Use local observers

leptos_reactive/Cargo.toml

@@ -8,16 +8,16 @@ repository = "https://github.com/leptos-rs/leptos"
 description = "Reactive system for the Leptos web framework."
 
 [dependencies]
-log = "0.4"
 slotmap = { version = "1", features = ["serde"] }
 serde = { version = "1", features = ["derive"] }
 serde-lite = { version = "0.3", optional = true }
 futures = { version = "0.3" }
 js-sys = "0.3"
+lazy_static = "1"
 miniserde = { version = "0.1", optional = true }
+parking_lot = "0.12"
 serde-wasm-bindgen = "0.4"
 serde_json = "1"
-base64 = "0.21"
 thiserror = "1"
 tokio = { version = "1", features = ["rt"], optional = true }
 tracing = "0.1"

leptos_reactive/src/context.rs

@@ -57,7 +57,7 @@ where
     let id = value.type_id();
 
     _ = with_runtime(cx.runtime, |runtime| {
-        let mut contexts = runtime.scope_contexts.borrow_mut();
+        let mut contexts = runtime.scope_contexts.write();
         let context = contexts.entry(cx.id).unwrap().or_insert_with(HashMap::new);
         context.insert(id, Box::new(value) as Box<dyn Any>);
     });
@@ -116,7 +116,7 @@ where
     let id = TypeId::of::<T>();
     with_runtime(cx.runtime, |runtime| {
         let local_value = {
-            let contexts = runtime.scope_contexts.borrow();
+            let contexts = runtime.scope_contexts.read();
             let context = contexts.get(cx.id);
             context
                 .and_then(|context| context.get(&id).and_then(|val| val.downcast_ref::<T>()))
@@ -124,16 +124,12 @@ where
         };
         match local_value {
             Some(val) => Some(val),
-            None => runtime
-                .scope_parents
-                .borrow()
-                .get(cx.id)
-                .and_then(|parent| {
-                    use_context::<T>(Scope {
-                        runtime: cx.runtime,
-                        id: *parent,
-                    })
-                }),
+            None => runtime.scope_parents.read().get(cx.id).and_then(|parent| {
+                use_context::<T>(Scope {
+                    runtime: cx.runtime,
+                    id: *parent,
+                })
+            }),
         }
     })
     .ok()

leptos_reactive/src/effect.rs

@@ -1,8 +1,8 @@
 #![forbid(unsafe_code)]
-use crate::runtime::{with_runtime, RuntimeId};
+use crate::runtime::{with_runtime, LocalObserver, RuntimeId};
 use crate::{debug_warn, Runtime, Scope, ScopeProperty};
 use cfg_if::cfg_if;
-use std::cell::RefCell;
+use parking_lot::RwLock;
 use std::fmt::Debug;
 
 /// Effects run a certain chunk of code whenever the signals they depend on change.
@@ -23,7 +23,6 @@ use std::fmt::Debug;
 /// the server, use [create_isomorphic_effect].
 /// ```
 /// # use leptos_reactive::*;
-/// # use log::*;
 /// # create_scope(create_runtime(), |cx| {
 /// let (a, set_a) = create_signal(cx, 0);
 /// let (b, set_b) = create_signal(cx, 0);
@@ -31,7 +30,7 @@ use std::fmt::Debug;
 /// // ✅ use effects to interact between reactive state and the outside world
 /// create_effect(cx, move |_| {
 ///   // immediately prints "Value: 0" and subscribes to `a`
-///   log::debug!("Value: {}", a());
+///   println!("Value: {}", a());
 /// });
 ///
 /// set_a(1);
@@ -80,7 +79,6 @@ where
 /// the server as well as the client.
 /// ```
 /// # use leptos_reactive::*;
-/// # use log::*;
 /// # create_scope(create_runtime(), |cx| {
 /// let (a, set_a) = create_signal(cx, 0);
 /// let (b, set_b) = create_signal(cx, 0);
@@ -88,7 +86,7 @@ where
 /// // ✅ use effects to interact between reactive state and the outside world
 /// create_isomorphic_effect(cx, move |_| {
 ///   // immediately prints "Value: 0" and subscribes to `a`
-///   log::debug!("Value: {}", a());
+///   println!("Value: {}", a());
 /// });
 ///
 /// set_a(1);
@@ -152,7 +150,7 @@ where
     F: Fn(Option<T>) -> T,
 {
     pub(crate) f: F,
-    pub(crate) value: RefCell<Option<T>>,
+    pub(crate) value: RwLock<Option<T>>,
     #[cfg(debug_assertions)]
     pub(crate) defined_at: &'static std::panic::Location<'static>,
 }
@@ -179,22 +177,22 @@ where
             )
         )
     )]
-    fn run(&self, id: EffectId, runtime: RuntimeId) {
-        _ = with_runtime(runtime, |runtime| {
+    fn run(&self, id: EffectId, runtime_id: RuntimeId) {
+        _ = with_runtime(runtime_id, |runtime| {
             // clear previous dependencies
             id.cleanup(runtime);
 
