[RFC 5/8] drm/i915: Keep track of registered clients indexed by task struct

[Tvrtko Ursulin]

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

A simple hash table of registered clients indexed by the task struct
pointer is kept to be used in a following patch.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursu...@intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_context.c |  2 ++
 drivers/gpu/drm/i915/i915_drm_client.c      | 31 ++++++++++++++++++++-
 drivers/gpu/drm/i915/i915_drm_client.h      | 13 +++++++++
 3 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c 
b/drivers/gpu/drm/i915/gem/i915_gem_context.c
index d1992ba59ed8..8d4d687ab1d0 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
@@ -1932,6 +1932,8 @@ int i915_gem_context_create_ioctl(struct drm_device *dev, 
void *data,
                return -EIO;
        }
 
+       i915_drm_client_update_owner(ext_data.fpriv->client, current);
+
        ext_data.pc = proto_context_create(i915, args->flags);
        if (IS_ERR(ext_data.pc))
                return PTR_ERR(ext_data.pc);
diff --git a/drivers/gpu/drm/i915/i915_drm_client.c 
b/drivers/gpu/drm/i915/i915_drm_client.c
index 91a8559bebf7..82b9636482ef 100644
--- a/drivers/gpu/drm/i915/i915_drm_client.c
+++ b/drivers/gpu/drm/i915/i915_drm_client.c
@@ -18,6 +18,9 @@ void i915_drm_clients_init(struct i915_drm_clients *clients,
        clients->next_id = 0;
 
        xa_init_flags(&clients->xarray, XA_FLAGS_ALLOC | XA_FLAGS_LOCK_IRQ);
+
+       rwlock_init(&clients->lock);
+       hash_init(clients->tasks);
 }
 
 struct i915_drm_client *i915_drm_client_add(struct i915_drm_clients *clients)
@@ -42,6 +45,8 @@ struct i915_drm_client *i915_drm_client_add(struct 
i915_drm_clients *clients)
        INIT_LIST_HEAD(&client->ctx_list);
        client->clients = clients;
 
+       i915_drm_client_update_owner(client, current);
+
        return client;
 
 err:
@@ -54,9 +59,14 @@ void __i915_drm_client_free(struct kref *kref)
 {
        struct i915_drm_client *client =
                container_of(kref, typeof(*client), kref);
-       struct xarray *xa = &client->clients->xarray;
+       struct i915_drm_clients *clients = client->clients;
+       struct xarray *xa = &clients->xarray;
        unsigned long flags;
 
+       write_lock(&clients->lock);
+       hash_del(&client->node);
+       write_unlock(&clients->lock);
+
        xa_lock_irqsave(xa, flags);
        __xa_erase(xa, client->id);
        xa_unlock_irqrestore(xa, flags);
@@ -68,3 +78,22 @@ void i915_drm_clients_fini(struct i915_drm_clients *clients)
        GEM_BUG_ON(!xa_empty(&clients->xarray));
        xa_destroy(&clients->xarray);
 }
+
+void i915_drm_client_update_owner(struct i915_drm_client *client,
+                                 struct task_struct *owner)
+{
+       struct i915_drm_clients *clients;
+
+       if (READ_ONCE(client->owner) == owner)
+               return;
+
+       clients = client->clients;
+       write_lock(&clients->lock);
+       if (READ_ONCE(client->owner) != owner) {
+               if (client->owner)
+                       hash_del(&client->node);
+               client->owner = owner;
+               hash_add(clients->tasks, &client->node, (uintptr_t)owner);
+       }
+       write_unlock(&clients->lock);
+}
diff --git a/drivers/gpu/drm/i915/i915_drm_client.h 
b/drivers/gpu/drm/i915/i915_drm_client.h
index 0207dfad4568..42fd79f0558a 100644
--- a/drivers/gpu/drm/i915/i915_drm_client.h
+++ b/drivers/gpu/drm/i915/i915_drm_client.h
@@ -6,8 +6,11 @@
 #ifndef __I915_DRM_CLIENT_H__
 #define __I915_DRM_CLIENT_H__
 
+#include <linux/hashtable.h>
 #include <linux/kref.h>
 #include <linux/list.h>
+#include <linux/rwlock.h>
+#include <linux/sched.h>
 #include <linux/spinlock.h>
 #include <linux/xarray.h>
 
@@ -18,6 +21,9 @@ struct i915_drm_clients {
 
        struct xarray xarray;
        u32 next_id;
+
+       rwlock_t lock;
+       DECLARE_HASHTABLE(tasks, 6);
 };
 
 struct i915_drm_client {
@@ -28,6 +34,9 @@ struct i915_drm_client {
        spinlock_t ctx_lock; /* For add/remove from ctx_list. */
        struct list_head ctx_list; /* List of contexts belonging to client. */
 
+       struct task_struct *owner; /* No reference kept, never dereferenced. */
+       struct hlist_node node;
+
        struct i915_drm_clients *clients;
 };
 
@@ -52,4 +61,8 @@ struct i915_drm_client *i915_drm_client_add(struct 
i915_drm_clients *clients);
 
 void i915_drm_clients_fini(struct i915_drm_clients *clients);
 
+void i915_drm_client_update_owner(struct i915_drm_client *client,
+                                 struct task_struct *owner);
+
+
 #endif /* !__I915_DRM_CLIENT_H__ */
-- 
2.30.2