drm/i915: Allow contexts to be unreferenced locklessly

If we move the actual cleanup of the context to a worker, we can allow
the final free to be called from any context and avoid undue latency in
the caller.

v2: Negotiate handling the delayed contexts free by flushing the
workqueue before calling i915_gem_context_fini() and performing the final
free of the kernel context directly
v3: Flush deferred frees before new context allocations

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170620110547.15947-2-chris@chris-wilson.co.uk

1 files changed, 14 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem_context.h b/drivers/gpu/drm/i915/i915_gem_context.h
index 808f878db812..61146f4aa168 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.h
+++ b/drivers/gpu/drm/i915/i915_gem_context.h
@@ -86,6 +86,7 @@ struct i915_gem_context {
 
 	/** link: place with &drm_i915_private.context_list */
 	struct list_head link;
+	struct llist_node free_link;
 
 	/**
 	 * @ref: reference count
@@ -284,7 +285,7 @@ void i915_gem_context_close(struct drm_file *file);
 int i915_switch_context(struct drm_i915_gem_request *req);
 int i915_gem_switch_to_kernel_context(struct drm_i915_private *dev_priv);
 
-void i915_gem_context_free(struct kref *ctx_ref);
+void i915_gem_context_release(struct kref *ctx_ref);
 struct i915_gem_context *
 i915_gem_context_create_gvt(struct drm_device *dev);
 
@@ -299,4 +300,16 @@ int i915_gem_context_setparam_ioctl(struct drm_device *dev, void *data,
 int i915_gem_context_reset_stats_ioctl(struct drm_device *dev, void *data,
 				       struct drm_file *file);
 
+static inline struct i915_gem_context *
+i915_gem_context_get(struct i915_gem_context *ctx)
+{
+	kref_get(&ctx->ref);
+	return ctx;
+}
+
+static inline void i915_gem_context_put(struct i915_gem_context *ctx)
+{
+	kref_put(&ctx->ref, i915_gem_context_release);
+}
+
 #endif /* !__I915_GEM_CONTEXT_H__ */