drm/etnaviv: protect sched job submission with fence mutex

The documentation of drm_sched_job_init and drm_sched_entity_push_job has
been clarified. Both functions should be called under a shared lock, to
avoid jobs getting pushed into the scheduler queue in a different order
than their sched_fence seqnos, which will confuse checks that are looking
at the seqnos to infer information about completion order.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>

4 files changed, 21 insertions, 11 deletions

diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c b/drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c
index 46ecd3e66ac9..983e67f19e45 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c
@@ -388,9 +388,9 @@ static void submit_cleanup(struct kref *kref)
                 dma_fence_put(submit->in_fence);
         if (submit->out_fence) {
                 /* first remove from IDR, so fence can not be found anymore */
-                mutex_lock(&submit->gpu->fence_idr_lock);
+                mutex_lock(&submit->gpu->fence_lock);
                 idr_remove(&submit->gpu->fence_idr, submit->out_fence_id);
-                mutex_unlock(&submit->gpu->fence_idr_lock);
+                mutex_unlock(&submit->gpu->fence_lock);
                 dma_fence_put(submit->out_fence);
         }
         kfree(submit->pmrs);
diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gpu.c b/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
index 686f6552db48..18c2224ba0b8 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_gpu.c
@@ -1733,7 +1733,7 @@ static int etnaviv_gpu_platform_probe(struct platform_device *pdev)
 
         gpu->dev = &pdev->dev;
         mutex_init(&gpu->lock);
-        mutex_init(&gpu->fence_idr_lock);
+        mutex_init(&gpu->fence_lock);
 
         /* Map registers: */
         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gpu.h b/drivers/gpu/drm/etnaviv/etnaviv_gpu.h
index 90f17ff7888e..9a75a6937268 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_gpu.h
+++ b/drivers/gpu/drm/etnaviv/etnaviv_gpu.h
@@ -118,7 +118,7 @@ struct etnaviv_gpu {
         u32 idle_mask;
 
         /* Fencing support */
-        struct mutex fence_idr_lock;
+        struct mutex fence_lock;
         struct idr fence_idr;
         u32 next_fence;
         u32 active_fence;
diff --git a/drivers/gpu/drm/etnaviv/etnaviv_sched.c b/drivers/gpu/drm/etnaviv/etnaviv_sched.c
index 50d6b88cb7aa..b267d9c4d91c 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_sched.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_sched.c
@@ -140,28 +140,38 @@ static const struct drm_sched_backend_ops etnaviv_sched_ops = {
 int etnaviv_sched_push_job(struct drm_sched_entity *sched_entity,
                            struct etnaviv_gem_submit *submit)
 {
-        int ret;
+        int ret = 0;
+
+        /*
+         * Hold the fence lock across the whole operation to avoid jobs being
+         * pushed out of order with regard to their sched fence seqnos as
+         * allocated in drm_sched_job_init.
+         */
+        mutex_lock(&submit->gpu->fence_lock);
 
         ret = drm_sched_job_init(&submit->sched_job, &submit->gpu->sched,
                                  sched_entity, submit->cmdbuf.ctx);
         if (ret)
-                return ret;
+                goto out_unlock;
 
         submit->out_fence = dma_fence_get(&submit->sched_job.s_fence->finished);
-        mutex_lock(&submit->gpu->fence_idr_lock);
         submit->out_fence_id = idr_alloc_cyclic(&submit->gpu->fence_idr,
                                                 submit->out_fence, 0,
                                                 INT_MAX, GFP_KERNEL);
-        mutex_unlock(&submit->gpu->fence_idr_lock);
-        if (submit->out_fence_id < 0)
-                return -ENOMEM;
+        if (submit->out_fence_id < 0) {
+                ret = -ENOMEM;
+                goto out_unlock;
+        }
 
         /* the scheduler holds on to the job now */
         kref_get(&submit->refcount);
 
         drm_sched_entity_push_job(&submit->sched_job, sched_entity);
 
-        return 0;
+out_unlock:
+        mutex_unlock(&submit->gpu->fence_lock);
+
+        return ret;
 }
 
 int etnaviv_sched_init(struct etnaviv_gpu *gpu)