drm/sched: Split drm_sched_job_init

This is a very confusingly named function, because not just does it
init an object, it arms it and provides a point of no return for
pushing a job into the scheduler. It would be nice if that's a bit
clearer in the interface.

But the real reason is that I want to push the dependency tracking
helpers into the scheduler code, and that means drm_sched_job_init
must be called a lot earlier, without arming the job.

v2:
- don't change .gitignore (Steven)
- don't forget v3d (Emma)

v3: Emma noticed that I leak the memory allocated in
drm_sched_job_init if we bail out before the point of no return in
subsequent driver patches. To be able to fix this change
drm_sched_job_cleanup() so it can handle being called both before and
after drm_sched_job_arm().

Also improve the kerneldoc for this.

v4:
- Fix the drm_sched_job_cleanup logic, I inverted the booleans, as
  usual (Melissa)

- Christian pointed out that drm_sched_entity_select_rq() also needs
  to be moved into drm_sched_job_arm, which made me realize that the
  job->id definitely needs to be moved too.

  Shuffle things to fit between job_init and job_arm.

v5:
Reshuffle the split between init/arm once more, amdgpu abuses
drm_sched.ready to signal gpu reset failures. Also document this
somewhat. (Christian)

v6:
Rebase on top of the msm drm/sched support. Note that the
drm_sched_job_init() call is completely misplaced, and hence also the
split-out drm_sched_entity_push_job(). I've put in a FIXME which the next
patch will address.

v7: Drop the FIXME in msm, after discussions with Rob I agree it shouldn't
be a problem where it is now.

Acked-by: Christian König <christian.koenig@amd.com>
Acked-by: Melissa Wen <mwen@igalia.com>
Cc: Melissa Wen <melissa.srw@gmail.com>
Acked-by: Emma Anholt <emma@anholt.net>
Acked-by: Steven Price <steven.price@arm.com> (v2)
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com> (v5)
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Russell King <linux+etnaviv@armlinux.org.uk>
Cc: Christian Gmeiner <christian.gmeiner@gmail.com>
Cc: Qiang Yu <yuq825@gmail.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Cc: Steven Price <steven.price@arm.com>
Cc: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Adam Borowski <kilobyte@angband.pl>
Cc: Nick Terrell <terrelln@fb.com>
Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Cc: Paul Menzel <pmenzel@molgen.mpg.de>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Nirmoy Das <nirmoy.das@amd.com>
Cc: Deepak R Varma <mh12gx2825@gmail.com>
Cc: Lee Jones <lee.jones@linaro.org>
Cc: Kevin Wang <kevin1.wang@amd.com>
Cc: Chen Li <chenli@uniontech.com>
Cc: Luben Tuikov <luben.tuikov@amd.com>
Cc: "Marek Olšák" <marek.olsak@amd.com>
Cc: Dennis Li <Dennis.Li@amd.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Cc: Sonny Jiang <sonny.jiang@amd.com>
Cc: Boris Brezillon <boris.brezillon@collabora.com>
Cc: Tian Tao <tiantao6@hisilicon.com>
Cc: etnaviv@lists.freedesktop.org
Cc: lima@lists.freedesktop.org
Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Cc: Emma Anholt <emma@anholt.net>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Sean Paul <sean@poorly.run>
Cc: linux-arm-msm@vger.kernel.org
Cc: freedreno@lists.freedesktop.org
Link: https://patchwork.freedesktop.org/patch/msgid/20210817084917.3555822-1-daniel.vetter@ffwll.ch

3 files changed, 73 insertions, 21 deletions

diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
index 79554aa4dbb1..f7347c284886 100644
--- a/drivers/gpu/drm/scheduler/sched_entity.c
+++ b/drivers/gpu/drm/scheduler/sched_entity.c
@@ -485,9 +485,9 @@ void drm_sched_entity_select_rq(struct drm_sched_entity *entity)
  * @sched_job: job to submit
  * @entity: scheduler 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_init under common lock.
+ * 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.
  *
  * Returns 0 for success, negative error code otherwise.
  */
diff --git a/drivers/gpu/drm/scheduler/sched_fence.c b/drivers/gpu/drm/scheduler/sched_fence.c
index 69de2c76731f..bcea035cf4c6 100644
--- a/drivers/gpu/drm/scheduler/sched_fence.c
+++ b/drivers/gpu/drm/scheduler/sched_fence.c
@@ -90,7 +90,7 @@ static const char *drm_sched_fence_get_timeline_name(struct dma_fence *f)
  *
  * Free up the fence memory after the RCU grace period.
  */
-static void drm_sched_fence_free(struct rcu_head *rcu)
+void drm_sched_fence_free(struct rcu_head *rcu)
 {
 	struct dma_fence *f = container_of(rcu, struct dma_fence, rcu);
 	struct drm_sched_fence *fence = to_drm_sched_fence(f);
@@ -152,27 +152,32 @@ struct drm_sched_fence *to_drm_sched_fence(struct dma_fence *f)
 }
 EXPORT_SYMBOL(to_drm_sched_fence);
 
-struct drm_sched_fence *drm_sched_fence_create(struct drm_sched_entity *entity,
-					       void *owner)
+struct drm_sched_fence *drm_sched_fence_alloc(struct drm_sched_entity *entity,
+					      void *owner)
 {
 	struct drm_sched_fence *fence = NULL;
-	unsigned seq;
 
 	fence = kmem_cache_zalloc(sched_fence_slab, GFP_KERNEL);
 	if (fence == NULL)
 		return NULL;
 
 	fence->owner = owner;
-	fence->sched = entity->rq->sched;
 	spin_lock_init(&fence->lock);
 
