Hi Steven,

On 2023/7/24 19:17, Steven Price wrote:

On 24/07/2023 10:43, Qi Zheng wrote:

quoted

In preparation for implementing lockless slab shrink, use new APIs to
dynamically allocate the drm-panfrost shrinker, so that it can be freed
asynchronously using kfree_rcu(). Then it doesn't need to wait for RCU
read-side critical section when releasing the struct panfrost_device.

Signed-off-by: Qi Zheng <redacted>

One nit below, but otherwise:

Reviewed-by: Steven Price <steven.price@arm.com>

quoted

---
  drivers/gpu/drm/panfrost/panfrost_device.h    |  2 +-
  drivers/gpu/drm/panfrost/panfrost_drv.c       |  6 +++-
  drivers/gpu/drm/panfrost/panfrost_gem.h       |  2 +-
  .../gpu/drm/panfrost/panfrost_gem_shrinker.c  | 32 ++++++++++++-------
  4 files changed, 27 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/panfrost/panfrost_device.h b/drivers/gpu/drm/panfrost/panfrost_device.h
index b0126b9fbadc..e667e5689353 100644
--- a/drivers/gpu/drm/panfrost/panfrost_device.h
+++ b/drivers/gpu/drm/panfrost/panfrost_device.h

@@ -118,7 +118,7 @@ struct panfrost_device {
  
  	struct mutex shrinker_lock;
  	struct list_head shrinker_list;
-	struct shrinker shrinker;
+	struct shrinker *shrinker;
  
  	struct panfrost_devfreq pfdevfreq;
  };

diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
index bbada731bbbd..f705bbdea360 100644
--- a/drivers/gpu/drm/panfrost/panfrost_drv.c
+++ b/drivers/gpu/drm/panfrost/panfrost_drv.c

@@ -598,10 +598,14 @@ static int panfrost_probe(struct platform_device *pdev)
  	if (err < 0)
  		goto err_out1;
  
-	panfrost_gem_shrinker_init(ddev);
+	err = panfrost_gem_shrinker_init(ddev);
+	if (err)
+		goto err_out2;
  
  	return 0;
  
+err_out2:
+	drm_dev_unregister(ddev);
  err_out1:
  	pm_runtime_disable(pfdev->dev);
  	panfrost_device_fini(pfdev);

diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.h b/drivers/gpu/drm/panfrost/panfrost_gem.h
index ad2877eeeccd..863d2ec8d4f0 100644
--- a/drivers/gpu/drm/panfrost/panfrost_gem.h
+++ b/drivers/gpu/drm/panfrost/panfrost_gem.h

@@ -81,7 +81,7 @@ panfrost_gem_mapping_get(struct panfrost_gem_object *bo,
  void panfrost_gem_mapping_put(struct panfrost_gem_mapping *mapping);
  void panfrost_gem_teardown_mappings_locked(struct panfrost_gem_object *bo);
  
-void panfrost_gem_shrinker_init(struct drm_device *dev);
+int panfrost_gem_shrinker_init(struct drm_device *dev);
  void panfrost_gem_shrinker_cleanup(struct drm_device *dev);
  
  #endif /* __PANFROST_GEM_H__ */

diff --git a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
index bf0170782f25..9a90dfb5301f 100644
--- a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
+++ b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c

@@ -18,8 +18,7 @@
  static unsigned long
  panfrost_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
  {
-	struct panfrost_device *pfdev =
-		container_of(shrinker, struct panfrost_device, shrinker);
+	struct panfrost_device *pfdev = shrinker->private_data;
  	struct drm_gem_shmem_object *shmem;
  	unsigned long count = 0;
  

@@ -65,8 +64,7 @@ static bool panfrost_gem_purge(struct drm_gem_object *obj)
  static unsigned long
  panfrost_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
  {
-	struct panfrost_device *pfdev =
-		container_of(shrinker, struct panfrost_device, shrinker);
+	struct panfrost_device *pfdev = shrinker->private_data;
  	struct drm_gem_shmem_object *shmem, *tmp;
  	unsigned long freed = 0;
  

@@ -97,13 +95,24 @@ panfrost_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
   *
   * This function registers and sets up the panfrost shrinker.
   */
-void panfrost_gem_shrinker_init(struct drm_device *dev)
+int panfrost_gem_shrinker_init(struct drm_device *dev)
  {
  	struct panfrost_device *pfdev = dev->dev_private;
-	pfdev->shrinker.count_objects = panfrost_gem_shrinker_count;
-	pfdev->shrinker.scan_objects = panfrost_gem_shrinker_scan;
-	pfdev->shrinker.seeks = DEFAULT_SEEKS;
-	WARN_ON(register_shrinker(&pfdev->shrinker, "drm-panfrost"));
+
+	pfdev->shrinker = shrinker_alloc(0, "drm-panfrost");
+	if (!pfdev->shrinker) {
+		WARN_ON(1);

I don't think this WARN_ON is particularly useful - if there's a failed
memory allocation we should see output from the kernel anyway. And we're
changing the semantics from "continue just without a shrinker" (which
argueably justifies the warning) to "probe fails, device doesn't work"
which will be obvious to the user so I don't feel we need the additional
warn.

Make sense. Will delete this WARN_ON() in the next version.

Thanks,
Qi

quoted

+		return -ENOMEM;
+	}
+
+	pfdev->shrinker->count_objects = panfrost_gem_shrinker_count;
+	pfdev->shrinker->scan_objects = panfrost_gem_shrinker_scan;
+	pfdev->shrinker->seeks = DEFAULT_SEEKS;
+	pfdev->shrinker->private_data = pfdev;
+
+	shrinker_register(pfdev->shrinker);
+
+	return 0;
  }
  
  /**

@@ -116,7 +125,6 @@ void panfrost_gem_shrinker_cleanup(struct drm_device *dev)
  {
  	struct panfrost_device *pfdev = dev->dev_private;
  
-	if (pfdev->shrinker.nr_deferred) {
-		unregister_shrinker(&pfdev->shrinker);
-	}
+	if (pfdev->shrinker)
+		shrinker_unregister(pfdev->shrinker);
  }