redo locking api

patch-db/src/handle.rs

@@ -7,10 +7,7 @@ use serde::{Deserialize, Serialize};
 use serde_json::Value;
 use tokio::sync::{broadcast::Receiver, RwLock, RwLockReadGuard};
 
-use crate::{
-    locker::{LockType, LockerGuard},
-    Locker, PatchDb, Revision, Store, Transaction,
-};
+use crate::{locker::LockerGuard, Locker, PatchDb, Revision, Store, Transaction};
 use crate::{patch::DiffPatch, Error};
 
 #[async_trait]
@@ -19,7 +16,7 @@ pub trait DbHandle: Send + Sync {
     fn rebase(&mut self) -> Result<(), Error>;
     fn store(&self) -> Arc<RwLock<Store>>;
     fn subscribe(&self) -> Receiver<Arc<Revision>>;
-    fn locker_and_locks(&mut self) -> (&Locker, Vec<&mut [(JsonPointer, LockerGuard)]>);
+    fn locker_and_locks(&mut self) -> (&Locker, Vec<&mut [(JsonPointer, Option<LockerGuard>)]>);
     async fn exists<S: AsRef<str> + Send + Sync, V: SegList + Send + Sync>(
         &mut self,
         ptr: &JsonPointer<S, V>,
@@ -41,12 +38,7 @@ pub trait DbHandle: Send + Sync {
         value: &Value,
     ) -> Result<Option<Arc<Revision>>, Error>;
     async fn apply(&mut self, patch: DiffPatch) -> Result<Option<Arc<Revision>>, Error>;
-    async fn lock<S: AsRef<str> + Clone + Send + Sync, V: SegList + Clone + Send + Sync>(
-        &mut self,
-        ptr: &JsonPointer<S, V>,
-        lock: LockType,
-        deep: bool,
-    ) -> ();
+    async fn lock(&mut self, ptr: &JsonPointer) -> ();
     async fn get<
         T: for<'de> Deserialize<'de>,
         S: AsRef<str> + Send + Sync,
@@ -90,7 +82,7 @@ impl<Handle: DbHandle + ?Sized> DbHandle for &mut Handle {
     fn subscribe(&self) -> Receiver<Arc<Revision>> {
         (**self).subscribe()
     }
-    fn locker_and_locks(&mut self) -> (&Locker, Vec<&mut [(JsonPointer, LockerGuard)]>) {
+    fn locker_and_locks(&mut self) -> (&Locker, Vec<&mut [(JsonPointer, Option<LockerGuard>)]>) {
         (*self).locker_and_locks()
     }
     async fn exists<S: AsRef<str> + Send + Sync, V: SegList + Send + Sync>(
@@ -124,13 +116,8 @@ impl<Handle: DbHandle + ?Sized> DbHandle for &mut Handle {
     async fn apply(&mut self, patch: DiffPatch) -> Result<Option<Arc<Revision>>, Error> {
         (*self).apply(patch).await
     }
-    async fn lock<S: AsRef<str> + Clone + Send + Sync, V: SegList + Clone + Send + Sync>(
-        &mut self,
-        ptr: &JsonPointer<S, V>,
-        lock: LockType,
-        deep: bool,
-    ) {
-        (*self).lock(ptr, lock, deep).await
+    async fn lock(&mut self, ptr: &JsonPointer) {
+        (*self).lock(ptr).await
     }
     async fn get<
         T: for<'de> Deserialize<'de>,
@@ -157,7 +144,7 @@ impl<Handle: DbHandle + ?Sized> DbHandle for &mut Handle {
 
 pub struct PatchDbHandle {
     pub(crate) db: PatchDb,
-    pub(crate) locks: Vec<(JsonPointer, LockerGuard)>,
+    pub(crate) locks: Vec<(JsonPointer, Option<LockerGuard>)>,
 }
 
