double-linked list is awful.

> Or what core data structure do you have in mind?

Hm I thought there's a ready-made queue primitive, but there's just
llist.h. Which I think is roughly what the scheduler queue also does.
Minus the atomic_t for counting how many there are, and aside from the
tracepoints I don't think we're using those anywhere, we just check
for is_empty in the code (from a quick look only).
-Daniel

>
> Christian.
>
> > -Daniel
> >
> >> In this case the write barrier is the atomic_dec() in spsc_queue_pop() and
> >> the read barrier is the aromic_read() in spsc_queue_count().
> >>
> >> The READ_ONCE() is actually not even necessary as far as I can see.
> >>
> >> Christian.
> >>
> >>> -Daniel
> >>>
> >>>
> >>>> atomic op, then it's a full barrier. So yeah you need more here. But
> >>>> also since you only need a read barrier on one side, and a write
> >>>> barrier on the other, you don't actually need a cpu barriers on x86.
> >>>> And READ_ONCE gives you the compiler barrier on one side at least, I
> >>>> haven't found it on the writer side yet.
> >>>>
> >>>>> But yes a comment would be really nice here. I had to think for a while
> >>>>> why we don't need this as well.
> >>>> I'm typing a patch, which after a night's sleep I realized has the
> >>>> wrong barriers. And now I'm also typing some doc improvements for
> >>>> drm_sched_entity and related functions.
> >>>>
> >>>>> Christian.
> >>>>>
> >>>>>> -Daniel
> >>>>>>
> >>>>>>> Christian.
> >>>>>>>
> >>>>>>>
> >>>>>>>> -Daniel
> >>>>>>>>
> >>>>>>>>> Regards
> >>>>>>>>> Christian.
> >>>>>>>>>
> >>>>>>>>>> -Daniel
> >>>>>>>>>>
> >>>>>>>>>>> Christian.
> >>>>>>>>>>>
> >>>>>>>>>>>> Also improve the kerneldoc for this.
> >>>>>>>>>>>>
> >>>>>>>>>>>> Acked-by: Steven Price <steven.price@arm.com> (v2)
> >>>>>>>>>>>> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> >>>>>>>>>>>> Cc: Lucas Stach <l.stach@pengutronix.de>
> >>>>>>>>>>>> Cc: Russell King <linux+etnaviv@armlinux.org.uk>
> >>>>>>>>>>>> Cc: Christian Gmeiner <christian.gmeiner@gmail.com>
> >>>>>>>>>>>> Cc: Qiang Yu <yuq825@gmail.com>
> >>>>>>>>>>>> Cc: Rob Herring <robh@kernel.org>
> >>>>>>>>>>>> Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com>
> >>>>>>>>>>>> Cc: Steven Price <steven.price@arm.com>
> >>>>>>>>>>>> Cc: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
> >>>>>>>>>>>> Cc: David Airlie <airlied@linux.ie>
> >>>>>>>>>>>> Cc: Daniel Vetter <daniel@ffwll.ch>
> >>>>>>>>>>>> Cc: Sumit Semwal <sumit.semwal@linaro.org>
> >>>>>>>>>>>> Cc: "Christian König" <christian.koenig@amd.com>
> >>>>>>>>>>>> Cc: Masahiro Yamada <masahiroy@kernel.org>
> >>>>>>>>>>>> Cc: Kees Cook <keescook@chromium.org>
> >>>>>>>>>>>> Cc: Adam Borowski <kilobyte@angband.pl>
> >>>>>>>>>>>> Cc: Nick Terrell <terrelln@fb.com>
> >>>>>>>>>>>> Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
> >>>>>>>>>>>> Cc: Paul Menzel <pmenzel@molgen.mpg.de>
