RFC 14: Improve locking mechanism for parachains (#1290)

* rfc14

* Update polkadot/runtime/common/src/paras_registrar/mod.rs

Co-authored-by: Bastian Köcher <git@kchr.de>

* Update polkadot/runtime/common/src/paras_registrar/mod.rs

Co-authored-by: Bastian Köcher <git@kchr.de>

* Update polkadot/runtime/common/src/paras_registrar/mod.rs

Co-authored-by: Bastian Köcher <git@kchr.de>

* fmt

* fix

* Update polkadot/runtime/common/src/paras_registrar/migration.rs

Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* fmt

* 2224 is unlocked

* update migration list

* update comment

* use VersionedMigration

---------

Co-authored-by: Bastian Köcher <git@kchr.de>
Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

polkadot/runtime/parachains/Cargo.toml

@@ -6,6 +6,7 @@ edition.workspace = true
 license.workspace = true
 
 [dependencies]
+impl-trait-for-tuples = "0.2.2"
 bitvec = { version = "1.0.0", default-features = false, features = ["alloc"] }
 parity-scale-codec = { version = "3.6.1", default-features = false, features = ["derive", "max-encoded-len"] }
 log = { version = "0.4.17", default-features = false }

polkadot/runtime/parachains/src/mock.rs

@@ -214,6 +214,7 @@ impl crate::paras::Config for Test {
 	type UnsignedPriority = ParasUnsignedPriority;
 	type QueueFootprinter = ParaInclusion;
 	type NextSessionRotation = TestNextSessionRotation;
+	type OnNewHead = ();
 }
 
 impl crate::dmp::Config for Test {}

polkadot/runtime/parachains/src/paras/mod.rs

@@ -481,6 +481,22 @@ impl<BlockNumber> PvfCheckActiveVoteState<BlockNumber> {
 	}
 }
 
+/// Runtime hook for when a parachain head is updated.
+pub trait OnNewHead {
+	/// Called when a parachain head is updated.
+	/// Returns the weight consumed by this function.
+	fn on_new_head(id: ParaId, head: &HeadData) -> Weight;
+}
+
+#[impl_trait_for_tuples::impl_for_tuples(30)]
+impl OnNewHead for Tuple {
+	fn on_new_head(id: ParaId, head: &HeadData) -> Weight {
+		let mut weight: Weight = Default::default();
+		for_tuples!( #( weight.saturating_accrue(Tuple::on_new_head(id, head)); )* );
+		weight
+	}
+}
+
 pub trait WeightInfo {
 	fn force_set_current_code(c: u32) -> Weight;
 	fn force_set_current_head(s: u32) -> Weight;
@@ -575,6 +591,9 @@ pub mod pallet {
 		/// be set to the `ParaInclusion` pallet.
 		type QueueFootprinter: QueueFootprinter<Origin = UmpQueueId>;
 
+		/// Runtime hook for when a parachain head is updated.
+		type OnNewHead: OnNewHead;
+
 		/// Weight information for extrinsics in this pallet.
 		type WeightInfo: WeightInfo;
 	}
@@ -1962,10 +1981,10 @@ impl<T: Config> Pallet<T> {
 		new_head: HeadData,
 		execution_context: BlockNumberFor<T>,
 	) -> Weight {
-		Heads::<T>::insert(&id, new_head);
+		Heads::<T>::insert(&id, &new_head);
 		MostRecentContext::<T>::insert(&id, execution_context);
 
-		if let Some(expected_at) = FutureCodeUpgrades::<T>::get(&id) {
+		let weight = if let Some(expected_at) = FutureCodeUpgrades::<T>::get(&id) {
 			if expected_at <= execution_context {
 				FutureCodeUpgrades::<T>::remove(&id);
 				UpgradeGoAheadSignal::<T>::remove(&id);
@@ -2005,7 +2024,9 @@ impl<T: Config> Pallet<T> {
 			// the `Abort` signal.
 			UpgradeGoAheadSignal::<T>::remove(&id);
 			T::DbWeight::get().reads_writes(1, 2)
-		}
+		};
+
+		weight.saturating_add(T::OnNewHead::on_new_head(id, &new_head))
 	}
 
 	/// Returns the list of PVFs (aka validation code) that require casting a vote by a validator in