 #[async_trait]
@@ -179,7 +166,7 @@ impl DbHandle for PatchDbHandle {
     fn subscribe(&self) -> Receiver<Arc<Revision>> {
         self.db.subscribe()
     }
-    fn locker_and_locks(&mut self) -> (&Locker, Vec<&mut [(JsonPointer, LockerGuard)]>) {
+    fn locker_and_locks(&mut self) -> (&Locker, Vec<&mut [(JsonPointer, Option<LockerGuard>)]>) {
         (&self.db.locker, vec![self.locks.as_mut_slice()])
     }
     async fn exists<S: AsRef<str> + Send + Sync, V: SegList + Send + Sync>(
@@ -225,27 +212,8 @@ impl DbHandle for PatchDbHandle {
     async fn apply(&mut self, patch: DiffPatch) -> Result<Option<Arc<Revision>>, Error> {
         self.db.apply(patch, None, None).await
     }
-    async fn lock<S: AsRef<str> + Clone + Send + Sync, V: SegList + Clone + Send + Sync>(
-        &mut self,
-        ptr: &JsonPointer<S, V>,
-        lock: LockType,
-        deep: bool,
-    ) {
-        match lock {
-            LockType::Read => {
-                self.db
-                    .locker
-                    .add_read_lock(ptr, &mut self.locks, &mut [], deep)
-                    .await;
-            }
-            LockType::Write => {
-                self.db
-                    .locker
-                    .add_write_lock(ptr, &mut self.locks, &mut [], deep)
-                    .await;
-            }
-            LockType::None => (),
-        }
+    async fn lock(&mut self, ptr: &JsonPointer) {
+        self.db.locker.add_lock(ptr, &mut self.locks, &mut []).await;
     }
     async fn get<
         T: for<'de> Deserialize<'de>,

patch-db/src/lib.rs

@@ -20,7 +20,7 @@ mod test;
 pub use handle::{DbHandle, PatchDbHandle};
 pub use json_patch;
 pub use json_ptr;
-pub use locker::{LockType, Locker};
+pub use locker::Locker;
 pub use model::{
     BoxModel, HasModel, Map, MapModel, Model, ModelData, ModelDataMut, OptionModel, VecModel,
 };

patch-db/src/locker.rs

@@ -1,250 +1,162 @@
+use std::borrow::Cow;
 use std::collections::HashMap;
-use std::sync::Arc;
+use std::sync::{Arc, Weak};
+use std::task::Poll;
 
-use futures::{future::BoxFuture, FutureExt};
+use futures::future::BoxFuture;
+use futures::FutureExt;
 use json_ptr::{JsonPointer, SegList};
-use qutex::{QrwLock, ReadGuard, WriteGuard};
+use qutex::{Guard, Qutex};
+use tokio::runtime::Handle;
 use tokio::sync::Mutex;
+use tokio::sync::Notify;
 
-#[derive(Debug, Clone, Copy)]
-pub enum LockType {
-    None,
-    Read,
-    Write,
-}
+#[derive(Debug)]
+pub struct LockerGuard(Arc<NotifyGuard>, Guard<()>, Arc<LockerInner>);
 
-pub enum LockerGuard {
-    Empty,
-    Read(LockerReadGuard),
-    Write(LockerWriteGuard),
-}
-impl LockerGuard {
-    pub fn take(&mut self) -> Self {
-        std::mem::replace(self, LockerGuard::Empty)
-    }
-}
-
-#[derive(Debug, Clone)]
-pub struct LockerReadGuard(Arc<Mutex<Option<ReadGuard<HashMap<String, Locker>>>>>);
-impl LockerReadGuard {
-    async fn upgrade(&self) -> Option<LockerWriteGuard> {
-        let guard = self.0.try_lock().unwrap().take();
-        if let Some(g) = guard {
-            Some(LockerWriteGuard(
-                Some(ReadGuard::upgrade(g).await.unwrap()),
-                Some(self.clone()),
-            ))
-        } else {
-            None
-        }
-    }
-}
-impl From<ReadGuard<HashMap<String, Locker>>> for LockerReadGuard {
-    fn from(guard: ReadGuard<HashMap<String, Locker>>) -> Self {
-        LockerReadGuard(Arc::new(Mutex::new(Some(guard))))
-    }
-}
-
-pub struct LockerWriteGuard(
-    Option<WriteGuard<HashMap<String, Locker>>>,
-    Option<LockerReadGuard>,
-);
-impl From<WriteGuard<HashMap<String, Locker>>> for LockerWriteGuard {
-    fn from(guard: WriteGuard<HashMap<String, Locker>>) -> Self {
-        LockerWriteGuard(Some(guard), None)
-    }
-}
-impl Drop for LockerWriteGuard {
+#[derive(Debug)]
+struct NotifyGuard(Arc<Notify>);
+impl Drop for NotifyGuard {
     fn drop(&mut self) {
-        if let (Some(write), Some(read)) = (self.0.take(), self.1.take()) {
-            *read.0.try_lock().unwrap() = Some(WriteGuard::downgrade(write));
-        }
+        self.0.notify_one();
     }
 }
 