+	return fence;
+}
+
+void drm_sched_fence_init(struct drm_sched_fence *fence,
+			  struct drm_sched_entity *entity)
+{
+	unsigned seq;
+
+	fence->sched = entity->rq->sched;
 	seq = atomic_inc_return(&entity->fence_seq);
 	dma_fence_init(&fence->scheduled, &drm_sched_fence_ops_scheduled,
 		       &fence->lock, entity->fence_context, seq);
 	dma_fence_init(&fence->finished, &drm_sched_fence_ops_finished,
 		       &fence->lock, entity->fence_context + 1, seq);
-
-	return fence;
 }
 
 module_init(drm_sched_fence_slab_init);
diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index 67382621b429..719b1a6dbb90 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -48,9 +48,11 @@
 #include <linux/wait.h>
 #include <linux/sched.h>
 #include <linux/completion.h>
+#include <linux/dma-resv.h>
 #include <uapi/linux/sched/types.h>
 
 #include <drm/drm_print.h>
+#include <drm/drm_gem.h>
 #include <drm/gpu_scheduler.h>
 #include <drm/spsc_queue.h>
 
@@ -564,7 +566,6 @@ EXPORT_SYMBOL(drm_sched_resubmit_jobs_ext);
 
 /**
  * drm_sched_job_init - init a scheduler job
- *
  * @job: scheduler job to init
  * @entity: scheduler entity to use
  * @owner: job owner for debugging
@@ -572,27 +573,28 @@ EXPORT_SYMBOL(drm_sched_resubmit_jobs_ext);
  * Refer to drm_sched_entity_push_job() documentation
  * for locking considerations.
  *
+ * Drivers must make sure drm_sched_job_cleanup() if this function returns
+ * successfully, even when @job is aborted before drm_sched_job_arm() is called.
+ *
+ * WARNING: amdgpu abuses &drm_sched.ready to signal when the hardware
+ * has died, which can mean that there's no valid runqueue for a @entity.
+ * This function returns -ENOENT in this case (which probably should be -EIO as
+ * a more meanigful return value).
+ *
  * Returns 0 for success, negative error code otherwise.
  */
 int drm_sched_job_init(struct drm_sched_job *job,
 		       struct drm_sched_entity *entity,
 		       void *owner)
 {
-	struct drm_gpu_scheduler *sched;
-
 	drm_sched_entity_select_rq(entity);
 	if (!entity->rq)
 		return -ENOENT;
 
-	sched = entity->rq->sched;
-
-	job->sched = sched;
 	job->entity = entity;
-	job->s_priority = entity->rq - sched->sched_rq;
-	job->s_fence = drm_sched_fence_create(entity, owner);
+	job->s_fence = drm_sched_fence_alloc(entity, owner);
 	if (!job->s_fence)
 		return -ENOMEM;
-	job->id = atomic64_inc_return(&sched->job_id_count);
 
 	INIT_LIST_HEAD(&job->list);
 
@@ -601,13 +603,58 @@ int drm_sched_job_init(struct drm_sched_job *job,
 EXPORT_SYMBOL(drm_sched_job_init);
 
 /**
- * drm_sched_job_cleanup - clean up scheduler job resources
+ * drm_sched_job_arm - arm a scheduler job for execution
+ * @job: scheduler job to arm
+ *
+ * This arms a scheduler job for execution. Specifically it initializes the
+ * &drm_sched_job.s_fence of @job, so that it can be attached to struct dma_resv
+ * or other places that need to track the completion of this job.
+ *
+ * Refer to drm_sched_entity_push_job() documentation for locking
+ * considerations.
  *
+ * This can only be called if drm_sched_job_init() succeeded.
+ */
+void drm_sched_job_arm(struct drm_sched_job *job)
+{
+	struct drm_gpu_scheduler *sched;
+	struct drm_sched_entity *entity = job->entity;
+
+	BUG_ON(!entity);
+
+	sched = entity->rq->sched;
+
+	job->sched = sched;
+	job->s_priority = entity->rq - sched->sched_rq;
+	job->id = atomic64_inc_return(&sched->job_id_count);
+
+	drm_sched_fence_init(job->s_fence, job->entity);
+}
+EXPORT_SYMBOL(drm_sched_job_arm);
+
+/**
+ * drm_sched_job_cleanup - clean up scheduler job resources
  * @job: scheduler job to clean up
+ *
+ * Cleans up the resources allocated with drm_sched_job_init().
+ *
+ * Drivers should call this from their error unwind code if @job is aborted
+ * before drm_sched_job_arm() is called.
+ *
+ * After that point of no return @job is committed to be executed by the
+ * scheduler, and this function should be called from the
+ * &drm_sched_backend_ops.free_job callback.
  */
 void drm_sched_job_cleanup(struct drm_sched_job *job)
 {
-	dma_fence_put(&job->s_fence->finished);
+	if (kref_read(&job->s_fence->finished.refcount)) {
+		/* drm_sched_job_arm() has been called */
+		dma_fence_put(&job->s_fence->finished);
+	} else {
+		/* aborted job before committing to run it */
+		drm_sched_fence_free(&job->s_fence->finished.rcu);
+	}
+
 	job->s_fence = NULL;
 }
 EXPORT_SYMBOL(drm_sched_job_cleanup);