> >>>>>>>>>>>> Cc: Sami Tolvanen <samitolvanen@google.com>
> >>>>>>>>>>>> Cc: Viresh Kumar <viresh.kumar@linaro.org>
> >>>>>>>>>>>> Cc: Alex Deucher <alexander.deucher@amd.com>
> >>>>>>>>>>>> Cc: Dave Airlie <airlied@redhat.com>
> >>>>>>>>>>>> Cc: Nirmoy Das <nirmoy.das@amd.com>
> >>>>>>>>>>>> Cc: Deepak R Varma <mh12gx2825@gmail.com>
> >>>>>>>>>>>> Cc: Lee Jones <lee.jones@linaro.org>
> >>>>>>>>>>>> Cc: Kevin Wang <kevin1.wang@amd.com>
> >>>>>>>>>>>> Cc: Chen Li <chenli@uniontech.com>
> >>>>>>>>>>>> Cc: Luben Tuikov <luben.tuikov@amd.com>
> >>>>>>>>>>>> Cc: "Marek Olšák" <marek.olsak@amd.com>
> >>>>>>>>>>>> Cc: Dennis Li <Dennis.Li@amd.com>
> >>>>>>>>>>>> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> >>>>>>>>>>>> Cc: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
> >>>>>>>>>>>> Cc: Sonny Jiang <sonny.jiang@amd.com>
> >>>>>>>>>>>> Cc: Boris Brezillon <boris.brezillon@collabora.com>
> >>>>>>>>>>>> Cc: Tian Tao <tiantao6@hisilicon.com>
> >>>>>>>>>>>> Cc: Jack Zhang <Jack.Zhang1@amd.com>
> >>>>>>>>>>>> Cc: etnaviv@lists.freedesktop.org
> >>>>>>>>>>>> Cc: lima@lists.freedesktop.org
> >>>>>>>>>>>> Cc: linux-media@vger.kernel.org
> >>>>>>>>>>>> Cc: linaro-mm-sig@lists.linaro.org
> >>>>>>>>>>>> Cc: Emma Anholt <emma@anholt.net>
> >>>>>>>>>>>> ---
> >>>>>>>>>>>>        drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c   |  2 ++
> >>>>>>>>>>>>        drivers/gpu/drm/amd/amdgpu/amdgpu_job.c  |  2 ++
> >>>>>>>>>>>>        drivers/gpu/drm/etnaviv/etnaviv_sched.c  |  2 ++
> >>>>>>>>>>>>        drivers/gpu/drm/lima/lima_sched.c        |  2 ++
> >>>>>>>>>>>>        drivers/gpu/drm/panfrost/panfrost_job.c  |  2 ++
> >>>>>>>>>>>>        drivers/gpu/drm/scheduler/sched_entity.c |  6 ++--
> >>>>>>>>>>>>        drivers/gpu/drm/scheduler/sched_fence.c  | 17 +++++----
> >>>>>>>>>>>>        drivers/gpu/drm/scheduler/sched_main.c   | 46 +++++++++++++++++++++---
> >>>>>>>>>>>>        drivers/gpu/drm/v3d/v3d_gem.c            |  2 ++
> >>>>>>>>>>>>        include/drm/gpu_scheduler.h              |  7 +++-
> >>>>>>>>>>>>        10 files changed, 74 insertions(+), 14 deletions(-)
> >>>>>>>>>>>>
> >>>>>>>>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> >>>>>>>>>>>> index c5386d13eb4a..a4ec092af9a7 100644
> >>>>>>>>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> >>>>>>>>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> >>>>>>>>>>>> @@ -1226,6 +1226,8 @@ static int amdgpu_cs_submit(struct amdgpu_cs_parser *p,
> >>>>>>>>>>>>            if (r)
> >>>>>>>>>>>>                    goto error_unlock;
> >>>>>>>>>>>>
> >>>>>>>>>>>> +     drm_sched_job_arm(&job->base);
> >>>>>>>>>>>> +
> >>>>>>>>>>>>            /* No memory allocation is allowed while holding the notifier lock.
> >>>>>>>>>>>>             * The lock is held until amdgpu_cs_submit is finished and fence is
> >>>>>>>>>>>>             * added to BOs.
