[PATCH 2/2] drm/amdgpu/display: buffer INTERRUPT_LOW_IRQ_CONTEXT interrupt work
Chen, Xiaogang
Xiaogang.Chen at amd.com
Fri Jan 15 07:21:37 UTC 2021
On 1/14/2021 1:24 AM, Grodzovsky, Andrey wrote:
>
>
> On 1/14/21 12:11 AM, Chen, Xiaogang wrote:
>> On 1/12/2021 10:54 PM, Grodzovsky, Andrey wrote:
>>>
>>> On 1/4/21 1:01 AM, Xiaogang.Chen wrote:
>>>> From: Xiaogang Chen <xiaogang.chen at amd.com>
>>>>
>>>> amdgpu DM handles INTERRUPT_LOW_IRQ_CONTEXT interrupt(hpd, hpd_rx) by
>>>> using work queue and uses single work_struct. If previous interrupt
>>>> has not been handled new interrupts(same type) will be discarded and
>>>> driver just sends "amdgpu_dm_irq_schedule_work FAILED" message out.
>>>> If some important hpd, hpd_rx related interrupts are missed by driver
>>>> the hot (un)plug devices may cause system hang or unstable, such as
>>>> system resumes from S3 sleep with mst device connected.
>>>>
>>>> This patch dynamically allocates new amdgpu_dm_irq_handler_data for
>>>> new interrupts if previous INTERRUPT_LOW_IRQ_CONTEXT interrupt work
>>>> has not been handled. So the new interrupt works can be queued to the
>>>> same workqueue_struct, instead discard the new interrupts.
>>>> All allocated amdgpu_dm_irq_handler_data are put into a single linked
>>>> list and will be reused after.
>>>
>>>
>>> I believe this creates a possible concurrency between already
>>> executing work item
>>> and the new incoming one for which you allocate a new work item on
>>> the fly. While
>>> handle_hpd_irq is serialized with aconnector->hpd_lock I am seeing
>>> that for handle_hpd_rx_irq
>>> it's not locked for MST use case (which is the most frequently used
>>> with this interrupt). Did you
>>> verified that handle_hpd_rx_irq is reentrant ?
>>>
>> handle_hpd_rx_irq is put at a work queue. Its execution is serialized
>> by the work queue. So there is no reentrant.
>>
> You are using system_highpri_wq which has the property that it has
> multiple workers thread pool spread across all the
> active CPUs, see all work queue definitions here
> https://elixir.bootlin.com/linux/v5.11-rc3/source/include/linux/workqueue.h#L358
> I beleieve that what you saying about no chance of reentrnacy would be
> correct if it would be same work item dequeued for execution
> while previous instance is still running, see the explanation here -
> https://elixir.bootlin.com/linux/v5.11-rc3/source/kernel/workqueue.c#L1435.
> Non reentrancy is guaranteed only for the same work item. If you want
> non reentrancy (full serializtion) for different work items you should
> create
> you own single threaded work-queue using create_singlethread_workqueue
>
>
Thank you. I think the easiest way is using aconnector->hpd_lock at
handle_hpd_rx_irq to lock for dc_link->type == dc_connection_mst_branch
case, right? I will do that at next version if you think it is ok.
>> amdgpu_dm_irq_schedule_work does queuing of work(put
>> handle_hpd_rx_irq into work queue). The first call is
>> dm_irq_work_func, then call handle_hpd_rx_irq.
>>>
>>>>
>>>> Signed-off-by: Xiaogang Chen <xiaogang.chen at amd.com>
>>>> ---
>>>> drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h | 14 +--
>>>> .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_irq.c | 114
>>>> ++++++++++++++-------
>>>> 2 files changed, 80 insertions(+), 48 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
>>>> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
>>>> index c9d82b9..730e540 100644
>>>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
>>>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
>>>> @@ -69,18 +69,6 @@ struct common_irq_params {
>>>> };
>>>> /**
>>>> - * struct irq_list_head - Linked-list for low context IRQ handlers.
>>>> - *
>>>> - * @head: The list_head within &struct handler_data
>>>> - * @work: A work_struct containing the deferred handler work
>>>> - */
>>>> -struct irq_list_head {
>>>> - struct list_head head;
>>>> - /* In case this interrupt needs post-processing, 'work' will
>>>> be queued*/
>>>> - struct work_struct work;
>>>> -};
>>>> -
>>>> -/**
>>>> * struct dm_compressor_info - Buffer info used by frame buffer
>>>> compression
>>>> * @cpu_addr: MMIO cpu addr
>>>> * @bo_ptr: Pointer to the buffer object
>>>> @@ -270,7 +258,7 @@ struct amdgpu_display_manager {
>>>> * Note that handlers are called in the same order as they were
>>>> * registered (FIFO).
