Re:[PATCH v5 3/6] drm/scheduler: rework job destruction

["Zhou, David(ChunMing)" <David1.Zhou-5C7GfCeVMHo@public.gmane.org>]

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This patch is to fix deadlock between fence->lock and sched->job_list_lock, right?
So I suggest to just move list_del_init(&s_job->node) from drm_sched_process_job to work thread. That will avoid deadlock described in the link.


-------- Original Message --------
Subject: Re: [PATCH v5 3/6] drm/scheduler: rework job destruction
From: "Grodzovsky, Andrey"
To: "Zhou, David(ChunMing)" ,dri-devel@lists.freedesktop.org,amd-gfx@lists.freedesktop.org,eric@anholt.net,etnaviv@lists.freedesktop.org,ckoenig.leichtzumerken@gmail.com
CC: "Kazlauskas, Nicholas" ,"Koenig, Christian"


On 4/22/19 8:48 AM, Chunming Zhou wrote:
> Hi Andrey,
>
> static void drm_sched_process_job(struct dma_fence *f, struct
> dma_fence_cb *cb)
> {
> ...
>           spin_lock_irqsave(&sched->job_list_lock, flags);
>           /* remove job from ring_mirror_list */
>           list_del_init(&s_job->node);
>           spin_unlock_irqrestore(&sched->job_list_lock, flags);
> [David] How about just remove above to worker from irq process? Any
> problem? Maybe I missed previous your discussion, but I think removing
> lock for list is a risk for future maintenance although you make sure
> thread safe currently.
>
> -David


We remove the lock exactly because of the fact that insertion and
removal to/from the list will be done form exactly one thread at ant
time now. So I am not sure I understand what you mean.

Andrey


>
> ...
>
>           schedule_work(&s_job->finish_work);
> }
>
> 在 2019/4/18 23:00, Andrey Grodzovsky 写道:
>> From: Christian König <christian.koenig@amd.com>
>>
>> We now destroy finished jobs from the worker thread to make sure that
>> we never destroy a job currently in timeout processing.
>> By this we avoid holding lock around ring mirror list in drm_sched_stop
>> which should solve a deadlock reported by a user.
>>
>> v2: Remove unused variable.
>> v4: Move guilty job free into sched code.
>> v5:
>> Move sched->hw_rq_count to drm_sched_start to account for counter
>> decrement in drm_sched_stop even when we don't call resubmit jobs
>> if guily job did signal.
>>
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=109692
>>
>> Signed-off-by: Christian König <christian.koenig@amd.com>
>> Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
>> ---
>>    drivers/gpu/drm/amd/amdgpu/amdgpu_device.c |   9 +-
>>    drivers/gpu/drm/etnaviv/etnaviv_dump.c     |   4 -
>>    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_main.c     | 159 +++++++++++++++++------------
>>    drivers/gpu/drm/v3d/v3d_sched.c            |   2 +-
>>    include/drm/gpu_scheduler.h                |   6 +-
>>    8 files changed, 102 insertions(+), 84 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>> index 7cee269..a0e165c 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>> @@ -3334,7 +3334,7 @@ static int amdgpu_device_pre_asic_reset(struct amdgpu_device *adev,
>>    if (!ring || !ring->sched.thread)
>>    continue;
>>
>> - drm_sched_stop(&ring->sched);
>> + drm_sched_stop(&ring->sched, &job->base);
>>