> >>>>>>>>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
> >>>>>>>>>>>> index d33e6d97cc89..5ddb955d2315 100644
> >>>>>>>>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
> >>>>>>>>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
> >>>>>>>>>>>> @@ -170,6 +170,8 @@ int amdgpu_job_submit(struct amdgpu_job *job, struct drm_sched_entity *entity,
> >>>>>>>>>>>>            if (r)
> >>>>>>>>>>>>                    return r;
> >>>>>>>>>>>>
> >>>>>>>>>>>> +     drm_sched_job_arm(&job->base);
> >>>>>>>>>>>> +
> >>>>>>>>>>>>            *f = dma_fence_get(&job->base.s_fence->finished);
> >>>>>>>>>>>>            amdgpu_job_free_resources(job);
> >>>>>>>>>>>>            drm_sched_entity_push_job(&job->base, entity);
> >>>>>>>>>>>> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_sched.c b/drivers/gpu/drm/etnaviv/etnaviv_sched.c
> >>>>>>>>>>>> index feb6da1b6ceb..05f412204118 100644
> >>>>>>>>>>>> --- a/drivers/gpu/drm/etnaviv/etnaviv_sched.c
> >>>>>>>>>>>> +++ b/drivers/gpu/drm/etnaviv/etnaviv_sched.c
> >>>>>>>>>>>> @@ -163,6 +163,8 @@ int etnaviv_sched_push_job(struct drm_sched_entity *sched_entity,
> >>>>>>>>>>>>            if (ret)
> >>>>>>>>>>>>                    goto out_unlock;
> >>>>>>>>>>>>
> >>>>>>>>>>>> +     drm_sched_job_arm(&submit->sched_job);
> >>>>>>>>>>>> +
> >>>>>>>>>>>>            submit->out_fence = dma_fence_get(&submit->sched_job.s_fence->finished);
> >>>>>>>>>>>>            submit->out_fence_id = idr_alloc_cyclic(&submit->gpu->fence_idr,
> >>>>>>>>>>>>                                                    submit->out_fence, 0,
> >>>>>>>>>>>> diff --git a/drivers/gpu/drm/lima/lima_sched.c b/drivers/gpu/drm/lima/lima_sched.c
> >>>>>>>>>>>> index dba8329937a3..38f755580507 100644
> >>>>>>>>>>>> --- a/drivers/gpu/drm/lima/lima_sched.c
> >>>>>>>>>>>> +++ b/drivers/gpu/drm/lima/lima_sched.c
> >>>>>>>>>>>> @@ -129,6 +129,8 @@ int lima_sched_task_init(struct lima_sched_task *task,
> >>>>>>>>>>>>                    return err;
> >>>>>>>>>>>>            }
> >>>>>>>>>>>>
> >>>>>>>>>>>> +     drm_sched_job_arm(&task->base);
> >>>>>>>>>>>> +
> >>>>>>>>>>>>            task->num_bos = num_bos;
> >>>>>>>>>>>>            task->vm = lima_vm_get(vm);
> >>>>>>>>>>>>
> >>>>>>>>>>>> diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
> >>>>>>>>>>>> index 71a72fb50e6b..2992dc85325f 100644
> >>>>>>>>>>>> --- a/drivers/gpu/drm/panfrost/panfrost_job.c
> >>>>>>>>>>>> +++ b/drivers/gpu/drm/panfrost/panfrost_job.c
> >>>>>>>>>>>> @@ -288,6 +288,8 @@ int panfrost_job_push(struct panfrost_job *job)
> >>>>>>>>>>>>                    goto unlock;
> >>>>>>>>>>>>            }
> >>>>>>>>>>>>
> >>>>>>>>>>>> +     drm_sched_job_arm(&job->base);
> >>>>>>>>>>>> +
> >>>>>>>>>>>>            job->render_done_fence = dma_fence_get(&job->base.s_fence->finished);
> >>>>>>>>>>>>
> >>>>>>>>>>>>            ret = panfrost_acquire_object_fences(job->bos, job->bo_count,
> >>>>>>>>>>>> diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
> >>>>>>>>>>>> index 79554aa4dbb1..f7347c284886 100644
> >>>>>>>>>>>> --- a/drivers/gpu/drm/scheduler/sched_entity.c
> >>>>>>>>>>>> +++ b/drivers/gpu/drm/scheduler/sched_entity.c
> >>>>>>>>>>>> @@ -485,9 +485,9 @@ void drm_sched_entity_select_rq(struct drm_sched_entity *entity)
> >>>>>>>>>>>>         * @sched_job: job to submit
> >>>>>>>>>>>>         * @entity: scheduler entity
> >>>>>>>>>>>>         *
> >>>>>>>>>>>> - * Note: To guarantee that the order of insertion to queue matches
> >>>>>>>>>>>> - * the job's fence sequence number this function should be
> >>>>>>>>>>>> - * called with drm_sched_job_init under common lock.