>>>> */
>>>> - struct irq_list_head
>>>> irq_handler_list_low_tab[DAL_IRQ_SOURCES_NUMBER];
>>>> + struct list_head
>>>> irq_handler_list_low_tab[DAL_IRQ_SOURCES_NUMBER];
>>>> /**
>>>> * @irq_handler_list_high_tab:
>>>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_irq.c
>>>> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_irq.c
>>>> index 3577785..ada344a 100644
>>>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_irq.c
>>>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_irq.c
>>>> @@ -82,6 +82,7 @@ struct amdgpu_dm_irq_handler_data {
>>>> struct amdgpu_display_manager *dm;
>>>> /* DAL irq source which registered for this interrupt. */
>>>> enum dc_irq_source irq_source;
>>>> + struct work_struct work;
>>>> };
>>>> #define DM_IRQ_TABLE_LOCK(adev, flags) \
>>>> @@ -111,20 +112,10 @@ static void init_handler_common_data(struct
>>>> amdgpu_dm_irq_handler_data *hcd,
>>>> */
>>>> static void dm_irq_work_func(struct work_struct *work)
>>>> {
>>>> - struct irq_list_head *irq_list_head =
>>>> - container_of(work, struct irq_list_head, work);
>>>> - struct list_head *handler_list = &irq_list_head->head;
>>>> - struct amdgpu_dm_irq_handler_data *handler_data;
>>>> -
>>>> - list_for_each_entry(handler_data, handler_list, list) {
>>>> - DRM_DEBUG_KMS("DM_IRQ: work_func: for dal_src=%d\n",
>>>> - handler_data->irq_source);
>>>> + struct amdgpu_dm_irq_handler_data *handler_data =
>>>> + container_of(work, struct amdgpu_dm_irq_handler_data, work);
>>>> - DRM_DEBUG_KMS("DM_IRQ: schedule_work: for dal_src=%d\n",
>>>> - handler_data->irq_source);
>>>> -
>>>> - handler_data->handler(handler_data->handler_arg);
>>>> - }
>>>> + handler_data->handler(handler_data->handler_arg);
>>>> /* Call a DAL subcomponent which registered for interrupt
>>>> notification
>>>> * at INTERRUPT_LOW_IRQ_CONTEXT.
>>>> @@ -156,7 +147,7 @@ static struct list_head
>>>> *remove_irq_handler(struct amdgpu_device *adev,
>>>> break;
>>>> case INTERRUPT_LOW_IRQ_CONTEXT:
>>>> default:
>>>> - hnd_list =
>>>> &adev->dm.irq_handler_list_low_tab[irq_source].head;
>>>> + hnd_list = &adev->dm.irq_handler_list_low_tab[irq_source];
>>>> break;
>>>> }
>>>> @@ -287,7 +278,8 @@ void *amdgpu_dm_irq_register_interrupt(struct
>>>> amdgpu_device *adev,
>>>> break;
>>>> case INTERRUPT_LOW_IRQ_CONTEXT:
>>>> default:
>>>> - hnd_list =
>>>> &adev->dm.irq_handler_list_low_tab[irq_source].head;
>>>> + hnd_list = &adev->dm.irq_handler_list_low_tab[irq_source];
>>>> + INIT_WORK(&handler_data->work, dm_irq_work_func);
>>>> break;
>>>> }
>>>> @@ -369,7 +361,7 @@ void
>>>> amdgpu_dm_irq_unregister_interrupt(struct amdgpu_device *adev,
>>>> int amdgpu_dm_irq_init(struct amdgpu_device *adev)
>>>> {
>>>> int src;
>>>> - struct irq_list_head *lh;
>>>> + struct list_head *lh;
>>>> DRM_DEBUG_KMS("DM_IRQ\n");
>>>> @@ -378,9 +370,7 @@ int amdgpu_dm_irq_init(struct amdgpu_device
>>>> *adev)
>>>> for (src = 0; src < DAL_IRQ_SOURCES_NUMBER; src++) {
>>>> /* low context handler list init */
>>>> lh = &adev->dm.irq_handler_list_low_tab[src];
>>>> - INIT_LIST_HEAD(&lh->head);
>>>> - INIT_WORK(&lh->work, dm_irq_work_func);