-#[derive(Clone, Debug)]
-pub struct Locker(QrwLock<HashMap<String, Locker>>);
+#[derive(Debug)]
+pub struct Locker(Arc<LockerInner>);
+#[derive(Debug)]
+struct LockerInner {
+    map: Mutex<HashMap<String, Weak<LockerInner>>>,
+    self_lock: Qutex<()>,
+    children_lock: Arc<Notify>,
+    guard: Mutex<Weak<NotifyGuard>>,
+    parent: Option<(Arc<NotifyGuard>, String, Arc<LockerInner>)>,
+}
+impl Drop for LockerInner {
+    fn drop(&mut self) {
+        if let Some((_, idx, parent)) = self.parent.take() {
+            Handle::current().block_on(parent.map.lock()).remove(&idx);
+        }
+    }
+}
 impl Locker {
     pub fn new() -> Self {
-        Locker(QrwLock::new(HashMap::new()))
+        Locker(Arc::new(LockerInner {
+            map: Mutex::new(HashMap::new()),
+            self_lock: Qutex::new(()),
+            children_lock: {
+                let notify = Arc::new(Notify::new());
+                notify.notify_one();
+                notify
+            },
+            guard: Mutex::new(Weak::new()),
+            parent: None,
+        }))
     }
-    fn lock_root_read<'a>(guard: &'a ReadGuard<HashMap<String, Locker>>) -> BoxFuture<'a, ()> {
-        async move {
-            for (_, v) in &**guard {
-                let g = v.0.clone().read().await.unwrap();
-                Self::lock_root_read(&g).await;
-            }
+    async fn notify_guard(&self) -> Arc<NotifyGuard> {
+        let mut lock = self.0.guard.lock().await;
+        if let Some(n) = lock.upgrade() {
+            Arc::new(NotifyGuard(n.0.clone()))
+        } else {
+            let res = Arc::new(NotifyGuard(self.0.children_lock.clone()));
+            *lock = Arc::downgrade(&res);
+            res
         }
-        .boxed()
     }
-    pub async fn lock_read<S: AsRef<str>, V: SegList>(
+    async fn child<'a, S: Into<Cow<'a, str>>>(&self, name: S) -> Locker {
+        let name: Cow<'a, str> = name.into();
+        let mut lock = self.0.map.lock().await;
+        if let Some(child) = lock.get(name.as_ref()).and_then(|w| w.upgrade()) {
+            Locker(child)
+        } else {
+            let name = name.into_owned();
+            let res = Arc::new(LockerInner {
+                map: Mutex::new(HashMap::new()),
+                self_lock: Qutex::new(()),
+                children_lock: {
+                    let notify = Arc::new(Notify::new());
+                    notify.notify_one();
+                    notify
+                },
+                guard: Mutex::new(Weak::new()),
+                parent: Some((self.notify_guard().await, name.clone(), self.0.clone())),
+            });
+            lock.insert(name, Arc::downgrade(&res));
+            Locker(res)
+        }
+    }
+    /// await once: in the queue, await twice: all children dropped
+    async fn wait_for_children<'a>(&'a self) -> BoxFuture<'a, ()> {
+        let children = self.0.guard.lock().await;
+        let mut fut = if children.strong_count() == 0 {
+            futures::future::ready(()).boxed()
+        } else {
+            self.0.children_lock.notified().boxed()
+        };
+        if matches!(futures::poll!(&mut fut), Poll::Ready(_)) {
+            return futures::future::ready(()).boxed();
+        }
+        drop(children);
+        fut
+    }
+    async fn acquire_and_trade(self, guards: Vec<LockerGuard>) -> LockerGuard {
+        let children_dropped = self.wait_for_children().await;
+        guards.into_iter().for_each(drop);
+        children_dropped.await;
+        let guard = self.0.self_lock.clone().lock().await.unwrap();
+        LockerGuard(self.notify_guard().await, guard, self.0.clone())
+    }
+    pub async fn lock<S: AsRef<str>, V: SegList>(
         &self,
         ptr: &JsonPointer<S, V>,
-        deep: bool,
-    ) -> ReadGuard<HashMap<String, Locker>> {
-        #[cfg(feature = "log")]
-        log::debug!("Locking {} for READ: {{ deep: {} }}", ptr, deep);
-        let mut lock = Some(self.0.clone().read().await.unwrap());
+        guards: Vec<LockerGuard>,
+    ) -> LockerGuard {
+        let mut locker = Locker(self.0.clone());