> >>>>>>>>>>>> + * Note: To guarantee that the order of insertion to queue matches the job's
> >>>>>>>>>>>> + * fence sequence number this function should be called with drm_sched_job_arm()
> >>>>>>>>>>>> + * under common lock.
> >>>>>>>>>>>>         *
> >>>>>>>>>>>>         * Returns 0 for success, negative error code otherwise.
> >>>>>>>>>>>>         */
> >>>>>>>>>>>> diff --git a/drivers/gpu/drm/scheduler/sched_fence.c b/drivers/gpu/drm/scheduler/sched_fence.c
> >>>>>>>>>>>> index 69de2c76731f..c451ee9a30d7 100644
> >>>>>>>>>>>> --- a/drivers/gpu/drm/scheduler/sched_fence.c
> >>>>>>>>>>>> +++ b/drivers/gpu/drm/scheduler/sched_fence.c
> >>>>>>>>>>>> @@ -90,7 +90,7 @@ static const char *drm_sched_fence_get_timeline_name(struct dma_fence *f)
> >>>>>>>>>>>>         *
> >>>>>>>>>>>>         * Free up the fence memory after the RCU grace period.
> >>>>>>>>>>>>         */
> >>>>>>>>>>>> -static void drm_sched_fence_free(struct rcu_head *rcu)
> >>>>>>>>>>>> +void drm_sched_fence_free(struct rcu_head *rcu)
> >>>>>>>>>>>>        {
> >>>>>>>>>>>>            struct dma_fence *f = container_of(rcu, struct dma_fence, rcu);
> >>>>>>>>>>>>            struct drm_sched_fence *fence = to_drm_sched_fence(f);
> >>>>>>>>>>>> @@ -152,11 +152,10 @@ struct drm_sched_fence *to_drm_sched_fence(struct dma_fence *f)
> >>>>>>>>>>>>        }
> >>>>>>>>>>>>        EXPORT_SYMBOL(to_drm_sched_fence);
> >>>>>>>>>>>>
> >>>>>>>>>>>> -struct drm_sched_fence *drm_sched_fence_create(struct drm_sched_entity *entity,
> >>>>>>>>>>>> -                                            void *owner)
> >>>>>>>>>>>> +struct drm_sched_fence *drm_sched_fence_alloc(struct drm_sched_entity *entity,
> >>>>>>>>>>>> +                                           void *owner)
> >>>>>>>>>>>>        {
> >>>>>>>>>>>>            struct drm_sched_fence *fence = NULL;
> >>>>>>>>>>>> -     unsigned seq;
> >>>>>>>>>>>>
> >>>>>>>>>>>>            fence = kmem_cache_zalloc(sched_fence_slab, GFP_KERNEL);
> >>>>>>>>>>>>            if (fence == NULL)
> >>>>>>>>>>>> @@ -166,13 +165,19 @@ struct drm_sched_fence *drm_sched_fence_create(struct drm_sched_entity *entity,
> >>>>>>>>>>>>            fence->sched = entity->rq->sched;
> >>>>>>>>>>>>            spin_lock_init(&fence->lock);
> >>>>>>>>>>>>
> >>>>>>>>>>>> +     return fence;
> >>>>>>>>>>>> +}
> >>>>>>>>>>>> +
> >>>>>>>>>>>> +void drm_sched_fence_init(struct drm_sched_fence *fence,