>>    /* after all hw jobs are reset, hw fence is meaningless, so force_completion */
>>    amdgpu_fence_driver_force_completion(ring);
>> @@ -3343,8 +3343,6 @@ static int amdgpu_device_pre_asic_reset(struct amdgpu_device *adev,
>>    if(job)
>>    drm_sched_increase_karma(&job->base);
>>
>> -
>> -
>>    if (!amdgpu_sriov_vf(adev)) {
>>
>>    if (!need_full_reset)
>> @@ -3482,8 +3480,7 @@ static int amdgpu_do_asic_reset(struct amdgpu_hive_info *hive,
>>    return r;
>>    }
>>
>> -static void amdgpu_device_post_asic_reset(struct amdgpu_device *adev,
>> -   struct amdgpu_job *job)
>> +static void amdgpu_device_post_asic_reset(struct amdgpu_device *adev)
>>    {
>>    int i;
>>
>> @@ -3623,7 +3620,7 @@ int amdgpu_device_gpu_recover(struct amdgpu_device *adev,
>>
>>    /* Post ASIC reset for all devs .*/
>>    list_for_each_entry(tmp_adev, device_list_handle, gmc.xgmi.head) {
>> - amdgpu_device_post_asic_reset(tmp_adev, tmp_adev == adev ? job : NULL);
>> + amdgpu_device_post_asic_reset(tmp_adev);
>>
>>    if (r) {
>>    /* bad news, how to tell it to userspace ? */
>> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_dump.c b/drivers/gpu/drm/etnaviv/etnaviv_dump.c
>> index 33854c9..5778d9c 100644
>> --- a/drivers/gpu/drm/etnaviv/etnaviv_dump.c
>> +++ b/drivers/gpu/drm/etnaviv/etnaviv_dump.c
>> @@ -135,13 +135,11 @@ void etnaviv_core_dump(struct etnaviv_gpu *gpu)
>>        mmu_size + gpu->buffer.size;
>>
>>    /* Add in the active command buffers */
>> - spin_lock_irqsave(&gpu->sched.job_list_lock, flags);
>>    list_for_each_entry(s_job, &gpu->sched.ring_mirror_list, node) {
>>    submit = to_etnaviv_submit(s_job);
>>    file_size += submit->cmdbuf.size;
>>    n_obj++;
>>    }
>> - spin_unlock_irqrestore(&gpu->sched.job_list_lock, flags);
>>
>>    /* Add in the active buffer objects */
>>    list_for_each_entry(vram, &gpu->mmu->mappings, mmu_node) {
>> @@ -183,14 +181,12 @@ void etnaviv_core_dump(struct etnaviv_gpu *gpu)
>>          gpu->buffer.size,
>>          etnaviv_cmdbuf_get_va(&gpu->buffer));
>>
>> - spin_lock_irqsave(&gpu->sched.job_list_lock, flags);
>>    list_for_each_entry(s_job, &gpu->sched.ring_mirror_list, node) {
>>    submit = to_etnaviv_submit(s_job);
>>    etnaviv_core_dump_mem(&iter, ETDUMP_BUF_CMD,
>>          submit->cmdbuf.vaddr, submit->cmdbuf.size,
>>          etnaviv_cmdbuf_get_va(&submit->cmdbuf));
>>    }
>> - spin_unlock_irqrestore(&gpu->sched.job_list_lock, flags);
>>
>>    /* Reserve space for the bomap */
>>    if (n_bomap_pages) {
>> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_sched.c b/drivers/gpu/drm/etnaviv/etnaviv_sched.c
>> index 6d24fea..a813c82 100644
>> --- a/drivers/gpu/drm/etnaviv/etnaviv_sched.c
>> +++ b/drivers/gpu/drm/etnaviv/etnaviv_sched.c
>> @@ -109,7 +109,7 @@ static void etnaviv_sched_timedout_job(struct drm_sched_job *sched_job)
>>    }
>>
>>    /* block scheduler */
>> - drm_sched_stop(&gpu->sched);
>> + drm_sched_stop(&gpu->sched, sched_job);
>>
>>    if(sched_job)
>>    drm_sched_increase_karma(sched_job);
>> diff --git a/drivers/gpu/drm/lima/lima_sched.c b/drivers/gpu/drm/lima/lima_sched.c
>> index 97bd9c1..df98931 100644
>> --- a/drivers/gpu/drm/lima/lima_sched.c
>> +++ b/drivers/gpu/drm/lima/lima_sched.c
