Revert "Tweak usage of mutexes to reduce chance of deadlocks"

This reverts commit f35166ce78.

src/lib.rs

@@ -41,6 +41,7 @@ fn derive_protocol(input: proc_macro2::TokenStream) -> proc_macro2::TokenStream
     let answer_enum_name = format_ident!("__{}Answer", name);
     let question_enum_name = format_ident!("__{}Question", name);
     let query_enum_name = format_ident!("__{}Query", name);
+    let queries_struct_name = format_ident!("__{}Queries", name);
     let client_connection_struct_name = format_ident!("__{}Connection", name);
     let server_trait_name = format_ident!("{}ServerTrait", name);
     let client_struct_name = format_ident!("{}Client", name);
@@ -176,6 +177,40 @@ fn derive_protocol(input: proc_macro2::TokenStream) -> proc_macro2::TokenStream
             #(#server_trait)*
         }
     };
+    // Create a struct to hold queries behind an Arc<Mutex<>> to enable async access
+    // TODO: It might be a good idea to just make this a generic struct and write it in actual code
+    // rather than in this macro
+    let queries_struct = quote! {
+        #[derive(Clone)]
+        struct #queries_struct_name {
+            queries: ::std::sync::Arc<::std::sync::Mutex<::std::collections::HashMap<u64, #query_enum_name>>>,
+        }
+        impl #queries_struct_name {
+            fn new() -> Self {
+                Self {
+                    queries: ::std::sync::Arc::new(::std::sync::Mutex::new(::std::collections::HashMap::new())),
+                }
+            }
+
+            pub fn insert(&self, nonce: u64, query: #query_enum_name) {
+                self.queries.lock().unwrap().insert(nonce, query);
+            }
+
+            pub fn get(&self, nonce: &u64) -> Option<#query_enum_name> {
+                self.queries.lock().unwrap().get(nonce).cloned()
+            }
+
+            pub fn set_answer(&self, nonce: u64, answer: #answer_enum_name) {
+                if let Some(query) = self.queries.lock().unwrap().get_mut(&nonce) {
+                    query.set_answer(answer);
+                }
+            }
+
+            pub fn len(&self) -> usize {
+                self.queries.lock().unwrap().len()
+            }
+        }
+    };
     // Create a struct to handle the connection from the client to the server
     let stream_type = quote! { tokio::net::TcpStream }; // TODO: In the future we could support other stream types
     let cc_struct = quote! {
@@ -248,24 +283,24 @@ fn derive_protocol(input: proc_macro2::TokenStream) -> proc_macro2::TokenStream
         }
         #[derive(Clone)]
         #vis struct #client_struct_name {
-            queries: ::std::sync::Arc<::tokio::sync::Mutex<::std::collections::HashMap<u64, #query_enum_name>>>,
+            queries: #queries_struct_name,
             send_queue: tokio::sync::mpsc::Sender<(u64, #question_enum_name)>,
             recv_queue: #client_recv_queue_wrapper,
         }
         impl #client_struct_name {
             pub fn new(send_queue: tokio::sync::mpsc::Sender<(u64, #question_enum_name)>, recv_queue: tokio::sync::mpsc::Receiver<(u64, #answer_enum_name)>) -> Self {
                 Self {
-                    queries: ::std::sync::Arc::new(::tokio::sync::Mutex::new(::std::collections::HashMap::new())),
+                    queries: #queries_struct_name::new(),
                     recv_queue: #client_recv_queue_wrapper::new(recv_queue),
                     send_queue,
                 }
             }
             async fn send(&self, query: #question_enum_name) -> Result<u64, #error_enum_name> {
-                let nonce = self.queries.lock().await.len() as u64;
+                let nonce = self.queries.len() as u64;
                 let res = self.send_queue.send((nonce, query.clone())).await;
                 match res {
                     Ok(_) => {
-                        self.queries.lock().await.insert(nonce, query.into());
+                        self.queries.insert(nonce, query.into());
                         Ok(nonce)
                     }
                     Err(e) => Err(#error_enum_name::SendError(e)),
@@ -273,18 +308,15 @@ fn derive_protocol(input: proc_macro2::TokenStream) -> proc_macro2::TokenStream
             }
             async fn recv_until(&self, id: u64) -> Result<#answer_enum_name, #error_enum_name> {
                 loop {
-                    let mut queries = self.queries.lock().await;
                     // Check if we've received the answer for the query we're looking for
-                    if let Some(query) = queries.get(&id) {
+                    if let Some(query) = self.queries.get(&id) {
                         if let Some(answer) = query.get_answer() {
                             return Ok(answer);
                         }
                     }
                     match self.recv_queue.recv().await {
                         Some((nonce, answer)) => {
-                            if let Some(query) = queries.get_mut(&nonce) {
-                                query.set_answer(answer.clone());
-                            }
+                            self.queries.set_answer(nonce, answer.clone());
                         }
                         None => return Err(#error_enum_name::Closed),
                     };
@@ -299,6 +331,7 @@ fn derive_protocol(input: proc_macro2::TokenStream) -> proc_macro2::TokenStream
         #answer_enum
         #question_enum
         #query_enum
+        #queries_struct
         #server_trait
         #cc_struct
         #client_struct