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drm/sched: improve docs around drm_sched_entity

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I found a few too many things that are tricky and not documented, so I
started typing.

I found a few more things that looked broken while typing, see the
varios FIXME in drm_sched_entity.

Also some of the usual logics:
- actually include sched_entity.c declarations, that was lost in the
  move here: 620e762f9a ("drm/scheduler: move entity handling into
  separate file")

- Ditch the kerneldoc for internal functions, keep the comments where
  they're describing more than what the function name already implies.

- Switch drm_sched_entity to inline docs.

Acked-by: Melissa Wen <mwen@igalia.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com> (v1)
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: Boris Brezillon <boris.brezillon@collabora.com>
Cc: Steven Price <steven.price@arm.com>
Cc: Emma Anholt <emma@anholt.net>
Cc: Lee Jones <lee.jones@linaro.org>
Cc: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210805104705.862416-7-daniel.vetter@ffwll.ch
This commit is contained in:
Daniel Vetter 2021-08-05 12:46:51 +02:00
parent 0e10e9a1db
commit 981b04d968
3 changed files with 146 additions and 87 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
Documentation/gpu/drm-mm.rst
View File

@ -504,3 +504,6 @@ Scheduler Function References
.. kernel-doc:: drivers/gpu/drm/scheduler/sched_main.c
:export:
.. kernel-doc:: drivers/gpu/drm/scheduler/sched_entity.c
:export:

