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, 2 insertions, 21 deletions

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index fb627df..0f1330a 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2315,6 +2315,8 @@ struct drm_i915_private {
 
 	struct {
 		struct list_head list;
+		struct llist_head free_list;
+		struct work_struct free_work;
 
 		/* The hw wants to have a stable context identifier for the
 		 * lifetime of the context (for OA, PASID, faults, etc).
@@ -3545,27 +3547,6 @@ i915_gem_context_lookup(struct drm_i915_file_private *file_priv, u32 id)
 	return ctx;
 }
 
-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)
-{
-	lockdep_assert_held(&ctx->i915->drm.struct_mutex);
-	kref_put(&ctx->ref, i915_gem_context_free);
-}
-
-static inline void i915_gem_context_put_unlocked(struct i915_gem_context *ctx)
-{
-	struct mutex *lock = &ctx->i915->drm.struct_mutex;
-
-	if (kref_put_mutex(&ctx->ref, i915_gem_context_free, lock))
-		mutex_unlock(lock);
-}
-
 static inline struct intel_timeline *
 i915_gem_context_lookup_timeline(struct i915_gem_context *ctx,
 				 struct intel_engine_cs *engine)