Re: [Intel-gfx] [PATCH 7/9] drm/i915/gt: Fix memory leaks in per-gt sysfs

[Andrzej Hajda]

Hi Ashutosh,

On 20.04.2022 07:21, Ashutosh Dixit wrote:
All kmalloc'd kobjects need a kobject_put() to free memory. For example in
previous code, kobj_gt_release() never gets called. The requirement of
kobject_put() now results in a slightly different code organization.
Cc: Andi Shyti <andi.sh...@intel.com>
Cc: Andrzej Hajda <andrzej.ha...@intel.com>
Cc: Rodrigo Vivi <rodrigo.v...@intel.com>
Fixes: b770bcfae9ad ("drm/i915/gt: create per-tile sysfs interface")
Signed-off-by: Ashutosh Dixit <ashutosh.di...@intel.com>
---
  drivers/gpu/drm/i915/gt/intel_gt.c       |  1 +
  drivers/gpu/drm/i915/gt/intel_gt_sysfs.c | 35 ++++++++++--------------
  drivers/gpu/drm/i915/gt/intel_gt_sysfs.h |  6 +---
  drivers/gpu/drm/i915/gt/intel_gt_types.h |  3 ++
  drivers/gpu/drm/i915/i915_sysfs.c        |  2 ++
  5 files changed, 22 insertions(+), 25 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c 
b/drivers/gpu/drm/i915/gt/intel_gt.c
index f0014c5072c9..f0c56ca12c0b 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt.c
@@ -783,6 +783,7 @@ void intel_gt_driver_unregister(struct intel_gt *gt)
  {
        intel_wakeref_t wakeref;
  
+	intel_gt_sysfs_unregister(gt);
        intel_rps_driver_unregister(&gt->rps);
  
  	intel_pxp_fini(&gt->pxp);
diff --git a/drivers/gpu/drm/i915/gt/intel_gt_sysfs.c 
b/drivers/gpu/drm/i915/gt/intel_gt_sysfs.c
index 8ec8bc660c8c..6f1b081ca5b7 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt_sysfs.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt_sysfs.c
@@ -24,7 +24,7 @@ bool is_object_gt(struct kobject *kobj)
  
  static struct intel_gt *kobj_to_gt(struct kobject *kobj)
  {
-       return container_of(kobj, struct kobj_gt, base)->gt;
+       return container_of(kobj, struct intel_gt, sysfs_gtn);
  }
  
  struct intel_gt *intel_gt_sysfs_get_drvdata(struct device *dev,
@@ -72,21 +72,19 @@ static struct attribute *id_attrs[] = {
  };
  ATTRIBUTE_GROUPS(id);
  
-static void kobj_gt_release(struct kobject *kobj)
+/* A kobject needs a release() method even if it does nothing */
+static void kobj_gtn_release(struct kobject *kobj)
  {
-       kfree(kobj);
  }
  
-static struct kobj_type kobj_gt_type = {
-       .release = kobj_gt_release,
+static struct kobj_type kobj_gtn_type = {
+       .release = kobj_gtn_release,
        .sysfs_ops = &kobj_sysfs_ops,
        .default_groups = id_groups,
  };
  
  void intel_gt_sysfs_register(struct intel_gt *gt)
  {
-       struct kobj_gt *kg;
-
        /*
         * We need to make things right with the
         * ABI compatibility. The files were originally
@@ -98,25 +96,22 @@ void intel_gt_sysfs_register(struct intel_gt *gt)
        if (gt_is_root(gt))
                intel_gt_sysfs_pm_init(gt, gt_get_parent_obj(gt));
  
-	kg = kzalloc(sizeof(*kg), GFP_KERNEL);
-       if (!kg)
+       /* init and xfer ownership to sysfs tree */
+       if (kobject_init_and_add(&gt->sysfs_gtn, &kobj_gtn_type,
+                                gt->i915->sysfs_gt, "gt%d", gt->info.id))
                goto exit_fail;
  
-	kobject_init(&kg->base, &kobj_gt_type);
-       kg->gt = gt;
-
-       /* xfer ownership to sysfs tree */
-       if (kobject_add(&kg->base, gt->i915->sysfs_gt, "gt%d", gt->info.id))
-               goto exit_kobj_put;
-
-       intel_gt_sysfs_pm_init(gt, &kg->base);
+       intel_gt_sysfs_pm_init(gt, &gt->sysfs_gtn);
  
  	return;
  
-exit_kobj_put:
-       kobject_put(&kg->base);
-
  exit_fail:
+       kobject_put(&gt->sysfs_gtn);
        drm_warn(&gt->i915->drm,
                 "failed to initialize gt%d sysfs root\n", gt->info.id);
  }
+
+void intel_gt_sysfs_unregister(struct intel_gt *gt)
+{
+       kobject_put(&gt->sysfs_gtn);
+}
diff --git a/drivers/gpu/drm/i915/gt/intel_gt_sysfs.h 
b/drivers/gpu/drm/i915/gt/intel_gt_sysfs.h
index 9471b26752cf..a99aa7e8b01a 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt_sysfs.h
+++ b/drivers/gpu/drm/i915/gt/intel_gt_sysfs.h
@@ -13,11 +13,6 @@
  
  struct intel_gt;
  
-struct kobj_gt {
-       struct kobject base;
-       struct intel_gt *gt;
-};
-
  bool is_object_gt(struct kobject *kobj);
  
  struct drm_i915_private *kobj_to_i915(struct kobject *kobj);
@@ -28,6 +23,7 @@ intel_gt_create_kobj(struct intel_gt *gt,
                     const char *name);
  
  void intel_gt_sysfs_register(struct intel_gt *gt);
+void intel_gt_sysfs_unregister(struct intel_gt *gt);
  struct intel_gt *intel_gt_sysfs_get_drvdata(struct device *dev,
                                            const char *name);
  
diff --git a/drivers/gpu/drm/i915/gt/intel_gt_types.h b/drivers/gpu/drm/i915/gt/intel_gt_types.h
index 937b2e1a305e..4c72b4f983a6 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt_types.h
+++ b/drivers/gpu/drm/i915/gt/intel_gt_types.h
@@ -222,6 +222,9 @@ struct intel_gt {
        } mocs;
  
  	struct intel_pxp pxp;
+
+       /* gt/gtN sysfs */
+       struct kobject sysfs_gtn;

If you put kobject as a part of intel_gt what assures you that lifetime 
of kobject is shorter than intel_gt? Ie its refcounter is 0 on removal 
of intel_gt?

Regards
Andrzej

  };
  
  enum intel_gt_scratch_field {
diff --git a/drivers/gpu/drm/i915/i915_sysfs.c 
b/drivers/gpu/drm/i915/i915_sysfs.c
index 8521daba212a..3f06106cdcf5 100644
--- a/drivers/gpu/drm/i915/i915_sysfs.c
+++ b/drivers/gpu/drm/i915/i915_sysfs.c
@@ -259,4 +259,6 @@ void i915_teardown_sysfs(struct drm_i915_private *dev_priv)
  
  	device_remove_bin_file(kdev,  &dpf_attrs_1);
        device_remove_bin_file(kdev,  &dpf_attrs);
+
+       kobject_put(dev_priv->sysfs_gt);
  }