             // set this as the current observer
-            let prev_observer = runtime.observer.take();
-            runtime.observer.set(Some(id));
+            let prev_observer = LocalObserver::take(runtime_id);
+            LocalObserver::set(runtime_id, Some(id));
 
             // run the effect
-            let value = self.value.take();
+            let value = std::mem::take(&mut *self.value.write());
             let new_value = (self.f)(value);
-            *self.value.borrow_mut() = Some(new_value);
+            *self.value.write() = Some(new_value);
 
             // restore the previous observer
-            runtime.observer.set(prev_observer);
+            LocalObserver::set(runtime_id, prev_observer);
         })
     }
 }
@@ -203,7 +201,7 @@ impl EffectId {
     pub(crate) fn run<T>(&self, runtime_id: RuntimeId) {
         _ = with_runtime(runtime_id, |runtime| {
             let effect = {
-                let effects = runtime.effects.borrow();
+                let effects = runtime.effects.read();
                 effects.get(*self).cloned()
             };
             if let Some(effect) = effect {
@@ -226,12 +224,12 @@ impl EffectId {
         )
     )]
     pub(crate) fn cleanup(&self, runtime: &Runtime) {
-        let sources = runtime.effect_sources.borrow();
+        let sources = runtime.effect_sources.read();
         if let Some(sources) = sources.get(*self) {
-            let subs = runtime.signal_subscribers.borrow();
-            for source in sources.borrow().iter() {
+            let subs = runtime.signal_subscribers.read();
+            for source in sources.read().iter() {
                 if let Some(source) = subs.get(*source) {
-                    source.borrow_mut().remove(self);
+                    source.write().remove(self);
                 }
             }
         }

leptos_reactive/src/lib.rs

@@ -146,7 +146,7 @@ macro_rules! debug_warn {
         {
             #[cfg(debug_assertions)]
             {
-                log::warn!($($x)*)
+                tracing::warn!($($x)*)
             }
             #[cfg(not(debug_assertions))]
             { }

leptos_reactive/src/memo.rs

@@ -33,7 +33,7 @@ use std::fmt::Debug;
 /// let expensive = move || really_expensive_computation(value()); // lazy: doesn't run until called
 /// create_effect(cx, move |_| {
 ///   // 🆗 run #1: calls `really_expensive_computation` the first time
-///   log::debug!("expensive = {}", expensive());
+///   println!("expensive = {}", expensive());
 /// });
 /// create_effect(cx, move |_| {
 ///   // ❌ run #2: this calls `really_expensive_computation` a second time!
@@ -46,7 +46,7 @@ use std::fmt::Debug;
 /// let memoized = create_memo(cx, move |_| really_expensive_computation(value()));
 /// create_effect(cx, move |_| {
 ///  // 🆗 reads the current value of the memo
-///   log::debug!("memoized = {}", memoized());
+///   println!("memoized = {}", memoized());
 /// });
 /// create_effect(cx, move |_| {
 ///   // ✅ reads the current value **without re-running the calculation**
@@ -103,7 +103,7 @@ where
 /// let expensive = move || really_expensive_computation(value()); // lazy: doesn't run until called
 /// create_effect(cx, move |_| {
 ///   // 🆗 run #1: calls `really_expensive_computation` the first time
-///   log::debug!("expensive = {}", expensive());
+///   println!("expensive = {}", expensive());
 /// });
 /// create_effect(cx, move |_| {
 ///   // ❌ run #2: this calls `really_expensive_computation` a second time!
@@ -116,7 +116,7 @@ where
 /// let memoized = create_memo(cx, move |_| really_expensive_computation(value()));
 /// create_effect(cx, move |_| {
 ///  // 🆗 reads the current value of the memo
-///   log::debug!("memoized = {}", memoized());
+///   println!("memoized = {}", memoized());
 /// });
 /// create_effect(cx, move |_| {
 ///   // ✅ reads the current value **without re-running the calculation**