>> @@ -300,7 +300,7 @@ static struct dma_fence *lima_sched_run_job(struct drm_sched_job *job)
>>    static void lima_sched_handle_error_task(struct lima_sched_pipe *pipe,
>>    struct lima_sched_task *task)
>>    {
>> - drm_sched_stop(&pipe->base);
>> + drm_sched_stop(&pipe->base, &task->base);
>>
>>    if (task)
>>    drm_sched_increase_karma(&task->base);
>> diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
>> index 0a7ed04..c6336b7 100644
>> --- a/drivers/gpu/drm/panfrost/panfrost_job.c
>> +++ b/drivers/gpu/drm/panfrost/panfrost_job.c
>> @@ -385,7 +385,7 @@ static void panfrost_job_timedout(struct drm_sched_job *sched_job)
>>    sched_job);
>>
>>    for (i = 0; i < NUM_JOB_SLOTS; i++)
>> - drm_sched_stop(&pfdev->js->queue[i].sched);
>> + drm_sched_stop(&pfdev->js->queue[i].sched, sched_job);
>>
>>    if (sched_job)
>>    drm_sched_increase_karma(sched_job);
>> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
>> index 19fc601..7816de7 100644
>> --- a/drivers/gpu/drm/scheduler/sched_main.c
>> +++ b/drivers/gpu/drm/scheduler/sched_main.c
>> @@ -265,32 +265,6 @@ void drm_sched_resume_timeout(struct drm_gpu_scheduler *sched,
>>    }
>>    EXPORT_SYMBOL(drm_sched_resume_timeout);
>>
>> -/* job_finish is called after hw fence signaled
>> - */
>> -static void drm_sched_job_finish(struct work_struct *work)
>> -{
>> - struct drm_sched_job *s_job = container_of(work, struct drm_sched_job,
>> -    finish_work);
>> - struct drm_gpu_scheduler *sched = s_job->sched;
>> - unsigned long flags;
>> -
>> - /*
>> - * Canceling the timeout without removing our job from the ring mirror
>> - * list is safe, as we will only end up in this worker if our jobs
>> - * finished fence has been signaled. So even if some another worker
>> - * manages to find this job as the next job in the list, the fence
>> - * signaled check below will prevent the timeout to be restarted.
>> - */
>> - cancel_delayed_work_sync(&sched->work_tdr);
>> -
>> - spin_lock_irqsave(&sched->job_list_lock, flags);
>> - /* queue TDR for next job */
>> - drm_sched_start_timeout(sched);
>> - spin_unlock_irqrestore(&sched->job_list_lock, flags);
>> -
>> - sched->ops->free_job(s_job);
>> -}
>> -
>>    static void drm_sched_job_begin(struct drm_sched_job *s_job)
>>    {
>>    struct drm_gpu_scheduler *sched = s_job->sched;
>> @@ -315,6 +289,13 @@ static void drm_sched_job_timedout(struct work_struct *work)
>>    if (job)
>>    job->sched->ops->timedout_job(job);
>>
>> + /*
>> + * Guilty job did complete and hence needs to be manually removed
>> + * See drm_sched_stop doc.
>> + */
>> + if (list_empty(&job->node))
>> + job->sched->ops->free_job(job);
>> +
>>    spin_lock_irqsave(&sched->job_list_lock, flags);
>>    drm_sched_start_timeout(sched);
>>    spin_unlock_irqrestore(&sched->job_list_lock, flags);
>> @@ -371,23 +352,26 @@ EXPORT_SYMBOL(drm_sched_increase_karma);
>>     * @sched: scheduler instance
>>     * @bad: bad scheduler job
>>     *
>> + * Stop the scheduler and also removes and frees all completed jobs.
>> + * Note: bad job will not be freed as it might be used later and so it's
>> + * callers responsibility to release it manually if it's not part of the
>> + * mirror list any more.
