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* Copyright 2015 Advanced Micro Devices, Inc.
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
#include <drm/spsc_queue.h>
#include <linux/dma-fence.h>
#include <linux/completion.h>
#include <linux/xarray.h>
#include <linux/workqueue.h>
#define MAX_WAIT_SCHED_ENTITY_Q_EMPTY msecs_to_jiffies(1000)
struct drm_gem_object;
struct drm_gpu_scheduler;
struct drm_sched_rq;
/* These are often used as an (initial) index
* to an array, and as such should start at 0.
enum drm_sched_priority {
* struct drm_sched_entity - A wrapper around a job queue (typically
* attached to the DRM file_priv).
* 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;
* struct drm_sched_rq - queue of entities to be scheduled.
* @lock: to modify the entities list.
* @sched: the scheduler to which this rq belongs to.
* @entities: list of the entities to be scheduled.
* @current_entity: the entity which is to be scheduled.
* Run queue is a set of entities scheduling command submissions for
* one specific ring. It implements the scheduling policy that selects
* the next entity to emit commands from.
struct drm_sched_rq {
spinlock_t lock;
struct drm_gpu_scheduler *sched;
struct list_head entities;
struct drm_sched_entity *current_entity;
* struct drm_sched_fence - fences corresponding to the scheduling of a job.
struct drm_sched_fence {
* @scheduled: this fence is what will be signaled by the scheduler
* when the job is scheduled.
struct dma_fence scheduled;
* @finished: this fence is what will be signaled by the scheduler
* when the job is completed.
* When setting up an out fence for the job, you should use
* this, since it's available immediately upon
* drm_sched_job_init(), and the fence returned by the driver
* from run_job() won't be created until the dependencies have
* resolved.
struct dma_fence finished;
* @parent: the fence returned by &drm_sched_backend_ops.run_job
* when scheduling the job on hardware. We signal the
* &drm_sched_fence.finished fence once parent is signalled.
struct dma_fence *parent;
* @sched: the scheduler instance to which the job having this struct
* belongs to.
struct drm_gpu_scheduler *sched;
* @lock: the lock used by the scheduled and the finished fences.
spinlock_t lock;
* @owner: job owner for debugging
void *owner;
struct drm_sched_fence *to_drm_sched_fence(struct dma_fence *f);
* struct drm_sched_job - A job to be run by an entity.
* @queue_node: used to append this struct to the queue of jobs in an entity.
* @list: a job participates in a "pending" and "done" lists.
* @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.
* @work: Helper to reschdeule job kill to different context.
* @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
* limit of the scheduler then the job is marked guilty and will not
* be scheduled further.
* @s_priority: the priority of the job.
* @entity: the entity to which this job belongs.
* @cb: the callback for the parent fence in s_fence.
* A job is created by the driver using drm_sched_job_init(), and
* should call drm_sched_entity_push_job() once it wants the scheduler
* to schedule the job.
struct drm_sched_job {
struct spsc_node queue_node;
struct list_head list;
struct drm_gpu_scheduler *sched;
struct drm_sched_fence *s_fence;
* work is used only after finish_cb has been used and will not be
* accessed anymore.
union {
struct dma_fence_cb finish_cb;
struct work_struct work;
uint64_t id;
atomic_t karma;
enum drm_sched_priority s_priority;
struct drm_sched_entity *entity;
struct dma_fence_cb cb;
* @dependencies:
* Contains the dependencies as struct dma_fence for this job, see
* drm_sched_job_add_dependency() and
* drm_sched_job_add_implicit_dependencies().
struct xarray dependencies;
/** @last_dependency: tracks @dependencies as they signal */
unsigned long last_dependency;
static inline bool drm_sched_invalidate_job(struct drm_sched_job *s_job,
int threshold)
return s_job && atomic_inc_return(&s_job->karma) > threshold;
enum drm_gpu_sched_stat {
DRM_GPU_SCHED_STAT_NONE, /* Reserve 0 */
* struct drm_sched_backend_ops
* Define the backend operations called by the scheduler,
* these functions should be implemented in driver side.
struct drm_sched_backend_ops {
* @dependency:
* Called when the scheduler is considering scheduling this job next, to
* get another struct dma_fence for this job to block on. Once it
* returns NULL, run_job() may be called.