> >>>>>>>>>>>> +                       struct drm_sched_entity *entity)
> >>>>>>>>>>>> +{
> >>>>>>>>>>>> +     unsigned seq;
> >>>>>>>>>>>> +
> >>>>>>>>>>>>            seq = atomic_inc_return(&entity->fence_seq);
> >>>>>>>>>>>>            dma_fence_init(&fence->scheduled, &drm_sched_fence_ops_scheduled,
> >>>>>>>>>>>>                           &fence->lock, entity->fence_context, seq);
> >>>>>>>>>>>>            dma_fence_init(&fence->finished, &drm_sched_fence_ops_finished,
> >>>>>>>>>>>>                           &fence->lock, entity->fence_context + 1, seq);
> >>>>>>>>>>>> -
> >>>>>>>>>>>> -     return fence;
> >>>>>>>>>>>>        }
> >>>>>>>>>>>>
> >>>>>>>>>>>>        module_init(drm_sched_fence_slab_init);
> >>>>>>>>>>>> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
> >>>>>>>>>>>> index 33c414d55fab..5e84e1500c32 100644
> >>>>>>>>>>>> --- a/drivers/gpu/drm/scheduler/sched_main.c
> >>>>>>>>>>>> +++ b/drivers/gpu/drm/scheduler/sched_main.c
> >>>>>>>>>>>> @@ -48,9 +48,11 @@
> >>>>>>>>>>>>        #include <linux/wait.h>
> >>>>>>>>>>>>        #include <linux/sched.h>
> >>>>>>>>>>>>        #include <linux/completion.h>
> >>>>>>>>>>>> +#include <linux/dma-resv.h>
> >>>>>>>>>>>>        #include <uapi/linux/sched/types.h>
> >>>>>>>>>>>>
> >>>>>>>>>>>>        #include <drm/drm_print.h>
> >>>>>>>>>>>> +#include <drm/drm_gem.h>
> >>>>>>>>>>>>        #include <drm/gpu_scheduler.h>
> >>>>>>>>>>>>        #include <drm/spsc_queue.h>
> >>>>>>>>>>>>
> >>>>>>>>>>>> @@ -569,7 +571,6 @@ EXPORT_SYMBOL(drm_sched_resubmit_jobs_ext);
> >>>>>>>>>>>>
> >>>>>>>>>>>>        /**
> >>>>>>>>>>>>         * drm_sched_job_init - init a scheduler job
> >>>>>>>>>>>> - *
> >>>>>>>>>>>>         * @job: scheduler job to init
> >>>>>>>>>>>>         * @entity: scheduler entity to use
> >>>>>>>>>>>>         * @owner: job owner for debugging
> >>>>>>>>>>>> @@ -577,6 +578,9 @@ EXPORT_SYMBOL(drm_sched_resubmit_jobs_ext);
> >>>>>>>>>>>>         * Refer to drm_sched_entity_push_job() documentation
> >>>>>>>>>>>>         * for locking considerations.
> >>>>>>>>>>>>         *
> >>>>>>>>>>>> + * Drivers must make sure drm_sched_job_cleanup() if this function returns
> >>>>>>>>>>>> + * successfully, even when @job is aborted before drm_sched_job_arm() is called.
> >>>>>>>>>>>> + *
> >>>>>>>>>>>>         * Returns 0 for success, negative error code otherwise.
