[RFC 12/17] cgroup/drm: Client exit hook

[Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>]

From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>

We need the ability for DRM core to inform the cgroup controller when a
client has closed a DRM file descriptor. This will allow us not needing
to keep state relating to GPU time usage by tasks sets in the cgroup
controller itself.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
 drivers/gpu/drm/drm_cgroup.c | 8 ++++++++
 include/linux/cgroup_drm.h   | 1 +
 kernel/cgroup/drm.c          | 8 ++++++++
 3 files changed, 17 insertions(+)

diff --git a/drivers/gpu/drm/drm_cgroup.c b/drivers/gpu/drm/drm_cgroup.c
index e36bc4333924..ff99d1f4f1d4 100644
--- a/drivers/gpu/drm/drm_cgroup.c
+++ b/drivers/gpu/drm/drm_cgroup.c
@@ -5,6 +5,7 @@
 
 #include <drm/drm_drv.h>
 #include <drm/drm_clients.h>
+#include <linux/cgroup_drm.h>
 
 static DEFINE_XARRAY(drm_pid_clients);
 
@@ -25,6 +26,7 @@ void drm_clients_close(struct drm_file *file_priv)
 {
 	struct drm_device *dev = file_priv->minor->dev;
 	struct drm_pid_clients *clients;
+	struct task_struct *task;
 
 	lockdep_assert_held(&dev->filelist_mutex);
 
@@ -35,6 +37,12 @@ void drm_clients_close(struct drm_file *file_priv)
 	if (WARN_ON_ONCE(!clients))
 		return;
 
+	task = get_pid_task(file_priv->cpid, PIDTYPE_PID);
+	if (task) {
+		drmcgroup_client_exited(task);
+		put_task_struct(task);
+	}
+
 	__del_clients(clients, file_priv);
 
 	/*
diff --git a/include/linux/cgroup_drm.h b/include/linux/cgroup_drm.h
index 66063b4708e8..c84516d3e50a 100644
--- a/include/linux/cgroup_drm.h
+++ b/include/linux/cgroup_drm.h
@@ -13,5 +13,6 @@ struct task_struct;
 #define DRM_CGROUP_PRIORITY_MAX	(10000)
 
 int drmcgroup_lookup_effective_priority(struct task_struct *task);
+void drmcgroup_client_exited(struct task_struct *task);
 
 #endif	/* _CGROUP_DRM_H */
diff --git a/kernel/cgroup/drm.c b/kernel/cgroup/drm.c
index 4b6f88d8236e..48f1eaaa1c07 100644
--- a/kernel/cgroup/drm.c
+++ b/kernel/cgroup/drm.c
@@ -221,6 +221,14 @@ static void drmcs_attach(struct cgroup_taskset *tset)
 					css_to_drmcs(css)->effective_priority);
 }
 
+void drmcgroup_client_exited(struct task_struct *task)
+{
+	struct drm_cgroup_state *drmcs = get_task_drmcs(task);
+
+	css_put(&drmcs->css);
+}
+EXPORT_SYMBOL_GPL(drmcgroup_client_exited);
+
 static struct drm_cgroup_state root_drmcs = {
 	.priority = DRM_CGROUP_PRIORITY_DEF,
 	.effective_priority = DRM_CGROUP_PRIORITY_DEF,
-- 
2.34.1