         for seg in ptr.iter() {
-            let new_lock = if let Some(locker) = lock.as_ref().unwrap().get(seg) {
-                locker.0.clone().read().await.unwrap()
-            } else {
-                let mut writer = ReadGuard::upgrade(lock.take().unwrap()).await.unwrap();
-                writer.insert(seg.to_owned(), Locker::new());
-                let reader = WriteGuard::downgrade(writer);
-                reader.get(seg).unwrap().0.clone().read().await.unwrap()
-            };
-            lock = Some(new_lock);
+            locker = locker.child(seg).await;
         }
-        let res = lock.unwrap();
-        if deep {
-            Self::lock_root_read(&res);
+        let res = locker.acquire_and_trade(guards).await;
+        let mut guards = Vec::with_capacity(ptr.len());
+        let mut cur = res.2.parent.as_ref().map(|(_, _, p)| p);
+        while let Some(parent) = cur {
+            guards.push(parent.self_lock.clone().lock().await.unwrap());
+            cur = parent.parent.as_ref().map(|(_, _, p)| p);
         }
-        #[cfg(feature = "log")]
-        log::debug!("Locked {} for READ: {{ deep: {} }}", ptr, deep);
         res
     }
-    pub(crate) async fn add_read_lock<S: AsRef<str> + Clone, V: SegList + Clone>(
+    /// TODO: DRAGONS!!!
+    /// Acquiring a lock to a node above something you already held will do so at the transaction level of the lock you already held!
+    /// This means even though you dropped the sub tx in which you acquired the higher level lock,
+    /// the higher lock could still be held by the parent tx which originally held the lower lock.
+    pub async fn add_lock(
         &self,
-        ptr: &JsonPointer<S, V>,
-        locks: &mut Vec<(JsonPointer, LockerGuard)>,
-        extra_locks: &mut [&mut [(JsonPointer, LockerGuard)]],
-        deep: bool,
+        ptr: &JsonPointer,
+        locks: &mut Vec<(JsonPointer, Option<LockerGuard>)>, // tx locks
+        extra_locks: &mut [&mut [(JsonPointer, Option<LockerGuard>)]], // tx parent locks
     ) {
-        for lock in extra_locks
-            .iter()
-            .flat_map(|a| a.iter())
-            .chain(locks.iter())
-        {
-            if ptr.starts_with(&lock.0) {
-                return;
-            }
-        }
-        locks.push((
-            JsonPointer::to_owned(ptr.clone()),
-            LockerGuard::Read(self.lock_read(ptr, deep).await.into()),
-        ));
-    }
-    fn lock_root_write<'a>(guard: &'a WriteGuard<HashMap<String, Locker>>) -> BoxFuture<'a, ()> {
-        async move {
-            for (_, v) in &**guard {
-                let g = v.0.clone().write().await.unwrap();
-                Self::lock_root_write(&g).await;
-            }
-        }
-        .boxed()
-    }
-    pub async fn lock_write<S: AsRef<str>, V: SegList>(
-        &self,
-        ptr: &JsonPointer<S, V>,
-        deep: bool,
-    ) -> WriteGuard<HashMap<String, Locker>> {
-        #[cfg(feature = "log")]
-        log::debug!("Locking {} for WRITE: {{ deep: {} }}", ptr, deep);
-        let mut lock = self.0.clone().write().await.unwrap();
-        for seg in ptr.iter() {
-            let new_lock = if let Some(locker) = lock.get(seg) {
-                locker.0.clone().write().await.unwrap()
-            } else {
-                lock.insert(seg.to_owned(), Locker::new());
-                lock.get(seg).unwrap().0.clone().write().await.unwrap()
-            };
-            lock = new_lock;
-        }
-        let res = lock;
-        if deep {
-            Self::lock_root_write(&res);
-        }
-        #[cfg(feature = "log")]
-        log::debug!("Locked {} for WRITE: {{ deep: {} }}", ptr, deep);
-        res
-    }
-    pub(crate) async fn add_write_lock<S: AsRef<str> + Clone, V: SegList + Clone>(
-        &self,
-        ptr: &JsonPointer<S, V>,
-        locks: &mut Vec<(JsonPointer, LockerGuard)>, // tx locks
-        extra_locks: &mut [&mut [(JsonPointer, LockerGuard)]], // tx parent locks
-        deep: bool,
-    ) {
-        let mut final_lock = None;