>>>> -
>>>> + INIT_LIST_HEAD(lh);
>>>> /* high context handler init */
>>>> INIT_LIST_HEAD(&adev->dm.irq_handler_list_high_tab[src]);
>>>> }
>>>> @@ -397,8 +387,11 @@ int amdgpu_dm_irq_init(struct amdgpu_device
>>>> *adev)
>>>> void amdgpu_dm_irq_fini(struct amdgpu_device *adev)
>>>> {
>>>> int src;
>>>> - struct irq_list_head *lh;
>>>> + struct list_head *lh;
>>>> + struct list_head *entry, *tmp;
>>>> + struct amdgpu_dm_irq_handler_data *handler;
>>>> unsigned long irq_table_flags;
>>>> +
>>>> DRM_DEBUG_KMS("DM_IRQ: releasing resources.\n");
>>>> for (src = 0; src < DAL_IRQ_SOURCES_NUMBER; src++) {
>>>> DM_IRQ_TABLE_LOCK(adev, irq_table_flags);
>>>> @@ -407,7 +400,15 @@ void amdgpu_dm_irq_fini(struct amdgpu_device
>>>> *adev)
>>>> * (because no code can schedule a new one). */
>>>> lh = &adev->dm.irq_handler_list_low_tab[src];
>>>> DM_IRQ_TABLE_UNLOCK(adev, irq_table_flags);
>>>> - flush_work(&lh->work);
>>>> +
>>>> + if (!list_empty(lh)) {
>>>> + list_for_each_safe(entry, tmp, lh) {
>>>> +
>>>> + handler = list_entry(entry, struct
>>>> amdgpu_dm_irq_handler_data,
>>>> + list);
>>>> + flush_work(&handler->work);
>>>> + }
>>>> + }
>>>> }
>>>> }
>>>> @@ -417,6 +418,8 @@ int amdgpu_dm_irq_suspend(struct
>>>> amdgpu_device *adev)
>>>> struct list_head *hnd_list_h;
>>>> struct list_head *hnd_list_l;
>>>> unsigned long irq_table_flags;
>>>> + struct list_head *entry, *tmp;
>>>> + struct amdgpu_dm_irq_handler_data *handler;
>>>> DM_IRQ_TABLE_LOCK(adev, irq_table_flags);
>>>> @@ -427,14 +430,22 @@ int amdgpu_dm_irq_suspend(struct
>>>> amdgpu_device *adev)
>>>> * will be disabled from manage_dm_interrupts on disable CRTC.
>>>> */
>>>> for (src = DC_IRQ_SOURCE_HPD1; src <= DC_IRQ_SOURCE_HPD6RX;
>>>> src++) {
>>>> - hnd_list_l = &adev->dm.irq_handler_list_low_tab[src].head;
>>>> + hnd_list_l = &adev->dm.irq_handler_list_low_tab[src];
>>>> hnd_list_h = &adev->dm.irq_handler_list_high_tab[src];
>>>> if (!list_empty(hnd_list_l) || !list_empty(hnd_list_h))
>>>> dc_interrupt_set(adev->dm.dc, src, false);
>>>> DM_IRQ_TABLE_UNLOCK(adev, irq_table_flags);
>>>> - flush_work(&adev->dm.irq_handler_list_low_tab[src].work);
>>>> + if (!list_empty(hnd_list_l)) {
>>>> +
>>>> + list_for_each_safe(entry, tmp, hnd_list_l) {
>>>> +
>>>> + handler = list_entry(entry, struct
>>>> amdgpu_dm_irq_handler_data,
>>>> + list);
>>>> + flush_work(&handler->work);
>>>> + }
>>>> + }
>>>> DM_IRQ_TABLE_LOCK(adev, irq_table_flags);
>>>> }
>>>> @@ -454,7 +465,7 @@ int amdgpu_dm_irq_resume_early(struct
>>>> amdgpu_device *adev)
>>>> /* re-enable short pulse interrupts HW interrupt */
>>>> for (src = DC_IRQ_SOURCE_HPD1RX; src <= DC_IRQ_SOURCE_HPD6RX;
>>>> src++) {
>>>> - hnd_list_l = &adev->dm.irq_handler_list_low_tab[src].head;
>>>> + hnd_list_l = &adev->dm.irq_handler_list_low_tab[src];
>>>> hnd_list_h = &adev->dm.irq_handler_list_high_tab[src];
>>>> if (!list_empty(hnd_list_l) || !list_empty(hnd_list_h))
>>>> dc_interrupt_set(adev->dm.dc, src, true);
>>>> @@ -480,7 +491,7 @@ int amdgpu_dm_irq_resume_late(struct
>>>> amdgpu_device *adev)
>>>> * will be enabled from manage_dm_interrupts on enable CRTC.
