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Date: Thu, 20 Oct 2022 08:40:28 +0200
From: Christian König <christian.koenig@....com>
To: Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
Intel-gfx@...ts.freedesktop.org
Cc: cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
Tejun Heo <tj@...nel.org>,
Johannes Weiner <hannes@...xchg.org>,
Zefan Li <lizefan.x@...edance.com>,
Dave Airlie <airlied@...hat.com>,
Daniel Vetter <daniel.vetter@...ll.ch>,
Rob Clark <robdclark@...omium.org>,
Stéphane Marchesin <marcheu@...omium.org>,
"T . J . Mercier" <tjmercier@...gle.com>, Kenny.Ho@....com,
Brian Welty <brian.welty@...el.com>,
Tvrtko Ursulin <tvrtko.ursulin@...el.com>
Subject: Re: [RFC 02/17] drm: Track clients per owning process
Am 19.10.22 um 19:32 schrieb Tvrtko Ursulin:
> From: Tvrtko Ursulin <tvrtko.ursulin@...el.com>
>
> To enable propagation of settings from the cgroup drm controller to drm we
> need to start tracking which processes own which drm clients.
>
> Implement that by tracking the struct pid pointer of the owning process in
> a new XArray, pointing to a structure containing a list of associated
> struct drm_file pointers.
>
> Clients are added and removed under the filelist mutex and RCU list
> operations are used below it to allow for lockless lookup.
That won't work easily like this. The problem is that file_priv->pid is
usually not accurate these days:
From the debugfs clients file:
systemd-logind 773 0 y y 0 0
Xorg 1639 128 n n 1000 0
Xorg 1639 128 n n 1000 0
Xorg 1639 128 n n 1000 0
firefox 2945 128 n n 1000 0
Xorg 1639 128 n n 1000 0
Xorg 1639 128 n n 1000 0
Xorg 1639 128 n n 1000 0
Xorg 1639 128 n n 1000 0
chrome 35940 128 n n 1000 0
chrome 35940 0 n y 1000 1
chrome 35940 0 n y 1000 2
Xorg 1639 128 n n 1000 0
Xorg 1639 128 n n 1000 0
Xorg 1639 128 n n 1000 0
This is with glxgears and a bunch other OpenGL applications running.
The problem is that for most applications the X/Wayland server is now
opening the render node. The only exceptions in this case are apps using
DRI2 (VA-API?).
I always wanted to fix this and actually track who is using the file
descriptor instead of who opened it, but never had the time to do this.
I think you need to fix this problem first. And BTW: and unsigned long
doesn't work as PID either with containers.
Regards,
Christian.
>
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@...el.com>
> ---
> drivers/gpu/drm/Makefile | 1 +
> drivers/gpu/drm/drm_cgroup.c | 60 ++++++++++++++++++++++++++++++++++++
> drivers/gpu/drm/drm_file.c | 18 ++++++++---
> include/drm/drm_clients.h | 31 +++++++++++++++++++
> include/drm/drm_file.h | 4 +++
> 5 files changed, 110 insertions(+), 4 deletions(-)
> create mode 100644 drivers/gpu/drm/drm_cgroup.c
> create mode 100644 include/drm/drm_clients.h
>
> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
> index 6e55c47288e4..0719970d17ee 100644
> --- a/drivers/gpu/drm/Makefile
> +++ b/drivers/gpu/drm/Makefile
> @@ -59,6 +59,7 @@ drm-$(CONFIG_DRM_LEGACY) += \
> drm_scatter.o \
> drm_vm.o
> drm-$(CONFIG_DRM_LIB_RANDOM) += lib/drm_random.o
> +drm-$(CONFIG_CGROUP_DRM) += drm_cgroup.o
> drm-$(CONFIG_COMPAT) += drm_ioc32.o
> drm-$(CONFIG_DRM_PANEL) += drm_panel.o
> drm-$(CONFIG_OF) += drm_of.o
> diff --git a/drivers/gpu/drm/drm_cgroup.c b/drivers/gpu/drm/drm_cgroup.c
> new file mode 100644
> index 000000000000..a31ff1d593ab
> --- /dev/null
> +++ b/drivers/gpu/drm/drm_cgroup.c
> @@ -0,0 +1,60 @@
> +/* SPDX-License-Identifier: MIT */
> +/*
> + * Copyright © 2022 Intel Corporation
> + */
> +
> +#include <drm/drm_drv.h>
> +#include <drm/drm_clients.h>
> +
> +static DEFINE_XARRAY(drm_pid_clients);
> +
> +void drm_clients_close(struct drm_file *file_priv)
> +{
> + unsigned long pid = (unsigned long)file_priv->pid;
> + struct drm_device *dev = file_priv->minor->dev;
> + struct drm_pid_clients *clients;
> +
> + lockdep_assert_held(&dev->filelist_mutex);
