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On 08/03/2018 10:06 AM, Christian König
wrote:
Am 02.08.2018 um 16:11 schrieb Andrey
Grodzovsky:
On 08/02/2018 02:47 AM, Nayan
Deshmukh wrote:
Am
02.08.2018 um 00:25 schrieb Andrey Grodzovsky:
> Thinking again about this change and 53d5f1e
drm/scheduler: move idle
> entities to scheduler with less load v2
>
> Looks to me like use case for which fc9a539
drm/scheduler: add NULL
> pointer check for run queue (v2) was done
>
> will not work anymore.
>
> First of all in drm_sched_entity_push_job, 'if
(!entity->rq)' will
> never be true any more since we stopped
entity->rq to NULL in
>
> drm_sched_entity_flush.
Good point, going to remove that.
So basically we don't need that if (...){ return; } in
drm_sched_entity_push_job any more ?
Yes, exactly.
>
> Second of all, even after we removed the entity
from rq in
> drm_sched_entity_flush to terminate any subsequent
submissions
>
> to the queue the other thread doing push job can
just acquire again a
> run queue
>
> from drm_sched_entity_get_free_sched and continue
submission
Hi Christian
That
is actually desired.
When another process is now using the entity to submit
jobs adding it
back to the rq is actually the right thing to do cause
the entity is
still in use.
Yes, no problem if it's another process. But what about another
thread from same process ? Is it a possible use case that 2
threads from same process submit to same entity concurrently ?
If so and we specifically kill one, the other will not stop
event if we want him to because current code makes him just
require a rq for him self.
Well you can't kill a single thread of a process (you can only
interrupt it), a SIGKILL will always kill the whole process.
Is the following scenario possible and acceptable ?
2 threads from same process working on same queue where thread A
currently in drm_sched_entity_flush->wait_event_timeout (the
process getting shut down because of SIGKILL sent by user)
while thread B still inside drm_sched_entity_push_job before 'if
(reschedule)'. 'A' stopped waiting because queue became empty and
then removes the entity queue from scheduler's run queue while
B goes inside 'reschedule' because it evaluates to true ('first' is
true and all the rest of the conditions), acquires new rq, and later
adds it back to scheduler (different one maybe) and keeps submitting
jobs as much as he likes and then can be stack for up to 'timeout'
time in his drm_sched_entity_flush waiting for them.
My understanding was that introduction of entity->last is to
force immediate termination job submissions by any thread from the
terminating process.
Andrey
I am not aware of the usecase so I might just be
rambling. but if the thread/process that created the
entity has called drm_sched_entity_flush then we
shouldn't allow other processes to push jobs to that
entity.
Nayan
Christian.
We don't really know who created the entity, the creation could
be by X itself and then it's passed to other process for use.
Check 'drm/scheduler: only kill entity if last user is killed
v2', the idea is that if by the time you want to
kill this entity another process (not another thread from your
process - i.e. current->group_leader != last_user in
drm_sched_entity_flush) already started to use this entity just
let it be.
Yes, exactly that's the idea.
Christian.
Andrey
> so you can't substitute ' if (!entity->rq)' to
'if
> (list_empty(&entity->list))'.
>
> What about adding a 'stopped' flag to
drm_sched_entity to be set in
> drm_sched_entity_flush and in
>
> drm_sched_entity_push_job check for 'if
(!entity->stopped)' instead
> of ' if (!entity->rq)' ?
>
> Andrey
>
>
> On 07/30/2018 07:03 AM, Christian König wrote:
>> We removed the redundancy of having an extra
scheduler field, so we
>> can't set the rq to NULL any more or otherwise
won't know which
>> scheduler to use for the cleanup.
>>
>> Just remove the entity from the scheduling list
instead.