85
drivers/gpu/drm/scheduler/sched_entity.c
View File

@ -45,8 +45,14 @@
* @guilty: atomic_t set to 1 when a job on this queue
* is found to be guilty causing a timeout
*
* Note: the sched_list should have at least one element to schedule
* the entity
* Note that the &sched_list must have at least one element to schedule the entity.
*
* For changing @priority later on at runtime see
* drm_sched_entity_set_priority(). For changing the set of schedulers
* @sched_list at runtime see drm_sched_entity_modify_sched().
*
* An entity is cleaned up by callind drm_sched_entity_fini(). See also
* drm_sched_entity_destroy().
*
* Returns 0 on success or a negative error code on failure.
*/
@ -92,6 +98,11 @@ EXPORT_SYMBOL(drm_sched_entity_init);
* @sched_list: the list of new drm scheds which will replace
* existing entity->sched_list
* @num_sched_list: number of drm sched in sched_list
*
* Note that this must be called under the same common lock for @entity as
* drm_sched_job_arm() and drm_sched_entity_push_job(), or the driver needs to
* guarantee through some other means that this is never called while new jobs
* can be pushed to @entity.
*/
void drm_sched_entity_modify_sched(struct drm_sched_entity *entity,
struct drm_gpu_scheduler **sched_list,
@ -104,13 +115,6 @@ void drm_sched_entity_modify_sched(struct drm_sched_entity *entity,
}
EXPORT_SYMBOL(drm_sched_entity_modify_sched);
/**
* drm_sched_entity_is_idle - Check if entity is idle
*
* @entity: scheduler entity
*
* Returns true if the entity does not have any unscheduled jobs.
*/
static bool drm_sched_entity_is_idle(struct drm_sched_entity *entity)
{
rmb(); /* for list_empty to work without lock */
@ -123,13 +127,7 @@ static bool drm_sched_entity_is_idle(struct drm_sched_entity *entity)
return false;
}
/**
* drm_sched_entity_is_ready - Check if entity is ready
*
* @entity: scheduler entity
*
* Return true if entity could provide a job.
*/
/* Return true if entity could provide a job. */
bool drm_sched_entity_is_ready(struct drm_sched_entity *entity)
{
if (spsc_queue_peek(&entity->job_queue) == NULL)
@ -192,14 +190,7 @@ long drm_sched_entity_flush(struct drm_sched_entity *entity, long timeout)
}
EXPORT_SYMBOL(drm_sched_entity_flush);
/**
* drm_sched_entity_kill_jobs_cb - helper for drm_sched_entity_kill_jobs
*
* @f: signaled fence
* @cb: our callback structure
*
* Signal the scheduler finished fence when the entity in question is killed.
*/
/* Signal the scheduler finished fence when the entity in question is killed. */
static void drm_sched_entity_kill_jobs_cb(struct dma_fence *f,
struct dma_fence_cb *cb)
{
@ -224,14 +215,6 @@ drm_sched_job_dependency(struct drm_sched_job *job,
return NULL;
}
/**
* drm_sched_entity_kill_jobs - Make sure all remaining jobs are killed
*
* @entity: entity which is cleaned up
*
* Makes sure that all remaining jobs in an entity are killed before it is
* destroyed.
*/
static void drm_sched_entity_kill_jobs(struct drm_sched_entity *entity)
{
struct drm_sched_job *job;
@ -273,9 +256,11 @@ static void drm_sched_entity_kill_jobs(struct drm_sched_entity *entity)
*
* @entity: scheduler entity
*
* This should be called after @drm_sched_entity_do_release. It goes over the
* entity and signals all jobs with an error code if the process was killed.
* Cleanups up @entity which has been initialized by drm_sched_entity_init().
*
* If there are potentially job still in flight or getting newly queued
* drm_sched_entity_flush() must be called first. This function then goes over
* the entity and signals all jobs with an error code if the process was killed.
*/
void drm_sched_entity_fini(struct drm_sched_entity *entity)
{
@ -315,10 +300,10 @@ EXPORT_SYMBOL(drm_sched_entity_fini);
/**
* drm_sched_entity_destroy - Destroy a context entity
*
* @entity: scheduler entity
*
* Calls drm_sched_entity_do_release() and drm_sched_entity_cleanup()
* Calls drm_sched_entity_flush() and drm_sched_entity_fini() as a
* convenience wrapper.
*/
void drm_sched_entity_destroy(struct drm_sched_entity *entity)
{
@ -327,9 +312,7 @@ void drm_sched_entity_destroy(struct drm_sched_entity *entity)
}
EXPORT_SYMBOL(drm_sched_entity_destroy);
/*
* drm_sched_entity_clear_dep - callback to clear the entities dependency
*/
/* drm_sched_entity_clear_dep - callback to clear the entities dependency */
static void drm_sched_entity_clear_dep(struct dma_fence *f,
struct dma_fence_cb *cb)
{
@ -371,11 +354,7 @@ void drm_sched_entity_set_priority(struct drm_sched_entity *entity,
}
EXPORT_SYMBOL(drm_sched_entity_set_priority);
/**
* drm_sched_entity_add_dependency_cb - add callback for the entities dependency
*
* @entity: entity with dependency
*
/*
* Add a callback to the current dependency of the entity to wake up the
* scheduler when the entity becomes available.
*/
@ -423,13 +402,6 @@ static bool drm_sched_entity_add_dependency_cb(struct drm_sched_entity *entity)
return false;
}
/**
* drm_sched_entity_pop_job - get a ready to be scheduled job from the entity
*
* @entity: entity to get the job from
*
* Process all dependencies and try to get one job from the entities queue.
*/
struct drm_sched_job *drm_sched_entity_pop_job(struct drm_sched_entity *entity)
{
struct drm_sched_job *sched_job;
@ -465,14 +437,6 @@ struct drm_sched_job *drm_sched_entity_pop_job(struct drm_sched_entity *entity)
return sched_job;
}
/**
* drm_sched_entity_select_rq - select a new rq for the entity
*
* @entity: scheduler entity
*
* Check all prerequisites and select a new rq for the entity for load
* balancing.
*/
void drm_sched_entity_select_rq(struct drm_sched_entity *entity)
{
struct dma_fence *fence;
@ -520,7 +484,8 @@ void drm_sched_entity_select_rq(struct drm_sched_entity *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_arm()
* under common lock.
* under common lock for the struct drm_sched_entity that was set up for
* @sched_job in drm_sched_job_init().
*
* Returns 0 for success, negative error code otherwise.
*/

