drm/nouveau: Add new callback for scheduler teardown

There is a new callback for always tearing the scheduler down in a
leak-free, deadlock-free manner.

Port Nouveau as its first user by providing the scheduler with a
callback that ensures the fence context gets killed in drm_sched_fini().

Acked-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Philipp Stanner <phasta@kernel.org>
Link: https://lore.kernel.org/r/20250710125412.128476-9-phasta@kernel.org

Author: Philipp Stanner

drivers/gpu/drm/nouveau/nouveau_fence.c

@@ -240,6 +240,21 @@ nouveau_fence_emit(struct nouveau_fence *fence)
 	return ret;
 }
 
+void
+nouveau_fence_cancel(struct nouveau_fence *fence)
+{
+	struct nouveau_fence_chan *fctx = nouveau_fctx(fence);
+	unsigned long flags;
+
+	spin_lock_irqsave(&fctx->lock, flags);
+	if (!dma_fence_is_signaled_locked(&fence->base)) {
+		dma_fence_set_error(&fence->base, -ECANCELED);
+		if (nouveau_fence_signal(fence))
+			nvif_event_block(&fctx->event);
+	}
+	spin_unlock_irqrestore(&fctx->lock, flags);
+}
+
 bool
 nouveau_fence_done(struct nouveau_fence *fence)
 {

drivers/gpu/drm/nouveau/nouveau_fence.h

@@ -29,6 +29,7 @@ void nouveau_fence_unref(struct nouveau_fence **);
 
 int  nouveau_fence_emit(struct nouveau_fence *);
 bool nouveau_fence_done(struct nouveau_fence *);
+void nouveau_fence_cancel(struct nouveau_fence *fence);
 int  nouveau_fence_wait(struct nouveau_fence *, bool lazy, bool intr);
 int  nouveau_fence_sync(struct nouveau_bo *, struct nouveau_channel *, bool exclusive, bool intr);
 

drivers/gpu/drm/nouveau/nouveau_sched.c

@@ -11,6 +11,7 @@
 #include "nouveau_exec.h"
 #include "nouveau_abi16.h"
 #include "nouveau_sched.h"
+#include "nouveau_chan.h"
 
 #define NOUVEAU_SCHED_JOB_TIMEOUT_MS		10000
 
@@ -393,10 +394,23 @@ nouveau_sched_free_job(struct drm_sched_job *sched_job)
 	nouveau_job_fini(job);
 }
 
+static void
+nouveau_sched_cancel_job(struct drm_sched_job *sched_job)
+{
+	struct nouveau_fence *fence;
+	struct nouveau_job *job;
+
+	job = to_nouveau_job(sched_job);
+	fence = to_nouveau_fence(job->done_fence);
+
+	nouveau_fence_cancel(fence);
+}
+
 static const struct drm_sched_backend_ops nouveau_sched_ops = {
 	.run_job = nouveau_sched_run_job,
 	.timedout_job = nouveau_sched_timedout_job,
 	.free_job = nouveau_sched_free_job,
+	.cancel_job = nouveau_sched_cancel_job,
 };
 
 static int
@@ -482,7 +496,6 @@ nouveau_sched_create(struct nouveau_sched **psched, struct nouveau_drm *drm,
 	return 0;
 }
 
-
 static void
 nouveau_sched_fini(struct nouveau_sched *sched)
 {