Re: [PATCH v2] drm/amdkfd: don't use dqm lock during device reset/suspend/resume

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On 2019-10-22 14:28, Yang, Philip wrote:
> If device reset/suspend/resume failed for some reason, dqm lock is
> hold forever and this causes deadlock. Below is a kernel backtrace when
> application open kfd after suspend/resume failed.
>
> Instead of holding dqm lock in pre_reset and releasing dqm lock in
> post_reset, add dqm->device_stopped flag which is modified in
> dqm->ops.start and dqm->ops.stop. The flag doesn't need lock protection
> because write/read are all inside dqm lock.
>
> For HWS case, map_queues_cpsch and unmap_queues_cpsch checks
> device_stopped flag before sending the updated runlist.
>
> v2: For no-HWS case, when device is stopped, don't call
> load/destroy_mqd for eviction, restore and create queue, and avoid
> debugfs dump hdqs.
>
> Backtrace of dqm lock deadlock:
>
> [Thu Oct 17 16:43:37 2019] INFO: task rocminfo:3024 blocked for more
> than 120 seconds.
> [Thu Oct 17 16:43:37 2019]       Not tainted
> 5.0.0-rc1-kfd-compute-rocm-dkms-no-npi-1131 #1
> [Thu Oct 17 16:43:37 2019] "echo 0 >
> /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [Thu Oct 17 16:43:37 2019] rocminfo        D    0  3024   2947
> 0x80000000
> [Thu Oct 17 16:43:37 2019] Call Trace:
> [Thu Oct 17 16:43:37 2019]  ? __schedule+0x3d9/0x8a0
> [Thu Oct 17 16:43:37 2019]  schedule+0x32/0x70
> [Thu Oct 17 16:43:37 2019]  schedule_preempt_disabled+0xa/0x10
> [Thu Oct 17 16:43:37 2019]  __mutex_lock.isra.9+0x1e3/0x4e0
> [Thu Oct 17 16:43:37 2019]  ? __call_srcu+0x264/0x3b0
> [Thu Oct 17 16:43:37 2019]  ? process_termination_cpsch+0x24/0x2f0
> [amdgpu]
> [Thu Oct 17 16:43:37 2019]  process_termination_cpsch+0x24/0x2f0
> [amdgpu]
> [Thu Oct 17 16:43:37 2019]
> kfd_process_dequeue_from_all_devices+0x42/0x60 [amdgpu]
> [Thu Oct 17 16:43:37 2019]  kfd_process_notifier_release+0x1be/0x220
> [amdgpu]
> [Thu Oct 17 16:43:37 2019]  __mmu_notifier_release+0x3e/0xc0
> [Thu Oct 17 16:43:37 2019]  exit_mmap+0x160/0x1a0
> [Thu Oct 17 16:43:37 2019]  ? __handle_mm_fault+0xba3/0x1200
> [Thu Oct 17 16:43:37 2019]  ? exit_robust_list+0x5a/0x110
> [Thu Oct 17 16:43:37 2019]  mmput+0x4a/0x120
> [Thu Oct 17 16:43:37 2019]  do_exit+0x284/0xb20
> [Thu Oct 17 16:43:37 2019]  ? handle_mm_fault+0xfa/0x200
> [Thu Oct 17 16:43:37 2019]  do_group_exit+0x3a/0xa0
> [Thu Oct 17 16:43:37 2019]  __x64_sys_exit_group+0x14/0x20
> [Thu Oct 17 16:43:37 2019]  do_syscall_64+0x4f/0x100
> [Thu Oct 17 16:43:37 2019]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
>
> Suggested-by: Felix Kuehling <Felix.Kuehling@xxxxxxx>
> Signed-off-by: Philip Yang <Philip.Yang@xxxxxxx>

Three more comments inline. With those comments addressed, this patch is

Reviewed-by: Felix Kuehling <Felix.Kuehling@xxxxxxx>


> ---
>   drivers/gpu/drm/amd/amdkfd/kfd_chardev.c      |  6 +--
>   drivers/gpu/drm/amd/amdkfd/kfd_device.c       |  5 --
>   .../drm/amd/amdkfd/kfd_device_queue_manager.c | 47 +++++++++++++++++--
>   .../drm/amd/amdkfd/kfd_device_queue_manager.h |  1 +
>   4 files changed, 46 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
> index d9e36dbf13d5..40d75c39f08e 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
> @@ -120,13 +120,13 @@ static int kfd_open(struct inode *inode, struct file *filep)
>   		return -EPERM;
>   	}
>   
> +	if (kfd_is_locked())
> +		return -EAGAIN;
> +
>   	process = kfd_create_process(filep);
>   	if (IS_ERR(process))
>   		return PTR_ERR(process);
>   
> -	if (kfd_is_locked())
> -		return -EAGAIN;
> -

Is this part of the change still needed? I remember that this sequence 
was a bit tricky with some potential race condition when Shaoyun was 
working on it. This may have unintended side effects.