* If a driver exclusively uses drm_sched_job_add_dependency() and
* drm_sched_job_add_implicit_dependencies() this can be ommitted and
* left as NULL.
struct dma_fence *(*dependency)(struct drm_sched_job *sched_job,
struct drm_sched_entity *s_entity);
* @run_job: Called to execute the job once all of the dependencies
* have been resolved. This may be called multiple times, if
* timedout_job() has happened and drm_sched_job_recovery()
* decides to try it again.
struct dma_fence *(*run_job)(struct drm_sched_job *sched_job);
* @timedout_job: Called when a job has taken too long to execute,
* to trigger GPU recovery.
* This method is called in a workqueue context.
* Drivers typically issue a reset to recover from GPU hangs, and this
* procedure usually follows the following workflow:
* 1. Stop the scheduler using drm_sched_stop(). This will park the
* scheduler thread and cancel the timeout work, guaranteeing that
* nothing is queued while we reset the hardware queue
* 2. Try to gracefully stop non-faulty jobs (optional)
* 3. Issue a GPU reset (driver-specific)
* 4. Re-submit jobs using drm_sched_resubmit_jobs()
* 5. Restart the scheduler using drm_sched_start(). At that point, new
* jobs can be queued, and the scheduler thread is unblocked
* Note that some GPUs have distinct hardware queues but need to reset
* the GPU globally, which requires extra synchronization between the
* timeout handler of the different &drm_gpu_scheduler. One way to
* achieve this synchronization is to create an ordered workqueue
* (using alloc_ordered_workqueue()) at the driver level, and pass this
* queue to drm_sched_init(), to guarantee that timeout handlers are
* executed sequentially. The above workflow needs to be slightly
* adjusted in that case:
* 1. Stop all schedulers impacted by the reset using drm_sched_stop()
* 2. Try to gracefully stop non-faulty jobs on all queues impacted by
* the reset (optional)
* 3. Issue a GPU reset on all faulty queues (driver-specific)
* 4. Re-submit jobs on all schedulers impacted by the reset using
* drm_sched_resubmit_jobs()
* 5. Restart all schedulers that were stopped in step #1 using
* drm_sched_start()
* Return DRM_GPU_SCHED_STAT_NOMINAL, when all is normal,
* and the underlying driver has started or completed recovery.
* Return DRM_GPU_SCHED_STAT_ENODEV, if the device is no longer
* available, i.e. has been unplugged.
enum drm_gpu_sched_stat (*timedout_job)(struct drm_sched_job *sched_job);
* @free_job: Called once the job's finished fence has been signaled
* and it's time to clean it up.
void (*free_job)(struct drm_sched_job *sched_job);
* struct drm_gpu_scheduler
* @ops: backend operations provided by the driver.
* @hw_submission_limit: the max size of the hardware queue.
* @timeout: the time after which a job is removed from the scheduler.
* @name: name of the ring for which this scheduler is being used.
* @sched_rq: priority wise array of run queues.
* @wake_up_worker: the wait queue on which the scheduler sleeps until a job
* is ready to be scheduled.
* @job_scheduled: once @drm_sched_entity_do_release is called the scheduler
* waits on this wait queue until all the scheduled jobs are
* finished.
* @hw_rq_count: the number of jobs currently in the hardware queue.
* @job_id_count: used to assign unique id to the each job.
* @timeout_wq: workqueue used to queue @work_tdr
* @work_tdr: schedules a delayed call to @drm_sched_job_timedout after the
* timeout interval is over.
* @thread: the kthread on which the scheduler which run.
* @pending_list: the list of jobs which are currently in the job queue.
* @job_list_lock: lock to protect the pending_list.
* @hang_limit: once the hangs by a job crosses this limit then it is marked
* guilty and it will no longer be considered for scheduling.
* @score: score to help loadbalancer pick a idle sched
* @_score: score used when the driver doesn't provide one
* @ready: marks if the underlying HW is ready to work
* @free_guilty: A hit to time out handler to free the guilty job.