>> + *
>>     */
>> -void drm_sched_stop(struct drm_gpu_scheduler *sched)
>> +void drm_sched_stop(struct drm_gpu_scheduler *sched, struct drm_sched_job *bad)
>>    {
>> - struct drm_sched_job *s_job;
>> + struct drm_sched_job *s_job, *tmp;
>>    unsigned long flags;
>> - struct dma_fence *last_fence =  NULL;
>>
>>    kthread_park(sched->thread);
>>
>>    /*
>> - * Verify all the signaled jobs in mirror list are removed from the ring
>> - * by waiting for the latest job to enter the list. This should insure that
>> - * also all the previous jobs that were in flight also already singaled
>> - * and removed from the list.
>> + * Iterate the job list from later to  earlier one and either deactive
>> + * their HW callbacks or remove them from mirror list if they already
>> + * signaled.
>> + * This iteration is thread safe as sched thread is stopped.
>>    */
>> - spin_lock_irqsave(&sched->job_list_lock, flags);
>> - list_for_each_entry_reverse(s_job, &sched->ring_mirror_list, node) {
>> + list_for_each_entry_safe_reverse(s_job, tmp, &sched->ring_mirror_list, node) {
>>    if (s_job->s_fence->parent &&
>>        dma_fence_remove_callback(s_job->s_fence->parent,
>>          &s_job->cb)) {
>> @@ -395,16 +379,30 @@ void drm_sched_stop(struct drm_gpu_scheduler *sched)
>>    s_job->s_fence->parent = NULL;
>>    atomic_dec(&sched->hw_rq_count);
>>    } else {
>> - last_fence = dma_fence_get(&s_job->s_fence->finished);
>> - break;
>> + /*
>> + * remove job from ring_mirror_list.
>> + * Locking here is for concurrent resume timeout
>> + */
>> + spin_lock_irqsave(&sched->job_list_lock, flags);
>> + list_del_init(&s_job->node);
>> + spin_unlock_irqrestore(&sched->job_list_lock, flags);
>> +
>> + /*
>> + * Wait for job's HW fence callback to finish using s_job
>> + * before releasing it.
>> + *
>> + * Job is still alive so fence refcount at least 1
>> + */
>> + dma_fence_wait(&s_job->s_fence->finished, false);
>> +
>> + /*
>> + * We must keep bad job alive for later use during
>> + * recovery by some of the drivers
>> + */
>> + if (bad != s_job)
>> + sched->ops->free_job(s_job);
>>    }
>>    }
>> - spin_unlock_irqrestore(&sched->job_list_lock, flags);
>> -
>> - if (last_fence) {
>> - dma_fence_wait(last_fence, false);
>> - dma_fence_put(last_fence);
>> - }
>>    }
>>
>>    EXPORT_SYMBOL(drm_sched_stop);
>> @@ -418,21 +416,22 @@ EXPORT_SYMBOL(drm_sched_stop);
>>    void drm_sched_start(struct drm_gpu_scheduler *sched, bool full_recovery)
>>    {
>>    struct drm_sched_job *s_job, *tmp;
>> + unsigned long flags;
>>    int r;
>>
>> - if (!full_recovery)
>> - goto unpark;
>> -
>>    /*
>>    * Locking the list is not required here as the sched thread is parked
>> - * so no new jobs are being pushed in to HW and in drm_sched_stop we
>> - * flushed all the jobs who were still in mirror list but who already
>> - * signaled and removed them self from the list. Also concurrent
>> + * so no new jobs are being inserted or removed. Also concurrent
>>    * GPU recovers can't run in parallel.