+        let mut lock_dest = None;
+        let mut guards = Vec::new();
         for lock in extra_locks
             .iter_mut()
             .flat_map(|a| a.iter_mut())
             .chain(locks.iter_mut())
         {
-            enum Choice {
-                Return,
-                Continue,
-                Break,
+            if ptr.starts_with(&lock.0) {
+                return;
             }
-            let choice: Choice;
-            if let Some(remainder) = ptr.strip_prefix(&lock.0) {
-                let guard = lock.1.take();
-                lock.1 = match guard {
-                    LockerGuard::Read(LockerReadGuard(guard)) if !remainder.is_empty() => {
-                        // read guard already exists at higher level
-                        let mut lock = guard.lock().await;
-                        if let Some(l) = lock.take() {
-                            let mut orig_lock = None;
-                            let mut lock = ReadGuard::upgrade(l).await.unwrap();
-                            for seg in remainder.iter() {
-                                let new_lock = if let Some(locker) = lock.get(seg) {
-                                    locker.0.clone().write().await.unwrap()
-                                } else {
-                                    lock.insert(seg.to_owned(), Locker::new());
-                                    lock.get(seg).unwrap().0.clone().write().await.unwrap()
-                                };
-                                if orig_lock.is_none() {
-                                    orig_lock = Some(lock);
-                                }
-                                lock = new_lock;
-                            }
-                            final_lock = Some(LockerGuard::Write(lock.into()));
-                            choice = Choice::Break;
-                            LockerGuard::Read(WriteGuard::downgrade(orig_lock.unwrap()).into())
-                        } else {
-                            drop(lock);
-                            choice = Choice::Return;
-                            LockerGuard::Read(LockerReadGuard(guard))
-                        }
-                    }
-                    LockerGuard::Read(l) => {
-                        // read exists, convert to write
-                        if let Some(upgraded) = l.upgrade().await {
-                            final_lock = Some(LockerGuard::Write(upgraded));
-                            choice = Choice::Break;
-                        } else {
-                            choice = Choice::Continue;
-                        }
-                        LockerGuard::Read(l)
-                    }
-                    LockerGuard::Write(l) => {
-                        choice = Choice::Return;
-                        LockerGuard::Write(l)
-                    } // leave it alone, already sufficiently locked
-                    LockerGuard::Empty => {
-                        unreachable!("LockerGuard found empty");
-                    }
-                };
-                match choice {
-                    Choice::Return => return,
-                    Choice::Break => break,
-                    Choice::Continue => continue,
+            if lock.0.starts_with(&ptr) {
+                if let Some(guard) = lock.1.take() {
+                    guards.push(guard);
+                    lock_dest = Some(lock);
                 }
             }
         }
-        locks.push((
-            JsonPointer::to_owned(ptr.clone()),
-            if let Some(lock) = final_lock {
-                lock
-            } else {
-                LockerGuard::Write(self.lock_write(ptr, deep).await.into())
-            },
-        ));
-    }
-}
-impl Default for Locker {
-    fn default() -> Self {
-        Locker::new()
+        let guard = self.lock(ptr, guards).await;
+        if let Some(lock) = lock_dest {
+            lock.0 = ptr.clone();
+            lock.1 = Some(guard);
+        } else {
+            locks.push((ptr.clone(), Some(guard)));
+        }
     }
 }

