drm/panfrost: Make sure the shrinker does not reclaim referenced BOs

commit 7e0cf7e9936c4358b0863357b90aa12afe6489da upstream.

Userspace might tag a BO purgeable while it's still referenced by GPU
jobs. We need to make sure the shrinker does not purge such BOs until
all jobs referencing it are finished.

Fixes: 013b65101315 ("drm/panfrost: Add madvise and shrinker support")
Cc: <stable@vger.kernel.org>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20191129135908.2439529-9-boris.brezillon@collabora.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
index 5906c80..f57dd19 100644 (file)
--- a/drivers/gpu/drm/panfrost/panfrost_drv.c
+++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
@@ -166,6 +166,7 @@ panfrost_lookup_bos(struct drm_device *dev,
                        break;
                }
 
+               atomic_inc(&bo->gpu_usecount);
                job->mappings[i] = mapping;
        }
 

diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.h b/drivers/gpu/drm/panfrost/panfrost_gem.h
index ca1bc90..b3517ff 100644 (file)
--- a/drivers/gpu/drm/panfrost/panfrost_gem.h
+++ b/drivers/gpu/drm/panfrost/panfrost_gem.h
@@ -30,6 +30,12 @@ struct panfrost_gem_object {
                struct mutex lock;
        } mappings;
 
+       /*
+        * Count the number of jobs referencing this BO so we don't let the
+        * shrinker reclaim this object prematurely.
+        */
+       atomic_t gpu_usecount;
+
        bool noexec             :1;
        bool is_heap            :1;
 };

diff --git a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
index f5dd7b2..288e46c 100644 (file)
--- a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
+++ b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
@@ -41,6 +41,9 @@ static bool panfrost_gem_purge(struct drm_gem_object *obj)
        struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
        struct panfrost_gem_object *bo = to_panfrost_bo(obj);
 
+       if (atomic_read(&bo->gpu_usecount))
+               return false;
+
        if (!mutex_trylock(&shmem->pages_lock))
                return false;
 

diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
index bbb0c5e..9f770d4 100644 (file)
--- a/drivers/gpu/drm/panfrost/panfrost_job.c
+++ b/drivers/gpu/drm/panfrost/panfrost_job.c
@@ -270,8 +270,13 @@ static void panfrost_job_cleanup(struct kref *ref)
        dma_fence_put(job->render_done_fence);
 
        if (job->mappings) {
-               for (i = 0; i < job->bo_count; i++)
+               for (i = 0; i < job->bo_count; i++) {
+                       if (!job->mappings[i])
+                               break;
+
+                       atomic_dec(&job->mappings[i]->obj->gpu_usecount);
                        panfrost_gem_mapping_put(job->mappings[i]);
+               }
                kvfree(job->mappings);
        }