> >>>>>>>>>>>>         */
> >>>>>>>>>>>>        int drm_sched_job_init(struct drm_sched_job *job,
> >>>>>>>>>>>> @@ -594,7 +598,7 @@ int drm_sched_job_init(struct drm_sched_job *job,
> >>>>>>>>>>>>            job->sched = sched;
> >>>>>>>>>>>>            job->entity = entity;
> >>>>>>>>>>>>            job->s_priority = entity->rq - sched->sched_rq;
> >>>>>>>>>>>> -     job->s_fence = drm_sched_fence_create(entity, owner);
> >>>>>>>>>>>> +     job->s_fence = drm_sched_fence_alloc(entity, owner);
> >>>>>>>>>>>>            if (!job->s_fence)
> >>>>>>>>>>>>                    return -ENOMEM;
> >>>>>>>>>>>>            job->id = atomic64_inc_return(&sched->job_id_count);
> >>>>>>>>>>>> @@ -606,13 +610,47 @@ int drm_sched_job_init(struct drm_sched_job *job,
> >>>>>>>>>>>>        EXPORT_SYMBOL(drm_sched_job_init);
> >>>>>>>>>>>>
> >>>>>>>>>>>>        /**
> >>>>>>>>>>>> - * drm_sched_job_cleanup - clean up scheduler job resources
> >>>>>>>>>>>> + * drm_sched_job_arm - arm a scheduler job for execution
> >>>>>>>>>>>> + * @job: scheduler job to arm
> >>>>>>>>>>>> + *
> >>>>>>>>>>>> + * This arms a scheduler job for execution. Specifically it initializes the
> >>>>>>>>>>>> + * &drm_sched_job.s_fence of @job, so that it can be attached to struct dma_resv
> >>>>>>>>>>>> + * or other places that need to track the completion of this job.
> >>>>>>>>>>>> + *
> >>>>>>>>>>>> + * Refer to drm_sched_entity_push_job() documentation for locking
> >>>>>>>>>>>> + * considerations.
> >>>>>>>>>>>>         *
> >>>>>>>>>>>> + * This can only be called if drm_sched_job_init() succeeded.
> >>>>>>>>>>>> + */
> >>>>>>>>>>>> +void drm_sched_job_arm(struct drm_sched_job *job)
> >>>>>>>>>>>> +{
> >>>>>>>>>>>> +     drm_sched_fence_init(job->s_fence, job->entity);
> >>>>>>>>>>>> +}
> >>>>>>>>>>>> +EXPORT_SYMBOL(drm_sched_job_arm);
> >>>>>>>>>>>> +
> >>>>>>>>>>>> +/**
> >>>>>>>>>>>> + * drm_sched_job_cleanup - clean up scheduler job resources
> >>>>>>>>>>>>         * @job: scheduler job to clean up
> >>>>>>>>>>>> + *
> >>>>>>>>>>>> + * Cleans up the resources allocated with drm_sched_job_init().
> >>>>>>>>>>>> + *
> >>>>>>>>>>>> + * Drivers should call this from their error unwind code if @job is aborted
> >>>>>>>>>>>> + * before drm_sched_job_arm() is called.
> >>>>>>>>>>>> + *
> >>>>>>>>>>>> + * After that point of no return @job is committed to be executed by the
> >>>>>>>>>>>> + * scheduler, and this function should be called from the
> >>>>>>>>>>>> + * &drm_sched_backend_ops.free_job callback.
> >>>>>>>>>>>>         */
> >>>>>>>>>>>>        void drm_sched_job_cleanup(struct drm_sched_job *job)
> >>>>>>>>>>>>        {
> >>>>>>>>>>>> -     dma_fence_put(&job->s_fence->finished);
> >>>>>>>>>>>> +     if (!kref_read(&job->s_fence->finished.refcount)) {
> >>>>>>>>>>>> +             /* drm_sched_job_arm() has been called */
> >>>>>>>>>>>> +             dma_fence_put(&job->s_fence->finished);
> >>>>>>>>>>>> +     } else {
> >>>>>>>>>>>> +             /* aborted job before committing to run it */
> >>>>>>>>>>>> +             drm_sched_fence_free(&job->s_fence->finished.rcu);
> >>>>>>>>>>>> +     }
> >>>>>>>>>>>> +
> >>>>>>>>>>>>            job->s_fence = NULL;
> >>>>>>>>>>>>        }
> >>>>>>>>>>>>        EXPORT_SYMBOL(drm_sched_job_cleanup);
> >>>>>>>>>>>> diff --git a/drivers/gpu/drm/v3d/v3d_gem.c b/drivers/gpu/drm/v3d/v3d_gem.c