patch-db/src/model.rs

@@ -10,7 +10,6 @@ use json_ptr::JsonPointer;
 use serde::{Deserialize, Serialize};
 use serde_json::Value;
 
-use crate::locker::LockType;
 use crate::{DbHandle, DiffPatch, Error, Revision};
 
 #[derive(Debug)]
@@ -65,19 +64,19 @@ impl<T> Model<T>
 where
     T: Serialize + for<'de> Deserialize<'de>,
 {
-    pub async fn lock<Db: DbHandle>(&self, db: &mut Db, lock: LockType) {
-        db.lock(&self.ptr, lock, true).await
+    pub async fn lock<Db: DbHandle>(&self, db: &mut Db) {
+        db.lock(&self.ptr).await
     }
 
     pub async fn get<Db: DbHandle>(&self, db: &mut Db, lock: bool) -> Result<ModelData<T>, Error> {
         if lock {
-            self.lock(db, LockType::Read).await;
+            self.lock(db).await;
         }
         Ok(ModelData(db.get(&self.ptr).await?))
     }
 
     pub async fn get_mut<Db: DbHandle>(&self, db: &mut Db) -> Result<ModelDataMut<T>, Error> {
-        self.lock(db, LockType::Write).await;
+        self.lock(db).await;
         let original = db.get_value(&self.ptr, None).await?;
         let current = serde_json::from_value(original.clone())?;
         Ok(ModelDataMut {
@@ -105,7 +104,7 @@ where
         db: &mut Db,
         value: &T,
     ) -> Result<Option<Arc<Revision>>, Error> {
-        self.lock(db, LockType::Write).await;
+        self.lock(db).await;
         db.put(&self.ptr, value).await
     }
 }
@@ -209,8 +208,8 @@ impl<T: HasModel + Serialize + for<'de> Deserialize<'de>> HasModel for Box<T> {
 #[derive(Debug)]
 pub struct OptionModel<T: HasModel + Serialize + for<'de> Deserialize<'de>>(T::Model);
 impl<T: HasModel + Serialize + for<'de> Deserialize<'de>> OptionModel<T> {
-    pub async fn lock<Db: DbHandle>(&self, db: &mut Db, lock: LockType) {
-        db.lock(self.0.as_ref(), lock, true).await
+    pub async fn lock<Db: DbHandle>(&self, db: &mut Db) {
+        db.lock(self.0.as_ref()).await
     }
 
     pub async fn get<Db: DbHandle>(
@@ -219,7 +218,7 @@ impl<T: HasModel + Serialize + for<'de> Deserialize<'de>> OptionModel<T> {
         lock: bool,
     ) -> Result<ModelData<Option<T>>, Error> {
         if lock {
-            self.lock(db, LockType::Read).await;
+            self.lock(db).await;
         }
         Ok(ModelData(db.get(self.0.as_ref()).await?))
     }
@@ -228,7 +227,7 @@ impl<T: HasModel + Serialize + for<'de> Deserialize<'de>> OptionModel<T> {
         &self,
         db: &mut Db,
     ) -> Result<ModelDataMut<Option<T>>, Error> {
-        self.lock(db, LockType::Write).await;
+        self.lock(db).await;
         let original = db.get_value(self.0.as_ref(), None).await?;
         let current = serde_json::from_value(original.clone())?;
         Ok(ModelDataMut {
@@ -240,7 +239,7 @@ impl<T: HasModel + Serialize + for<'de> Deserialize<'de>> OptionModel<T> {
 
     pub async fn exists<Db: DbHandle>(&self, db: &mut Db, lock: bool) -> Result<bool, Error> {
         if lock {
-            db.lock(self.0.as_ref(), LockType::Read, false).await;
+            db.lock(self.0.as_ref()).await;
         }
         Ok(db.exists(&self.as_ref(), None).await?)
     }
@@ -284,7 +283,7 @@ impl<T: HasModel + Serialize + for<'de> Deserialize<'de>> OptionModel<T> {
     }
 