>   	dev_dbg(kfd_device, "process %d opened, compat mode (32 bit) - %d\n",
>   		process->pasid, process->is_32bit_user_mode);
>   
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_device.c b/drivers/gpu/drm/amd/amdkfd/kfd_device.c
> index 8f4b24e84964..4fa8834ce7cb 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_device.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_device.c
> @@ -730,9 +730,6 @@ int kgd2kfd_pre_reset(struct kfd_dev *kfd)
>   		return 0;
>   	kgd2kfd_suspend(kfd);
>   
> -	/* hold dqm->lock to prevent further execution*/
> -	dqm_lock(kfd->dqm);
> -
>   	kfd_signal_reset_event(kfd);
>   	return 0;
>   }
> @@ -750,8 +747,6 @@ int kgd2kfd_post_reset(struct kfd_dev *kfd)
>   	if (!kfd->init_complete)
>   		return 0;
>   
> -	dqm_unlock(kfd->dqm);
> -
>   	ret = kfd_resume(kfd);
>   	if (ret)
>   		return ret;
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c b/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c
> index 81fb545cf42c..82e1c6280d13 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c
> @@ -340,6 +340,10 @@ static int create_queue_nocpsch(struct device_queue_manager *dqm,
>   	mqd_mgr->init_mqd(mqd_mgr, &q->mqd, q->mqd_mem_obj,
>   				&q->gart_mqd_addr, &q->properties);
>   	if (q->properties.is_active) {
> +		if (!dqm->sched_running) {
> +			WARN_ONCE(1, "Load non-HWS mqd while stopped\n");
> +			goto add_queue_to_list;
> +		}
>   
>   		if (WARN(q->process->mm != current->mm,
>   					"should only run in user thread"))
> @@ -351,6 +355,7 @@ static int create_queue_nocpsch(struct device_queue_manager *dqm,
>   			goto out_free_mqd;
>   	}
>   
> +add_queue_to_list:
>   	list_add(&q->list, &qpd->queues_list);
>   	qpd->queue_count++;
>   	if (q->properties.is_active)
> @@ -458,6 +463,11 @@ static int destroy_queue_nocpsch_locked(struct device_queue_manager *dqm,
>   
>   	deallocate_doorbell(qpd, q);
>   
> +	if (!dqm->sched_running) {
> +		WARN_ONCE(1, "Destroy non-HWS queue while stopped\n");
> +		return 0;
> +	}
> +
>   	retval = mqd_mgr->destroy_mqd(mqd_mgr, q->mqd,
>   				KFD_PREEMPT_TYPE_WAVEFRONT_RESET,
>   				KFD_UNMAP_LATENCY_MS,
> @@ -533,6 +543,12 @@ static int update_queue(struct device_queue_manager *dqm, struct queue *q)
>   		   (q->properties.type == KFD_QUEUE_TYPE_COMPUTE ||
>   		    q->properties.type == KFD_QUEUE_TYPE_SDMA ||
>   		    q->properties.type == KFD_QUEUE_TYPE_SDMA_XGMI)) {
> +
> +		if (!dqm->sched_running) {
> +			WARN_ONCE(1, "Update non-HWS queue while stopped\n");
> +			goto out_unlock;
> +		}
> +
>   		retval = mqd_mgr->destroy_mqd(mqd_mgr, q->mqd,
>   				KFD_PREEMPT_TYPE_WAVEFRONT_DRAIN,
>   				KFD_UNMAP_LATENCY_MS, q->pipe, q->queue);
> @@ -602,6 +618,11 @@ static int evict_process_queues_nocpsch(struct device_queue_manager *dqm,
>   		mqd_mgr = dqm->mqd_mgrs[get_mqd_type_from_queue_type(
>   				q->properties.type)];
>   		q->properties.is_active = false;
> +		dqm->queue_count--;
> +
> +		if (!dqm->sched_running)
> +			continue;

Add a WARN here as well. When the scheduler is not running the queues 
should already be evicted.


