Sync block verification (#74)

* Synchronize block verification
* max_round_blocks_to_import set to 1
* Fixed test that rely on 12block batches

Co-authored-by: adria0.eth <5526331+adria0@users.noreply.github.com>

ethcore/src/client/client.rs

@@ -389,6 +389,8 @@ impl Importer {
 
         let db = client.db.read();
         db.key_value().flush().expect("DB flush failed.");
+
+        self.block_queue.resignal_verification();
         imported
     }
 

ethcore/src/client/config.rs

@@ -151,7 +151,7 @@ impl Default for ClientConfig {
             history_mem: 32 * mb,
             check_seal: true,
             transaction_verification_queue_size: 8192,
-            max_round_blocks_to_import: 12,
+            max_round_blocks_to_import: 1,
             snapshot: Default::default(),
         }
     }

ethcore/src/tests/client.rs

@@ -278,7 +278,7 @@ fn can_handle_long_fork() {
     push_blocks_to_client(&client, 49, 1201, 800);
     push_blocks_to_client(&client, 53, 1201, 600);
 
-    for _ in 0..400 {
+    for _ in 0..2300 {
         client.import_verified_blocks();
     }
     assert_eq!(2000, client.chain_info().best_block_number);

ethcore/src/verification/queue/mod.rs

@@ -665,11 +665,17 @@ impl<K: Kind> VerificationQueue<K> {
             .verified
             .fetch_sub(drained_size, AtomicOrdering::SeqCst);
 
+        result
+    }
+
+    /// release taken signal and call async ClientIoMessage::BlockVerified call to client so that it can continue verification.
+    /// difference between sync and async is whose thread pool is used.
+    pub fn resignal_verification(&self) {
+        let verified = self.verification.verified.lock();
         self.ready_signal.reset();
         if !verified.is_empty() {
             self.ready_signal.set_async();
         }
-        result
     }
 
     /// Returns true if there is nothing currently in the queue.