145
include/drm/gpu_scheduler.h
View File

@ -53,56 +53,147 @@ enum drm_sched_priority {
* struct drm_sched_entity - A wrapper around a job queue (typically
* attached to the DRM file_priv).
*
* @list: used to append this struct to the list of entities in the
* runqueue.
* @rq: runqueue on which this entity is currently scheduled.
* @sched_list: A list of schedulers (drm_gpu_schedulers).
* Jobs from this entity can be scheduled on any scheduler
* on this list.
* @num_sched_list: number of drm_gpu_schedulers in the sched_list.
* @priority: priority of the entity
* @rq_lock: lock to modify the runqueue to which this entity belongs.
* @job_queue: the list of jobs of this entity.
* @fence_seq: a linearly increasing seqno incremented with each
* new &drm_sched_fence which is part of the entity.
* @fence_context: a unique context for all the fences which belong
* to this entity.
* The &drm_sched_fence.scheduled uses the
* fence_context but &drm_sched_fence.finished uses
* fence_context + 1.
* @dependency: the dependency fence of the job which is on the top
* of the job queue.
* @cb: callback for the dependency fence above.
* @guilty: points to ctx's guilty.
* @fini_status: contains the exit status in case the process was signalled.
* @last_scheduled: points to the finished fence of the last scheduled job.
* @last_user: last group leader pushing a job into the entity.
* @stopped: Marks the enity as removed from rq and destined for termination.
* @entity_idle: Signals when enityt is not in use
*
* Entities will emit jobs in order to their corresponding hardware
* ring, and the scheduler will alternate between entities based on
* scheduling policy.
*/
struct drm_sched_entity {
/**
* @list:
*
* Used to append this struct to the list of entities in the runqueue
* @rq under &drm_sched_rq.entities.
*
* Protected by &drm_sched_rq.lock of @rq.
*/
struct list_head list;
/**
* @rq:
*
* Runqueue on which this entity is currently scheduled.
*
* FIXME: Locking is very unclear for this. Writers are protected by
* @rq_lock, but readers are generally lockless and seem to just race
* with not even a READ_ONCE.
*/
struct drm_sched_rq *rq;
/**
* @sched_list:
*
* A list of schedulers (struct drm_gpu_scheduler). Jobs from this entity can
* be scheduled on any scheduler on this list.
*
* This can be modified by calling drm_sched_entity_modify_sched().
* Locking is entirely up to the driver, see the above function for more
* details.
*
* This will be set to NULL if &num_sched_list equals 1 and @rq has been
* set already.
*
* FIXME: This means priority changes through
* drm_sched_entity_set_priority() will be lost henceforth in this case.
*/
struct drm_gpu_scheduler **sched_list;
/**
* @num_sched_list:
*
* Number of drm_gpu_schedulers in the @sched_list.
*/
unsigned int num_sched_list;
/**
* @priority:
*
* Priority of the entity. This can be modified by calling
* drm_sched_entity_set_priority(). Protected by &rq_lock.
*/
enum drm_sched_priority priority;
/**
* @rq_lock:
*
* Lock to modify the runqueue to which this entity belongs.
*/
spinlock_t rq_lock;
/**
* @job_queue: the list of jobs of this entity.
*/
struct spsc_queue job_queue;
/**
* @fence_seq:
*
* A linearly increasing seqno incremented with each new
* &drm_sched_fence which is part of the entity.
*
* FIXME: Callers of drm_sched_job_arm() need to ensure correct locking,
* this doesn't need to be atomic.
*/
atomic_t fence_seq;
/**
* @fence_context:
*
* A unique context for all the fences which belong to this entity. The
* &drm_sched_fence.scheduled uses the fence_context but
* &drm_sched_fence.finished uses fence_context + 1.
*/
uint64_t fence_context;
/**
* @dependency:
*
* The dependency fence of the job which is on the top of the job queue.
*/
struct dma_fence *dependency;
/**
* @cb:
*
* Callback for the dependency fence above.
*/
struct dma_fence_cb cb;
/**
* @guilty:
*
* Points to entities' guilty.
*/
atomic_t *guilty;
/**
* @last_scheduled:
*
* Points to the finished fence of the last scheduled job. Only written
* by the scheduler thread, can be accessed locklessly from
* drm_sched_job_arm() iff the queue is empty.
*/
struct dma_fence *last_scheduled;
/**
* @last_user: last group leader pushing a job into the entity.
*/
struct task_struct *last_user;
/**
* @stopped:
*
* Marks the enity as removed from rq and destined for
* termination. This is set by calling drm_sched_entity_flush() and by
* drm_sched_fini().
*/
bool stopped;
/**
* @entity_idle:
*
* Signals when entity is not in use, used to sequence entity cleanup in
* drm_sched_entity_fini().
*/
struct completion entity_idle;
};