[RFC 8/8] drm/i915: Connect with the process nice change notifier

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Connect i915 with the process nice change notifier so that our scheduling
can react to runtime adjustments, on top of previously added nice value
inheritance at context create time.

To achieve this we use the previously added map of clients per owning
tasks in combination with the list of GEM contexts per client.

To avoid possibly unnecessary complications the updated context nice value
will only apply to future submissions against the context.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
---
 drivers/gpu/drm/i915/i915_drm_client.c | 31 ++++++++++++++++++++++++++
 drivers/gpu/drm/i915/i915_drm_client.h |  3 +++
 2 files changed, 34 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drm_client.c b/drivers/gpu/drm/i915/i915_drm_client.c
index 82b9636482ef..e34c1228f65b 100644
--- a/drivers/gpu/drm/i915/i915_drm_client.c
+++ b/drivers/gpu/drm/i915/i915_drm_client.c
@@ -7,10 +7,35 @@
 #include <linux/slab.h>
 #include <linux/types.h>
 
+#include "gem/i915_gem_context.h"
 #include "i915_drm_client.h"
 #include "i915_gem.h"
 #include "i915_utils.h"
 
+static int
+clients_notify(struct notifier_block *nb, unsigned long val, void *ptr)
+{
+	struct i915_drm_clients *clients =
+		container_of(nb, typeof(*clients), prio_notifier);
+	struct i915_drm_client *client;
+
+	rcu_read_lock();
+	read_lock(&clients->lock);
+	hash_for_each_possible(clients->tasks, client, node, (uintptr_t)ptr) {
+		struct i915_gem_context *ctx;
+
+		if (client->owner != ptr)
+			continue;
+
+		list_for_each_entry_rcu(ctx, &client->ctx_list, client_link)
+			ctx->sched.nice = (int)val;
+	}
+	read_unlock(&clients->lock);
+	rcu_read_unlock();
+
+	return NOTIFY_DONE;
+}
+
 void i915_drm_clients_init(struct i915_drm_clients *clients,
 			   struct drm_i915_private *i915)
 {
@@ -21,6 +46,10 @@ void i915_drm_clients_init(struct i915_drm_clients *clients,
 
 	rwlock_init(&clients->lock);
 	hash_init(clients->tasks);
+
+	memset(&clients->prio_notifier, 0, sizeof(clients->prio_notifier));
+	clients->prio_notifier.notifier_call = clients_notify;
+	register_user_nice_notifier(&clients->prio_notifier);
 }
 
 struct i915_drm_client *i915_drm_client_add(struct i915_drm_clients *clients)
@@ -75,6 +104,8 @@ void __i915_drm_client_free(struct kref *kref)
 
 void i915_drm_clients_fini(struct i915_drm_clients *clients)
 {
+	unregister_user_nice_notifier(&clients->prio_notifier);
+
 	GEM_BUG_ON(!xa_empty(&clients->xarray));
 	xa_destroy(&clients->xarray);
 }
diff --git a/drivers/gpu/drm/i915/i915_drm_client.h b/drivers/gpu/drm/i915/i915_drm_client.h
index 42fd79f0558a..dda26aa42ac9 100644
--- a/drivers/gpu/drm/i915/i915_drm_client.h
+++ b/drivers/gpu/drm/i915/i915_drm_client.h
@@ -9,6 +9,7 @@
 #include <linux/hashtable.h>
 #include <linux/kref.h>
 #include <linux/list.h>
+#include <linux/notifier.h>
 #include <linux/rwlock.h>
 #include <linux/sched.h>
 #include <linux/spinlock.h>
@@ -24,6 +25,8 @@ struct i915_drm_clients {
 
 	rwlock_t lock;
 	DECLARE_HASHTABLE(tasks, 6);
+
+	struct notifier_block prio_notifier;
 };
 
 struct i915_drm_client {
-- 
2.30.2