>>>> */
>>>> for (src = DC_IRQ_SOURCE_HPD1; src <= DC_IRQ_SOURCE_HPD6;
>>>> src++) {
>>>> - hnd_list_l = &adev->dm.irq_handler_list_low_tab[src].head;
>>>> + hnd_list_l = &adev->dm.irq_handler_list_low_tab[src];
>>>> hnd_list_h = &adev->dm.irq_handler_list_high_tab[src];
>>>> if (!list_empty(hnd_list_l) || !list_empty(hnd_list_h))
>>>> dc_interrupt_set(adev->dm.dc, src, true);
>>>> @@ -497,20 +508,53 @@ int amdgpu_dm_irq_resume_late(struct
>>>> amdgpu_device *adev)
>>>> static void amdgpu_dm_irq_schedule_work(struct amdgpu_device *adev,
>>>> enum dc_irq_source irq_source)
>>>> {
>>>> - unsigned long irq_table_flags;
>>>> - struct work_struct *work = NULL;
>>>> - DM_IRQ_TABLE_LOCK(adev, irq_table_flags);
>>>> + struct list_head *handler_list =
>>>> &adev->dm.irq_handler_list_low_tab[irq_source];
>>>> + struct amdgpu_dm_irq_handler_data *handler_data;
>>>> + bool work_queued = false;
>>>> - if
>>>> (!list_empty(&adev->dm.irq_handler_list_low_tab[irq_source].head))
>>>> - work = &adev->dm.irq_handler_list_low_tab[irq_source].work;
>>>> + if (list_empty(handler_list))
>>>> + return;
>>>> - DM_IRQ_TABLE_UNLOCK(adev, irq_table_flags);
>>>> + list_for_each_entry(handler_data, handler_list, list) {
>>>> +
>>>> + if (!queue_work(system_highpri_wq, &handler_data->work)) {
>>>> + continue;
>>>> + } else {
>>>> + work_queued = true;
>>>> + break;
>>>> + }
>>>> + }
>>>> +
>>>> + if (!work_queued) {
>>>> +
>>>> + struct amdgpu_dm_irq_handler_data *handler_data_add;
>>>> + /*get the amdgpu_dm_irq_handler_data of first item pointed
>>>> by handler_list*/
>>>> + handler_data = container_of(handler_list->next, struct
>>>> amdgpu_dm_irq_handler_data, list);
>>>> +
>>>> + /*allocate a new amdgpu_dm_irq_handler_data*/
>>>> + handler_data_add = kzalloc(sizeof(*handler_data),
>>>> GFP_KERNEL);
>>>> + if (!handler_data_add) {
>>>> + DRM_ERROR("DM_IRQ: failed to allocate irq handler!\n");
>>>> + return;
>>>> + }
>>>> +
>>>> + /*copy new amdgpu_dm_irq_handler_data members from
>>>> handler_data*/
>>>> + handler_data_add->handler = handler_data->handler;
>>>> + handler_data_add->handler_arg = handler_data->handler_arg;
>>>> + handler_data_add->dm = handler_data->dm;
>>>> + handler_data_add->irq_source = irq_source;
>>>> +
>>>> + list_add_tail(&handler_data_add->list, handler_list);
>>>
>>>
>>> At what place are you deleting completed work items from the
>>> handler_list ?
>>>
>>> Andrey
>>>
>> The new allocated work item handler_data_add is put at end of single
>> list handler_list. It is not deleted, but put into this list. In the
>> future for same interrupt source handling the previous allocated work
>> items can be reused. So we do not have to reallocate new work items
>> if previous interrupts have not been handled by cpu. On other side
>> system will keep all the allocated work items at run time. Note, the
>> new work item allocation only happens when cpu has not handled
>> previous interrupts yet, and new same type interrupts have came.
>>
>> Thanks
>>
>> Xiaogang
>>
>
> I am still confused, how you avoid executing a second time a handler
> you previously allocated because first queue_work failed,
> you always start iteration from beginning of the list and you never
> remove already successfully executed handlers.
>
> Andrey
>
>
Not sure if understand your question. If the first time queuing work
item success there is no second time queuing the same work item. The
second work item is a different one although they use same
handle_hpd_rx_irq. The queued work items are managed by work
queue(queue_work). Work queue knows each queued work item status: still
on queue, running, or exist. I look from already allocated work items to
see if work queue allows me to queue, until find one. If all allocated
work items cannot be queued, allocate a new work item and put it at the
list of allocated work items.
Thanks
Xiaogang
>>>
>>>> +
>>>> + INIT_WORK(&handler_data_add->work, dm_irq_work_func);
>>>> - if (work) {
>>>> - if (!schedule_work(work))
>>>> - DRM_INFO("amdgpu_dm_irq_schedule_work FAILED src %d\n",
>>>> - irq_source);
>>>> + if (queue_work(system_highpri_wq, &handler_data_add->work))
>>>> + DRM_DEBUG("__func__: a work_struct is allocated and
>>>> queued, "
>>>> + "src %d\n", irq_source);
>>>> + else
>>>> + DRM_ERROR("__func__: a new work_struct cannot be
>>>> queued, "
>>>> + "something is wrong, src %d\n", irq_source);
>>>> }
>>>> }
>>
>>
More information about the dri-devel
mailing list