> +
>   		retval = mqd_mgr->destroy_mqd(mqd_mgr, q->mqd,
>   				KFD_PREEMPT_TYPE_WAVEFRONT_DRAIN,
>   				KFD_UNMAP_LATENCY_MS, q->pipe, q->queue);
> @@ -610,7 +631,6 @@ static int evict_process_queues_nocpsch(struct device_queue_manager *dqm,
>   			 * maintain a consistent eviction state
>   			 */
>   			ret = retval;
> -		dqm->queue_count--;
>   	}
>   
>   out:
> @@ -711,6 +731,11 @@ static int restore_process_queues_nocpsch(struct device_queue_manager *dqm,
>   		mqd_mgr = dqm->mqd_mgrs[get_mqd_type_from_queue_type(
>   				q->properties.type)];
>   		q->properties.is_active = true;
> +		dqm->queue_count++;
> +
> +		if (!dqm->sched_running)
> +			continue;

Add a WARN here as well. This should not happen while we're suspended.

Regards,
   Felix

> +
>   		retval = mqd_mgr->load_mqd(mqd_mgr, q->mqd, q->pipe,
>   				       q->queue, &q->properties, mm);
>   		if (retval && !ret)
> @@ -718,7 +743,6 @@ static int restore_process_queues_nocpsch(struct device_queue_manager *dqm,
>   			 * maintain a consistent eviction state
>   			 */
>   			ret = retval;
> -		dqm->queue_count++;
>   	}
>   	qpd->evicted = 0;
>   out:
> @@ -915,7 +939,8 @@ static int start_nocpsch(struct device_queue_manager *dqm)
>   	
>   	if (dqm->dev->device_info->asic_family == CHIP_HAWAII)
>   		return pm_init(&dqm->packets, dqm);
> -	
> +	dqm->sched_running = true;
> +
>   	return 0;
>   }
>   
> @@ -923,7 +948,8 @@ static int stop_nocpsch(struct device_queue_manager *dqm)
>   {
>   	if (dqm->dev->device_info->asic_family == CHIP_HAWAII)
>   		pm_uninit(&dqm->packets);
> -	
> +	dqm->sched_running = false;
> +
>   	return 0;
>   }
>   
> @@ -1074,6 +1100,7 @@ static int start_cpsch(struct device_queue_manager *dqm)
>   	dqm_lock(dqm);
>   	/* clear hang status when driver try to start the hw scheduler */
>   	dqm->is_hws_hang = false;
> +	dqm->sched_running = true;
>   	execute_queues_cpsch(dqm, KFD_UNMAP_QUEUES_FILTER_DYNAMIC_QUEUES, 0);
>   	dqm_unlock(dqm);
>   
> @@ -1089,6 +1116,7 @@ static int stop_cpsch(struct device_queue_manager *dqm)
>   {
>   	dqm_lock(dqm);
>   	unmap_queues_cpsch(dqm, KFD_UNMAP_QUEUES_FILTER_ALL_QUEUES, 0);
> +	dqm->sched_running = false;
>   	dqm_unlock(dqm);
>   
>   	kfd_gtt_sa_free(dqm->dev, dqm->fence_mem);
> @@ -1275,9 +1303,10 @@ static int map_queues_cpsch(struct device_queue_manager *dqm)
>   {
>   	int retval;
>   
> +	if (!dqm->sched_running)
> +		return 0;
>   	if (dqm->queue_count <= 0 || dqm->processes_count <= 0)
>   		return 0;
> -
>   	if (dqm->active_runlist)
>   		return 0;
>   
> @@ -1299,6 +1328,8 @@ static int unmap_queues_cpsch(struct device_queue_manager *dqm,
>   {
>   	int retval = 0;
>   
> +	if (!dqm->sched_running)
> +		return 0;
>   	if (dqm->is_hws_hang)
>   		return -EIO;
>   	if (!dqm->active_runlist)
> @@ -1903,6 +1934,12 @@ int dqm_debugfs_hqds(struct seq_file *m, void *data)
>   	int pipe, queue;
>   	int r = 0;
>   
> +	if (!dqm->sched_running) {
> +		seq_printf(m, " Device is stopped\n");
> +
> +		return 0;
> +	}
> +
>   	r = dqm->dev->kfd2kgd->hqd_dump(dqm->dev->kgd,
>   					KFD_CIK_HIQ_PIPE, KFD_CIK_HIQ_QUEUE,
>   					&dump, &n_regs);
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.h b/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.h
> index 2eaea6b04cbe..a8c37e6da027 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.h
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.h
> @@ -201,6 +201,7 @@ struct device_queue_manager {
>   	bool			is_hws_hang;
>   	struct work_struct	hw_exception_work;
>   	struct kfd_mem_obj	hiq_sdma_mqd;
> +	bool			sched_running;
>   };
>   
>   void device_queue_manager_init_cik(
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