     pub async fn delete<Db: DbHandle>(&self, db: &mut Db) -> Result<Option<Arc<Revision>>, Error> {
-        db.lock(self.as_ref(), LockType::Write, true).await;
+        db.lock(self.as_ref()).await;
         db.put(self.as_ref(), &Value::Null).await
     }
 }
@@ -297,7 +296,7 @@ where
         db: &mut Db,
         value: &T,
     ) -> Result<Option<Arc<Revision>>, Error> {
-        db.lock(self.as_ref(), LockType::Write, true).await;
+        db.lock(self.as_ref()).await;
         db.put(self.as_ref(), value).await
     }
 }
@@ -461,7 +460,7 @@ where
         lock: bool,
     ) -> Result<IndexSet<T::Key>, Error> {
         if lock {
-            db.lock(self.as_ref(), LockType::Read, false).await;
+            db.lock(self.as_ref()).await;
         }
         let set = db.keys(self.as_ref(), None).await?;
         Ok(set
@@ -470,7 +469,7 @@ where
             .collect::<Result<_, _>>()?)
     }
     pub async fn remove<Db: DbHandle>(&self, db: &mut Db, key: &T::Key) -> Result<(), Error> {
-        db.lock(self.as_ref(), LockType::Write, false).await;
+        db.lock(self.as_ref()).await;
         db.apply(DiffPatch(Patch(vec![PatchOperation::Remove(
             RemoveOperation {
                 path: self.as_ref().clone().join_end(key.as_ref()),

patch-db/src/store.rs

@@ -209,7 +209,7 @@ impl Store {
 pub struct PatchDb {
     pub(crate) store: Arc<RwLock<Store>>,
     subscriber: Arc<Sender<Arc<Revision>>>,
-    pub(crate) locker: Locker,
+    pub(crate) locker: Arc<Locker>,
 }
 impl PatchDb {
     pub async fn open<P: AsRef<Path>>(path: P) -> Result<Self, Error> {
@@ -217,7 +217,7 @@ impl PatchDb {
 
         Ok(PatchDb {
             store: Arc::new(RwLock::new(Store::open(path).await?)),
-            locker: Locker::new(),
+            locker: Arc::new(Locker::new()),
             subscriber: Arc::new(subscriber),
         })
     }

patch-db/src/transaction.rs

@@ -12,7 +12,7 @@ use tokio::sync::{RwLock, RwLockReadGuard};
 use crate::store::Store;
 use crate::Error;
 use crate::{
-    locker::{LockType, Locker, LockerGuard},
+    locker::{Locker, LockerGuard},
     DbHandle,
 };
 use crate::{
@@ -22,7 +22,7 @@ use crate::{
 
 pub struct Transaction<Parent: DbHandle> {
     pub(crate) parent: Parent,
-    pub(crate) locks: Vec<(JsonPointer, LockerGuard)>,
+    pub(crate) locks: Vec<(JsonPointer, Option<LockerGuard>)>,
     pub(crate) updates: DiffPatch,
     pub(crate) sub: Receiver<Arc<Revision>>,
 }
@@ -94,7 +94,7 @@ impl<Parent: DbHandle + Send + Sync> DbHandle for Transaction<Parent> {
     fn subscribe(&self) -> Receiver<Arc<Revision>> {
         self.parent.subscribe()
     }
-    fn locker_and_locks(&mut self) -> (&Locker, Vec<&mut [(JsonPointer, LockerGuard)]>) {
+    fn locker_and_locks(&mut self) -> (&Locker, Vec<&mut [(JsonPointer, Option<LockerGuard>)]>) {
         let (locker, mut locks) = self.parent.locker_and_locks();
         locks.push(&mut self.locks);
         (locker, locks)
@@ -162,27 +162,9 @@ impl<Parent: DbHandle + Send + Sync> DbHandle for Transaction<Parent> {
         self.updates.append(patch);
         Ok(None)
     }
-    async fn lock<S: AsRef<str> + Clone + Send + Sync, V: SegList + Clone + Send + Sync>(
-        &mut self,
-        ptr: &JsonPointer<S, V>,
-        lock: LockType,
-        deep: bool,
-    ) {
-        match lock {
-            LockType::None => (),
-            LockType::Read => {
-                let (locker, mut locks) = self.parent.locker_and_locks();
-                locker
-                    .add_read_lock(ptr, &mut self.locks, &mut locks, deep)
-                    .await
-            }
-            LockType::Write => {
-                let (locker, mut locks) = self.parent.locker_and_locks();
-                locker
-                    .add_write_lock(ptr, &mut self.locks, &mut locks, deep)
-                    .await
-            }
-        }
+    async fn lock(&mut self, ptr: &JsonPointer) {
+        let (locker, mut locks) = self.parent.locker_and_locks();
+        locker.add_lock(ptr, &mut self.locks, &mut locks).await
     }
     async fn get<
         T: for<'de> Deserialize<'de>,