> +
> + clients = xa_load(&drm_pid_clients, pid);
> + list_del_rcu(&file_priv->clink);
> + if (atomic_dec_and_test(&clients->num)) {
> + xa_erase(&drm_pid_clients, pid);
> + kfree_rcu(clients, rcu);
> + }
> +}
> +
> +int drm_clients_open(struct drm_file *file_priv)
> +{
> + unsigned long pid = (unsigned long)file_priv->pid;
> + struct drm_device *dev = file_priv->minor->dev;
> + struct drm_pid_clients *clients;
> + bool new_client = false;
> +
> + lockdep_assert_held(&dev->filelist_mutex);
> +
> + clients = xa_load(&drm_pid_clients, pid);
> + if (!clients) {
> + clients = kmalloc(sizeof(*clients), GFP_KERNEL);
> + if (!clients)
> + return -ENOMEM;
> + atomic_set(&clients->num, 0);
> + INIT_LIST_HEAD(&clients->file_list);
> + init_rcu_head(&clients->rcu);
> + new_client = true;
> + }
> + atomic_inc(&clients->num);
> + list_add_tail_rcu(&file_priv->clink, &clients->file_list);
> + if (new_client) {
> + void *xret;
> +
> + xret = xa_store(&drm_pid_clients, pid, clients, GFP_KERNEL);
> + if (xa_err(xret)) {
> + list_del_init(&file_priv->clink);
> + kfree(clients);
> + return PTR_ERR(clients);
> + }
> + }
> +
> + return 0;
> +}
> diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
> index a8b4d918e9a3..ce58d5c513db 100644
> --- a/drivers/gpu/drm/drm_file.c
> +++ b/drivers/gpu/drm/drm_file.c
> @@ -40,6 +40,7 @@
> #include <linux/slab.h>
>
> #include <drm/drm_client.h>
> +#include <drm/drm_clients.h>
> #include <drm/drm_drv.h>
> #include <drm/drm_file.h>
> #include <drm/drm_print.h>
> @@ -298,6 +299,7 @@ static void drm_close_helper(struct file *filp)
>
> mutex_lock(&dev->filelist_mutex);
> list_del(&file_priv->lhead);
> + drm_clients_close(file_priv);
> mutex_unlock(&dev->filelist_mutex);
>
> drm_file_free(file_priv);
> @@ -349,10 +351,8 @@ static int drm_open_helper(struct file *filp, struct drm_minor *minor)
>
> if (drm_is_primary_client(priv)) {
> ret = drm_master_open(priv);
> - if (ret) {
> - drm_file_free(priv);
> - return ret;
> - }
> + if (ret)
> + goto err_free;
> }
>
> filp->private_data = priv;
> @@ -360,6 +360,9 @@ static int drm_open_helper(struct file *filp, struct drm_minor *minor)
> priv->filp = filp;
>
> mutex_lock(&dev->filelist_mutex);
> + ret = drm_clients_open(priv);
> + if (ret)
> + goto err_unlock;
> list_add(&priv->lhead, &dev->filelist);
> mutex_unlock(&dev->filelist_mutex);
>
> @@ -387,6 +390,13 @@ static int drm_open_helper(struct file *filp, struct drm_minor *minor)
> #endif
>
> return 0;
> +
> +err_unlock:
> + mutex_unlock(&dev->filelist_mutex);
> +err_free:
> + drm_file_free(priv);
> +
> + return ret;
> }
>
> /**
> diff --git a/include/drm/drm_clients.h b/include/drm/drm_clients.h
> new file mode 100644
> index 000000000000..4ae553a03d1e
> --- /dev/null
> +++ b/include/drm/drm_clients.h
> @@ -0,0 +1,31 @@
> +/* SPDX-License-Identifier: MIT */
> +/*
> + * Copyright © 2022 Intel Corporation
> + */
> +
> +#ifndef _DRM_CLIENTS_H_
> +#define _DRM_CLIENTS_H_
> +
> +#include <drm/drm_file.h>
> +
> +struct drm_pid_clients {
> + atomic_t num;
> + struct list_head file_list;
> + struct rcu_head rcu;
> +};
> +
> +#if IS_ENABLED(CONFIG_CGROUP_DRM)
> +void drm_clients_close(struct drm_file *file_priv);
> +int drm_clients_open(struct drm_file *file_priv);
> +#else
> +static inline void drm_clients_close(struct drm_file *file_priv)
> +{
> +}
> +
> +static inline int drm_clients_open(struct drm_file *file_priv)
> +{
> + return 0;
> +}
> +#endif
> +
> +#endif
> diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h
> index d780fd151789..0965eb111f24 100644
> --- a/include/drm/drm_file.h
> +++ b/include/drm/drm_file.h
> @@ -268,6 +268,10 @@ struct drm_file {
> /** @minor: &struct drm_minor for this file. */
> struct drm_minor *minor;
>
> +#if IS_ENABLED(CONFIG_CGROUP_DRM)
> + struct list_head clink;
> +#endif
> +
> /**
> * @object_idr:
> *
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