* One scheduler is implemented for each hardware ring.
struct drm_gpu_scheduler {
const struct drm_sched_backend_ops *ops;
uint32_t hw_submission_limit;
long timeout;
const char *name;
struct drm_sched_rq sched_rq[DRM_SCHED_PRIORITY_COUNT];
wait_queue_head_t wake_up_worker;
wait_queue_head_t job_scheduled;
atomic_t hw_rq_count;
atomic64_t job_id_count;
struct workqueue_struct *timeout_wq;
struct delayed_work work_tdr;
struct task_struct *thread;
struct list_head pending_list;
spinlock_t job_list_lock;
int hang_limit;
atomic_t *score;
atomic_t _score;
bool ready;
bool free_guilty;
struct device *dev;
int drm_sched_init(struct drm_gpu_scheduler *sched,
const struct drm_sched_backend_ops *ops,
uint32_t hw_submission, unsigned hang_limit,
long timeout, struct workqueue_struct *timeout_wq,
atomic_t *score, const char *name, struct device *dev);
void drm_sched_fini(struct drm_gpu_scheduler *sched);
int drm_sched_job_init(struct drm_sched_job *job,
struct drm_sched_entity *entity,
void *owner);
void drm_sched_job_arm(struct drm_sched_job *job);
int drm_sched_job_add_dependency(struct drm_sched_job *job,
struct dma_fence *fence);
int drm_sched_job_add_implicit_dependencies(struct drm_sched_job *job,
struct drm_gem_object *obj,
bool write);
void drm_sched_entity_modify_sched(struct drm_sched_entity *entity,
struct drm_gpu_scheduler **sched_list,
unsigned int num_sched_list);
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, 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_resubmit_jobs_ext(struct drm_gpu_scheduler *sched, int max);
void drm_sched_increase_karma(struct drm_sched_job *bad);
void drm_sched_reset_karma(struct drm_sched_job *bad);
void drm_sched_increase_karma_ext(struct drm_sched_job *bad, int type);
bool drm_sched_dependency_optimized(struct dma_fence* fence,
struct drm_sched_entity *entity);
void drm_sched_fault(struct drm_gpu_scheduler *sched);
void drm_sched_job_kickout(struct drm_sched_job *s_job);
void drm_sched_rq_add_entity(struct drm_sched_rq *rq,
struct drm_sched_entity *entity);
void drm_sched_rq_remove_entity(struct drm_sched_rq *rq,
struct drm_sched_entity *entity);
int drm_sched_entity_init(struct drm_sched_entity *entity,
enum drm_sched_priority priority,
struct drm_gpu_scheduler **sched_list,
unsigned int num_sched_list,
atomic_t *guilty);
long drm_sched_entity_flush(struct drm_sched_entity *entity, long timeout);
void drm_sched_entity_fini(struct drm_sched_entity *entity);
void drm_sched_entity_destroy(struct drm_sched_entity *entity);
void drm_sched_entity_select_rq(struct drm_sched_entity *entity);
struct drm_sched_job *drm_sched_entity_pop_job(struct drm_sched_entity *entity);
void drm_sched_entity_push_job(struct drm_sched_job *sched_job);
void drm_sched_entity_set_priority(struct drm_sched_entity *entity,
enum drm_sched_priority priority);
bool drm_sched_entity_is_ready(struct drm_sched_entity *entity);
struct drm_sched_fence *drm_sched_fence_alloc(
struct drm_sched_entity *s_entity, void *owner);
void drm_sched_fence_init(struct drm_sched_fence *fence,
struct drm_sched_entity *entity);
void drm_sched_fence_free(struct drm_sched_fence *fence);
void drm_sched_fence_scheduled(struct drm_sched_fence *fence);
void drm_sched_fence_finished(struct drm_sched_fence *fence);
unsigned long drm_sched_suspend_timeout(struct drm_gpu_scheduler *sched);
void drm_sched_resume_timeout(struct drm_gpu_scheduler *sched,
unsigned long remaining);
struct drm_gpu_scheduler *
drm_sched_pick_best(struct drm_gpu_scheduler **sched_list,
unsigned int num_sched_list);