>>
>> Signed-off-by: Christian König <christian.koenig@xxxxxxx>
>> ---
>> drivers/gpu/drm/scheduler/gpu_scheduler.c |
35
>> +++++++------------------------
>> 1 file changed, 8 insertions(+), 27
deletions(-)
>>
>> diff --git
a/drivers/gpu/drm/scheduler/gpu_scheduler.c
>> b/drivers/gpu/drm/scheduler/gpu_scheduler.c
>> index f563e4fbb4b6..1b733229201e 100644
>> --- a/drivers/gpu/drm/scheduler/gpu_scheduler.c
>> +++ b/drivers/gpu/drm/scheduler/gpu_scheduler.c
>> @@ -198,21 +198,6 @@ int
drm_sched_entity_init(struct
>> drm_sched_entity *entity,
>> }
>> EXPORT_SYMBOL(drm_sched_entity_init);
>> -/**
>> - * drm_sched_entity_is_initialized - Query if
entity is initialized
>> - *
>> - * @sched: Pointer to scheduler instance
>> - * @entity: The pointer to a valid scheduler
entity
>> - *
>> - * return true if entity is initialized, false
otherwise
>> -*/
>> -static bool
drm_sched_entity_is_initialized(struct drm_gpu_scheduler
>> *sched,
>> - struct
drm_sched_entity *entity)
>> -{
>> - return entity->rq != NULL &&
>> - entity->rq->sched == sched;
>> -}
>> -
>> /**
>> * drm_sched_entity_is_idle - Check if entity
is idle
>> *
>> @@ -224,7 +209,8 @@ static bool
drm_sched_entity_is_idle(struct
>> drm_sched_entity *entity)
>> {
>> rmb();
>> - if (!entity->rq ||
spsc_queue_peek(&entity->job_queue) == NULL)
>> + if (list_empty(&entity->list) ||
>> +
spsc_queue_peek(&entity->job_queue) == NULL)
>> return true;
>> return false;
>> @@ -279,8 +265,6 @@ long
drm_sched_entity_flush(struct
>> drm_sched_entity *entity, long timeout)
>> long ret = timeout;
>> sched = entity->rq->sched;
>> - if
(!drm_sched_entity_is_initialized(sched, entity))
>> - return ret;
>> /**
>> * The client will not queue more IBs
during this fini, consume
>> existing
>> * queued IBs or discard them on SIGKILL
>> @@ -299,7 +283,7 @@ long
drm_sched_entity_flush(struct
>> drm_sched_entity *entity, long timeout)
>> last_user =
cmpxchg(&entity->last_user,
current->group_leader,
>> NULL);
>> if ((!last_user || last_user ==
current->group_leader) &&
>> (current->flags & PF_EXITING)
&& (current->exit_code ==
>> SIGKILL))
>> - drm_sched_entity_set_rq(entity, NULL);
>> +
drm_sched_rq_remove_entity(entity->rq, entity);
>> return ret;
>> }
>> @@ -320,7 +304,7 @@ void
drm_sched_entity_fini(struct
>> drm_sched_entity *entity)
>> struct drm_gpu_scheduler *sched;
>> sched = entity->rq->sched;
>> - drm_sched_entity_set_rq(entity, NULL);
>> + drm_sched_rq_remove_entity(entity->rq,
entity);
>> /* Consumption of existing IBs wasn't
completed. Forcefully
>> * remove them here.
>> @@ -416,15 +400,12 @@ void
drm_sched_entity_set_rq(struct
>> drm_sched_entity *entity,
>> if (entity->rq == rq)
>> return;
>> - spin_lock(&entity->rq_lock);
>> -
>> - if (entity->rq)
>> -
drm_sched_rq_remove_entity(entity->rq, entity);
>> + BUG_ON(!rq);
>> + spin_lock(&entity->rq_lock);
>> + drm_sched_rq_remove_entity(entity->rq,
entity);
>> entity->rq = rq;
>> - if (rq)
>> - drm_sched_rq_add_entity(rq, entity);
>> -
>> + drm_sched_rq_add_entity(rq, entity);
>> spin_unlock(&entity->rq_lock);
>> }
>> EXPORT_SYMBOL(drm_sched_entity_set_rq);
>
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