linux-kernel - [PATCH v2 2/2] drm/sched: warn about drm_sched_job

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Message-ID: <20240828094133.17402-4-pstanner@redhat.com>
Date: Wed, 28 Aug 2024 11:41:35 +0200
From: Philipp Stanner <pstanner@...hat.com>
To: Luben Tuikov <ltuikov89@...il.com>,
	Matthew Brost <matthew.brost@...el.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>,
	Daniel Vetter <daniel@...ll.ch>,
	Danilo Krummrich <dakr@...hat.com>
Cc: dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	Philipp Stanner <pstanner@...hat.com>
Subject: [PATCH v2 2/2] drm/sched: warn about drm_sched_job_init()'s partial init

drm_sched_job_init()'s name suggests that after the function succeeded,
parameter "job" will be fully initialized. This is not the case; some
members are only later set, notably "job->sched" by drm_sched_job_arm().

Document that drm_sched_job_init() does not set all struct members.

Document that job->sched in particular is uninitialized before
drm_sched_job_arm().

Signed-off-by: Philipp Stanner <pstanner@...hat.com>
---
Changes in v2:
  - Change grammar in the new comments a bit.
---
 drivers/gpu/drm/scheduler/sched_main.c | 4 ++++
 include/drm/gpu_scheduler.h            | 7 +++++++
 2 files changed, 11 insertions(+)

diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index b0c8ad10b419..721373938c1e 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -781,6 +781,10 @@ EXPORT_SYMBOL(drm_sched_resubmit_jobs);
  * 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.
  *
+ * Note that this function does not assign a valid value to each struct member
+ * of struct drm_sched_job. Take a look at that struct's documentation to see
+ * who sets which struct member with what lifetime.
+ *
  * 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
diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
index 5acc64954a88..04a268cd22f1 100644
--- a/include/drm/gpu_scheduler.h
+++ b/include/drm/gpu_scheduler.h
@@ -337,6 +337,13 @@ struct drm_sched_fence *to_drm_sched_fence(struct dma_fence *f);
 struct drm_sched_job {
 	struct spsc_node		queue_node;
 	struct list_head		list;
+
+	/*
+	 * The scheduler this job is or will be scheduled on.
+	 *
+	 * Gets set by drm_sched_arm(). Valid until the scheduler's backend_ops
+	 * callback "free_job()" has been called.
+	 */
 	struct drm_gpu_scheduler	*sched;
 	struct drm_sched_fence		*s_fence;
 
-- 
2.46.0