>>    */
>>    list_for_each_entry_safe(s_job, tmp, &sched->ring_mirror_list, node) {
>>    struct dma_fence *fence = s_job->s_fence->parent;
>>
>> + atomic_inc(&sched->hw_rq_count);
>> +
>> + if (!full_recovery)
>> + continue;
>> +
>>    if (fence) {
>>    r = dma_fence_add_callback(fence, &s_job->cb,
>>       drm_sched_process_job);
>> @@ -445,9 +444,12 @@ void drm_sched_start(struct drm_gpu_scheduler *sched, bool full_recovery)
>>    drm_sched_process_job(NULL, &s_job->cb);
>>    }
>>
>> - drm_sched_start_timeout(sched);
>> + if (full_recovery) {
>> + spin_lock_irqsave(&sched->job_list_lock, flags);
>> + drm_sched_start_timeout(sched);
>> + spin_unlock_irqrestore(&sched->job_list_lock, flags);
>> + }
>>
>> -unpark:
>>    kthread_unpark(sched->thread);
>>    }
>>    EXPORT_SYMBOL(drm_sched_start);
>> @@ -464,7 +466,6 @@ void drm_sched_resubmit_jobs(struct drm_gpu_scheduler *sched)
>>    uint64_t guilty_context;
>>    bool found_guilty = false;
>>
>> - /*TODO DO we need spinlock here ? */
>>    list_for_each_entry_safe(s_job, tmp, &sched->ring_mirror_list, node) {
>>    struct drm_sched_fence *s_fence = s_job->s_fence;
>>
>> @@ -477,7 +478,6 @@ void drm_sched_resubmit_jobs(struct drm_gpu_scheduler *sched)
>>    dma_fence_set_error(&s_fence->finished, -ECANCELED);
>>
>>    s_job->s_fence->parent = sched->ops->run_job(s_job);
>> - atomic_inc(&sched->hw_rq_count);
>>    }
>>    }
>>    EXPORT_SYMBOL(drm_sched_resubmit_jobs);
>> @@ -514,7 +514,6 @@ int drm_sched_job_init(struct drm_sched_job *job,
>>    return -ENOMEM;
>>    job->id = atomic64_inc_return(&sched->job_id_count);
>>
>> - INIT_WORK(&job->finish_work, drm_sched_job_finish);
>>    INIT_LIST_HEAD(&job->node);
>>
>>    return 0;
>> @@ -597,24 +596,53 @@ static void drm_sched_process_job(struct dma_fence *f, struct dma_fence_cb *cb)
>>    struct drm_sched_job *s_job = container_of(cb, struct drm_sched_job, cb);
>>    struct drm_sched_fence *s_fence = s_job->s_fence;
>>    struct drm_gpu_scheduler *sched = s_fence->sched;
>> - unsigned long flags;
>> -
>> - cancel_delayed_work(&sched->work_tdr);
>>
>>    atomic_dec(&sched->hw_rq_count);
>>    atomic_dec(&sched->num_jobs);
>>
>> - spin_lock_irqsave(&sched->job_list_lock, flags);
>> - /* remove job from ring_mirror_list */
>> - list_del_init(&s_job->node);
>> - spin_unlock_irqrestore(&sched->job_list_lock, flags);
>> + trace_drm_sched_process_job(s_fence);
>>
>>    drm_sched_fence_finished(s_fence);
>> -
>> - trace_drm_sched_process_job(s_fence);
>>    wake_up_interruptible(&sched->wake_up_worker);
>> +}
>> +
>> +/**
>> + * drm_sched_cleanup_jobs - destroy finished jobs
>> + *
>> + * @sched: scheduler instance
>> + *
>> + * Remove all finished jobs from the mirror list and destroy them.
