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Message-ID: <cdd08c9e-81d3-a85f-5426-5db738aa73ec@arm.com>
Date: Mon, 24 Jul 2023 12:17:40 +0100
From: Steven Price <steven.price@....com>
To: Qi Zheng <zhengqi.arch@...edance.com>, akpm@...ux-foundation.org,
david@...morbit.com, tkhai@...ru, vbabka@...e.cz, roman.gushchin@...ux.dev,
djwong@...nel.org, brauner@...nel.org, paulmck@...nel.org, tytso@....edu,
cel@...nel.org, senozhatsky@...omium.org, yujie.liu@...el.com,
gregkh@...uxfoundation.org, muchun.song@...ux.dev
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org,
kvm@...r.kernel.org, xen-devel@...ts.xenproject.org,
linux-erofs@...ts.ozlabs.org, linux-f2fs-devel@...ts.sourceforge.net,
cluster-devel@...hat.com, linux-nfs@...r.kernel.org,
linux-mtd@...ts.infradead.org, rcu@...r.kernel.org, netdev@...r.kernel.org,
dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
dm-devel@...hat.com, linux-raid@...r.kernel.org,
linux-bcache@...r.kernel.org, virtualization@...ts.linux-foundation.org,
linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
linux-xfs@...r.kernel.org, linux-btrfs@...r.kernel.org
Subject: Re: [PATCH v2 24/47] drm/panfrost: dynamically allocate the
drm-panfrost shrinker
On 24/07/2023 10:43, Qi Zheng wrote:
> 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 <zhengqi.arch@...edance.com>
One nit below, but otherwise:
Reviewed-by: Steven Price <steven.price@....com>
> ---
> 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.
> + 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);
> }
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