> >>>>>>>>>>>> index 4eb354226972..5c3a99027ecd 100644
> >>>>>>>>>>>> --- a/drivers/gpu/drm/v3d/v3d_gem.c
> >>>>>>>>>>>> +++ b/drivers/gpu/drm/v3d/v3d_gem.c
> >>>>>>>>>>>> @@ -475,6 +475,8 @@ v3d_push_job(struct v3d_file_priv *v3d_priv,
> >>>>>>>>>>>>            if (ret)
> >>>>>>>>>>>>                    return ret;
> >>>>>>>>>>>>
> >>>>>>>>>>>> +     drm_sched_job_arm(&job->base);
> >>>>>>>>>>>> +
> >>>>>>>>>>>>            job->done_fence = dma_fence_get(&job->base.s_fence->finished);
> >>>>>>>>>>>>
> >>>>>>>>>>>>            /* put by scheduler job completion */
> >>>>>>>>>>>> diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
> >>>>>>>>>>>> index 88ae7f331bb1..83afc3aa8e2f 100644
> >>>>>>>>>>>> --- a/include/drm/gpu_scheduler.h
> >>>>>>>>>>>> +++ b/include/drm/gpu_scheduler.h
> >>>>>>>>>>>> @@ -348,6 +348,7 @@ void drm_sched_fini(struct drm_gpu_scheduler *sched);
> >>>>>>>>>>>>        int drm_sched_job_init(struct drm_sched_job *job,
> >>>>>>>>>>>>                           struct drm_sched_entity *entity,
> >>>>>>>>>>>>                           void *owner);
> >>>>>>>>>>>> +void drm_sched_job_arm(struct drm_sched_job *job);
> >>>>>>>>>>>>        void drm_sched_entity_modify_sched(struct drm_sched_entity *entity,
> >>>>>>>>>>>>                                        struct drm_gpu_scheduler **sched_list,
> >>>>>>>>>>>>                                           unsigned int num_sched_list);
> >>>>>>>>>>>> @@ -387,8 +388,12 @@ void drm_sched_entity_set_priority(struct drm_sched_entity *entity,
> >>>>>>>>>>>>                                       enum drm_sched_priority priority);
> >>>>>>>>>>>>        bool drm_sched_entity_is_ready(struct drm_sched_entity *entity);
> >>>>>>>>>>>>
> >>>>>>>>>>>> -struct drm_sched_fence *drm_sched_fence_create(
> >>>>>>>>>>>> +struct drm_sched_fence *drm_sched_fence_alloc(
> >>>>>>>>>>>>            struct drm_sched_entity *s_entity, void *owner);
> >>>>>>>>>>>> +void drm_sched_fence_init(struct drm_sched_fence *fence,
> >>>>>>>>>>>> +                       struct drm_sched_entity *entity);
> >>>>>>>>>>>> +void drm_sched_fence_free(struct rcu_head *rcu);
> >>>>>>>>>>>> +
> >>>>>>>>>>>>        void drm_sched_fence_scheduled(struct drm_sched_fence *fence);
> >>>>>>>>>>>>        void drm_sched_fence_finished(struct drm_sched_fence *fence);
> >>>>>>>>>>>>
> >>>> --
> >>>> Daniel Vetter
> >>>> Software Engineer, Intel Corporation
> >>>> https://nam11.safelinks.protection.outlook.com/?url=http%3A%2F%2Fblog.ffwll.ch%2F&amp;data=04%7C01%7Cchristian.koenig%40amd.com%7C7086790381b9415f60e708d941f78266%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637613353580226578%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=9GhYoGHD6TlcrW5dvT9Z%2BFukW%2F8%2BicK2t8180coEsJY%3D&amp;reserved=0
> >>>
> >>> --
> >>> Daniel Vetter
> >>> Software Engineer, Intel Corporation
> >>> https://nam11.safelinks.protection.outlook.com/?url=http%3A%2F%2Fblog.ffwll.ch%2F&amp;data=04%7C01%7Cchristian.koenig%40amd.com%7C7086790381b9415f60e708d941f78266%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637613353580236571%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=Yt%2FirDjTmtDUjQS1xlYg4x5mz82cHkNyLPkNNpO31ro%3D&amp;reserved=0
>


-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

