On 18/03/2025 12:03, Christian König wrote:
The problem is that drivers sometimes need to add dependencies without
allocating any memory.
Add a function which preallocates slots by inserting signaled stub fences
into the dependency array.
Signed-off-by: Christian König <christian.koenig@xxxxxxx>
---
drivers/gpu/drm/scheduler/sched_main.c | 41 ++++++++++++++++++++++++--
include/drm/gpu_scheduler.h | 2 ++
2 files changed, 40 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index 4d4219fbe49d..2085eea89513 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -852,6 +852,38 @@ 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
+ *
+ * Preallocate memory 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)
+{
+ struct dma_fence *fence;
+ u32 id = 0;
+ int ret;
+
+ while (num_deps--) {
+ fence = dma_fence_get_stub();
+ ret = xa_alloc(&job->dependencies, &id, fence, xa_limit_32b,
+ GFP_KERNEL);
+ if (ret != 0) {
+ dma_fence_put(fence);
+ 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 +910,12 @@ 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)
+ bool signaled = dma_fence_is_signaled(entry);
I so dislike dma_fence_is_signaled() due it leaking the fence signaling
annotations to unsuspecting callers. I hope it doesn't mark someone's
lock/mutex as the critical signalling path..
Regards,
Tvrtko
+
+ if (!signaled && entry->context != fence->context)
continue;
- if (dma_fence_is_later(fence, entry)) {
+ if (signaled || dma_fence_is_later(fence, entry)) {
dma_fence_put(entry);
xa_store(&job->dependencies, index, fence, GFP_KERNEL);
} else {
@@ -890,7 +924,8 @@ int drm_sched_job_add_dependency(struct drm_sched_job *job,
return 0;
}
- ret = xa_alloc(&job->dependencies, &id, fence, xa_limit_32b, GFP_KERNEL);
+ ret = xa_alloc(&job->dependencies, &id, fence, xa_limit_32b,
+ GFP_KERNEL);
if (ret != 0)
dma_fence_put(fence);
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,
