| Message ID | 20230622083932.4090339-6-qi.zheng@linux.dev (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | use refcount+RCU method to implement lockless slab shrink | expand |
On 22/06/2023 09:39, Qi Zheng wrote: > From: Qi Zheng <zhengqi.arch@bytedance.com> > > In preparation for implementing lockless slab shrink, > we need 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 <zhengqi.arch@bytedance.com> > --- > drivers/gpu/drm/panfrost/panfrost_device.h | 2 +- > .../gpu/drm/panfrost/panfrost_gem_shrinker.c | 24 ++++++++++--------- > 2 files changed, 14 insertions(+), 12 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_gem_shrinker.c b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c > index bf0170782f25..2a5513eb9e1f 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; > > @@ -100,10 +98,15 @@ panfrost_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc) > void 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_and_init(panfrost_gem_shrinker_count, > + panfrost_gem_shrinker_scan, 0, > + DEFAULT_SEEKS, 0, pfdev); > + if (pfdev->shrinker && > + register_shrinker(pfdev->shrinker, "drm-panfrost")) { > + shrinker_free(pfdev->shrinker); > + WARN_ON(1); > + } So we didn't have good error handling here before, but this is significantly worse. Previously if register_shrinker() failed then the driver could safely continue without a shrinker - it would waste memory but still function. However we now have two failure conditions: * shrinker_alloc_init() returns NULL. No warning and NULL deferences will happen later. * register_shrinker() fails, shrinker_free() will free pdev->shrinker we get a warning, but followed by a use-after-free later. I think we need to modify panfrost_gem_shrinker_init() to be able to return an error, so a change something like the below (untested) before your change. Steve ----8<--- 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..90265b37636f 100644 --- a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c +++ b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c @@ -97,13 +97,17 @@ 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; + int ret; + 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")); + ret = register_shrinker(&pfdev->shrinker, "drm-panfrost"); + + return ret; } /**
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_gem_shrinker.c b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c index bf0170782f25..2a5513eb9e1f 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; @@ -100,10 +98,15 @@ panfrost_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc) void 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_and_init(panfrost_gem_shrinker_count, + panfrost_gem_shrinker_scan, 0, + DEFAULT_SEEKS, 0, pfdev); + if (pfdev->shrinker && + register_shrinker(pfdev->shrinker, "drm-panfrost")) { + shrinker_free(pfdev->shrinker); + WARN_ON(1); + } } /** @@ -116,7 +119,6 @@ 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->nr_deferred) + unregister_and_free_shrinker(pfdev->shrinker); }