  reply	other threads:[~2021-07-08 11:20 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-02 21:38 [PATCH v2 00/11] drm/scheduler dependency tracking Daniel Vetter
2021-07-02 21:38 ` [PATCH v2 01/11] drm/sched: Split drm_sched_job_init Daniel Vetter
2021-07-02 21:38   ` Daniel Vetter
2021-07-07  9:29   ` Christian König
2021-07-07  9:29     ` Christian König
2021-07-07 11:14     ` Daniel Vetter
2021-07-07 11:14       ` Daniel Vetter
2021-07-07 11:57       ` Christian König
2021-07-07 11:57         ` Christian König
2021-07-07 12:13         ` Daniel Vetter
2021-07-07 12:13           ` Daniel Vetter
2021-07-07 12:58           ` Christian König
2021-07-07 12:58             ` Christian König
2021-07-07 16:32             ` Daniel Vetter
2021-07-07 16:32               ` Daniel Vetter
2021-07-08  6:56               ` Christian König
2021-07-08  6:56                 ` Christian König
2021-07-08  7:09                 ` Daniel Vetter
2021-07-08  7:09                   ` Daniel Vetter
2021-07-08  7:19                   ` Daniel Vetter
2021-07-08  7:19                     ` Daniel Vetter
2021-07-08  7:53                     ` Christian König
2021-07-08  7:53                       ` Christian König
2021-07-08 10:02                       ` Daniel Vetter
2021-07-08 10:02                         ` Daniel Vetter
2021-07-08 10:54                         ` Christian König
2021-07-08 10:54                           ` Christian König
2021-07-08 11:20                           ` Daniel Vetter [this message]
2021-07-08 11:20                             ` Daniel Vetter
2021-07-08 11:28                             ` Christian König
2021-07-08 11:28                               ` Christian König
2021-07-02 21:38 ` [PATCH v2 02/11] drm/sched: Add dependency tracking Daniel Vetter
2021-07-02 21:38   ` Daniel Vetter
2021-07-07  9:26   ` [Linaro-mm-sig] " Christian König
2021-07-07  9:26     ` Christian König
2021-07-07 11:23     ` Daniel Vetter
2021-07-07 11:23       ` Daniel Vetter
2021-07-02 21:38 ` [PATCH v2 03/11] drm/sched: drop entity parameter from drm_sched_push_job Daniel Vetter
2021-07-02 21:38   ` Daniel Vetter
2021-07-02 21:38 ` [PATCH v2 04/11] drm/panfrost: use scheduler dependency tracking Daniel Vetter
2021-07-02 21:38   ` Daniel Vetter
2021-07-02 21:38 ` [PATCH v2 05/11] drm/lima: " Daniel Vetter
2021-07-02 21:38 ` [PATCH v2 06/11] drm/v3d: Move drm_sched_job_init to v3d_job_init Daniel Vetter
2021-07-02 21:38 ` [PATCH v2 07/11] drm/v3d: Use scheduler dependency handling Daniel Vetter
2021-07-02 21:38 ` [PATCH v2 08/11] drm/etnaviv: " Daniel Vetter
2021-07-02 21:38   ` Daniel Vetter
2021-07-07  9:08   ` Lucas Stach
2021-07-07  9:08     ` Lucas Stach
2021-07-07 11:26     ` Daniel Vetter
2021-07-07 11:26       ` Daniel Vetter
2021-07-07 11:32       ` Daniel Vetter
2021-07-07 11:32         ` Daniel Vetter
2021-07-07 12:34         ` Lucas Stach
2021-07-07 12:34           ` Lucas Stach
2021-07-02 21:38 ` [PATCH v2 09/11] drm/gem: Delete gem array fencing helpers Daniel Vetter
2021-07-02 21:38   ` Daniel Vetter
2021-07-02 21:38 ` [PATCH v2 10/11] drm/sched: Don't store self-dependencies Daniel Vetter
2021-07-02 21:38 ` [PATCH v2 11/11] drm/sched: Check locking in drm_sched_job_await_implicit Daniel Vetter

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