>> + */
>> +static void drm_sched_cleanup_jobs(struct drm_gpu_scheduler *sched)
>> +{
>> + unsigned long flags;
>> +
>> + /* Don't destroy jobs while the timeout worker is running */
>> + if (!cancel_delayed_work(&sched->work_tdr))
>> + return;
>> +
>> +
>> + while (!list_empty(&sched->ring_mirror_list)) {
>> + struct drm_sched_job *job;
>> +
>> + job = list_first_entry(&sched->ring_mirror_list,
>> +        struct drm_sched_job, node);
>> + if (!dma_fence_is_signaled(&job->s_fence->finished))
>> + break;
>> +
>> + spin_lock_irqsave(&sched->job_list_lock, flags);
>> + /* remove job from ring_mirror_list */
>> + list_del_init(&job->node);
>> + spin_unlock_irqrestore(&sched->job_list_lock, flags);
>> +
>> + sched->ops->free_job(job);
>> + }
>> +
>> + /* queue timeout for next job */
>> + spin_lock_irqsave(&sched->job_list_lock, flags);
>> + drm_sched_start_timeout(sched);
>> + spin_unlock_irqrestore(&sched->job_list_lock, flags);
>>
>> - schedule_work(&s_job->finish_work);
>>    }
>>
>>    /**
>> @@ -656,9 +684,10 @@ static int drm_sched_main(void *param)
>>    struct dma_fence *fence;
>>
>>    wait_event_interruptible(sched->wake_up_worker,
>> + (drm_sched_cleanup_jobs(sched),
>>    (!drm_sched_blocked(sched) &&
>>      (entity = drm_sched_select_entity(sched))) ||
>> - kthread_should_stop());
>> + kthread_should_stop()));
>>
>>    if (!entity)
>>    continue;
>> diff --git a/drivers/gpu/drm/v3d/v3d_sched.c b/drivers/gpu/drm/v3d/v3d_sched.c
>> index e740f3b..1a4abe7 100644
>> --- a/drivers/gpu/drm/v3d/v3d_sched.c
>> +++ b/drivers/gpu/drm/v3d/v3d_sched.c
>> @@ -232,7 +232,7 @@ v3d_gpu_reset_for_timeout(struct v3d_dev *v3d, struct drm_sched_job *sched_job)
>>
>>    /* block scheduler */
>>    for (q = 0; q < V3D_MAX_QUEUES; q++)
>> - drm_sched_stop(&v3d->queue[q].sched);
>> + drm_sched_stop(&v3d->queue[q].sched, sched_job);
>>
>>    if (sched_job)
>>    drm_sched_increase_karma(sched_job);
>> diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
>> index 0daca4d..9ee0f27 100644
>> --- a/include/drm/gpu_scheduler.h
>> +++ b/include/drm/gpu_scheduler.h
>> @@ -167,9 +167,6 @@ struct drm_sched_fence *to_drm_sched_fence(struct dma_fence *f);
>>     * @sched: the scheduler instance on which this job is scheduled.
>>     * @s_fence: contains the fences for the scheduling of job.
>>     * @finish_cb: the callback for the finished fence.
>> - * @finish_work: schedules the function @drm_sched_job_finish once the job has
>> - *               finished to remove the job from the
>> - *               @drm_gpu_scheduler.ring_mirror_list.
>>     * @node: used to append this struct to the @drm_gpu_scheduler.ring_mirror_list.
>>     * @id: a unique id assigned to each job scheduled on the scheduler.
>>     * @karma: increment on every hang caused by this job. If this exceeds the hang
>> @@ -188,7 +185,6 @@ struct drm_sched_job {
>>    struct drm_gpu_scheduler *sched;
>>    struct drm_sched_fence *s_fence;
>>    struct dma_fence_cb finish_cb;
>> - struct work_struct finish_work;
>>    struct list_head node;
>>    uint64_t id;
>>    atomic_t karma;
>> @@ -296,7 +292,7 @@ int drm_sched_job_init(struct drm_sched_job *job,
>>           void *owner);
>>    void drm_sched_job_cleanup(struct drm_sched_job *job);
>>    void drm_sched_wakeup(struct drm_gpu_scheduler *sched);
>> -void drm_sched_stop(struct drm_gpu_scheduler *sched);
>> +void drm_sched_stop(struct drm_gpu_scheduler *sched, struct drm_sched_job *bad);
>>    void drm_sched_start(struct drm_gpu_scheduler *sched, bool full_recovery);
>>    void drm_sched_resubmit_jobs(struct drm_gpu_scheduler *sched);
>>    void drm_sched_increase_karma(struct drm_sched_job *bad);
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