[RFC 3/4] drm/sched: Keep module reference while there are active fences

[Tvrtko Ursulin]

Continuing the theme from previous patches. This time round we deal with
the problem that it is possible to unbind the driver from the PCI device
with an active sync file fence.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at igalia.com>
Cc: Christian König <christian.koenig at amd.com>
Cc: Danilo Krummrich <dakr at kernel.org>
Cc: Lucas De Marchi <lucas.demarchi at intel.com>
Cc: Matthew Brost <matthew.brost at intel.com>
Cc: Philipp Stanner <phasta at kernel.org>
Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
---
 drivers/gpu/drm/scheduler/sched_fence.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/scheduler/sched_fence.c b/drivers/gpu/drm/scheduler/sched_fence.c
index e971528504a5..178077f03e44 100644
--- a/drivers/gpu/drm/scheduler/sched_fence.c
+++ b/drivers/gpu/drm/scheduler/sched_fence.c
@@ -115,8 +115,10 @@ static void drm_sched_fence_free_rcu(struct rcu_head *rcu)
 void drm_sched_fence_free(struct drm_sched_fence *fence)
 {
 	/* This function should not be called if the fence has been initialized. */
-	if (!WARN_ON_ONCE(fence->sched))
+	if (!WARN_ON_ONCE(fence->sched)) {
 		kmem_cache_free(sched_fence_slab, fence);
+		module_put(THIS_MODULE);
+	}
 }
 
 /**
@@ -133,6 +135,7 @@ static void drm_sched_fence_release_scheduled(struct dma_fence *f)
 
 	dma_fence_put(fence->parent);
 	call_rcu(&fence->finished.rcu, drm_sched_fence_free_rcu);
+	module_put(THIS_MODULE);
 }
 
 /**
@@ -210,9 +213,14 @@ struct drm_sched_fence *drm_sched_fence_alloc(struct drm_sched_entity *entity,
 {
 	struct drm_sched_fence *fence = NULL;
 
+	if (!try_module_get(THIS_MODULE))
+		return NULL;
+
 	fence = kmem_cache_zalloc(sched_fence_slab, GFP_KERNEL);
-	if (fence == NULL)
+	if (!fence) {
+		module_put(THIS_MODULE);
 		return NULL;
+	}
 
 	fence->owner = owner;
 	spin_lock_init(&fence->lock);
-- 
2.48.0