On 21/03/2025 15:58, Christian König wrote:
Sometimes drivers need to be able to submit multiple jobs which depend on
each other to different schedulers at the same time, but using
drm_sched_job_add_dependency() can't fail any more after the first job is
initialized.
This function preallocate memory for dependency slots so that no ENOMEM
can come later while adding dependencies.
v2: rework implementation an documentation
Signed-off-by: Christian König <christian.koe...@amd.com>
---
drivers/gpu/drm/scheduler/sched_main.c | 44 ++++++++++++++++++++++++--
include/drm/gpu_scheduler.h | 2 ++
2 files changed, 43 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/scheduler/sched_main.c
b/drivers/gpu/drm/scheduler/sched_main.c
index 4d4219fbe49d..ee3701f346b2 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -852,6 +852,39 @@ void drm_sched_job_arm(struct drm_sched_job *job)
}
EXPORT_SYMBOL(drm_sched_job_arm);
+/**
+ * drm_sched_job_prealloc_dependency_slots - avoid ENOMEM on adding
dependencies
+ * @job: scheduler job where dependencies will be added
+ * @num_deps: number of dependencies to preallocate slots for
+ *
+ * Sometimes drivers need to be able to submit multiple jobs which depend on
+ * each other to different schedulers at the same time, but using
+ * drm_sched_job_add_dependency() can't fail any more after the first job is
+ * initialized.
+ *
+ * This function preallocate memory for dependency slots so that no ENOMEM can
+ * come later while adding dependencies.
+ *
+ * Return:
+ * 0 on success, or an error on failing to expand the array.
+ */
+int drm_sched_job_prealloc_dependency_slots(struct drm_sched_job *job,
+ unsigned int num_deps)
+{
+ u32 id = 0;
+ int ret;
+
+ while (num_deps--) {
+ ret = xa_alloc(&job->dependencies, &id, XA_ZERO_ENTRY,
+ xa_limit_32b, GFP_KERNEL);
+ if (ret != 0)
+ return ret;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL(drm_sched_job_prealloc_dependency_slots);
+
/**
* drm_sched_job_add_dependency - adds the fence as a job dependency
* @job: scheduler job to add the dependencies to
@@ -878,10 +911,15 @@ int drm_sched_job_add_dependency(struct drm_sched_job
*job,
* engines involved, rather than the number of BOs.
*/
xa_for_each(&job->dependencies, index, entry) {
- if (entry->context != fence->context)
+ if (xa_is_zero(entry)) {
If xa_for_each shows them I think we also need to skip them in
drm_sched_job_dependency() and drm_sched_job_cleanup(). Or remove the
unused ones at arm time. Hm, we could also put a noisy fail if
add_dependency allocates after a job is armed. (I can imagine a few unit
tests for this once we merge them.)
Regards,
Tvrtko
+ /*
+ * Reserved entries must not alloc memory, but let's
+ * use GFP_ATOMIC just to be on the defensive side.
+ */
+ xa_store(&job->dependencies, index, fence, GFP_ATOMIC);
+ } else if (entry->context != fence->context) {
continue;
-
- if (dma_fence_is_later(fence, entry)) {
+ } else if (dma_fence_is_later(fence, entry)) {
dma_fence_put(entry);
xa_store(&job->dependencies, index, fence, GFP_KERNEL);
} else {
diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
index 1a7e377d4cbb..916e820b27ff 100644
--- a/include/drm/gpu_scheduler.h
+++ b/include/drm/gpu_scheduler.h
@@ -632,6 +632,8 @@ int drm_sched_job_init(struct drm_sched_job *job,
u32 credits, void *owner);
void drm_sched_job_arm(struct drm_sched_job *job);
void drm_sched_entity_push_job(struct drm_sched_job *sched_job);
+int drm_sched_job_prealloc_dependency_slots(struct drm_sched_job *job,
+ unsigned int num_deps);
int drm_sched_job_add_dependency(struct drm_sched_job *job,
struct dma_fence *fence);
int drm_sched_job_add_syncobj_dependency(struct drm_sched_job *job,