leptos_reactive/src/resource.rs

@@ -6,15 +6,10 @@ use crate::{
     spawn::spawn_local,
     use_context, Memo, ReadSignal, Scope, ScopeProperty, SuspenseContext, WriteSignal,
 };
+use parking_lot::RwLock;
 use std::{
-    any::Any,
-    cell::{Cell, RefCell},
-    collections::HashSet,
-    fmt::Debug,
-    future::Future,
-    marker::PhantomData,
-    pin::Pin,
-    rc::Rc,
+    any::Any, collections::HashSet, fmt::Debug, future::Future, marker::PhantomData, pin::Pin,
+    sync::Arc,
 };
 
 /// Creates [Resource](crate::Resource), which is a signal that reflects the
@@ -113,10 +108,10 @@ where
 
     let (loading, set_loading) = create_signal(cx, false);
 
-    let fetcher = Rc::new(move |s| Box::pin(fetcher(s)) as Pin<Box<dyn Future<Output = T>>>);
+    let fetcher = Arc::new(move |s| Box::pin(fetcher(s)) as Pin<Box<dyn Future<Output = T>>>);
     let source = create_memo(cx, move |_| source());
 
-    let r = Rc::new(ResourceState {
+    let r = Arc::new(ResourceState {
         scope: cx,
         value,
         set_value,
@@ -124,18 +119,18 @@ where
         set_loading,
         source,
         fetcher,
-        resolved: Rc::new(Cell::new(resolved)),
-        scheduled: Rc::new(Cell::new(false)),
+        resolved: Arc::new(RwLock::new(resolved)),
+        scheduled: Arc::new(RwLock::new(false)),
         suspense_contexts: Default::default(),
     });
 
     let id = with_runtime(cx.runtime, |runtime| {
-        runtime.create_serializable_resource(Rc::clone(&r))
+        runtime.create_serializable_resource(Arc::clone(&r))
     })
     .expect("tried to create a Resource in a Runtime that has been disposed.");
 
     create_isomorphic_effect(cx, {
-        let r = Rc::clone(&r);
+        let r = Arc::clone(&r);
         move |_| {
             load_resource(cx, id, r.clone());
         }
@@ -233,10 +228,10 @@ where
 
     let (loading, set_loading) = create_signal(cx, false);
 
-    let fetcher = Rc::new(move |s| Box::pin(fetcher(s)) as Pin<Box<dyn Future<Output = T>>>);
+    let fetcher = Arc::new(move |s| Box::pin(fetcher(s)) as Pin<Box<dyn Future<Output = T>>>);
     let source = create_memo(cx, move |_| source());
 
-    let r = Rc::new(ResourceState {
+    let r = Arc::new(ResourceState {
         scope: cx,
         value,
         set_value,
@@ -244,18 +239,18 @@ where
         set_loading,
         source,
         fetcher,
-        resolved: Rc::new(Cell::new(resolved)),
-        scheduled: Rc::new(Cell::new(false)),
+        resolved: Arc::new(RwLock::new(resolved)),
+        scheduled: Arc::new(RwLock::new(false)),
         suspense_contexts: Default::default(),
     });
 
     let id = with_runtime(cx.runtime, |runtime| {
-        runtime.create_unserializable_resource(Rc::clone(&r))
+        runtime.create_unserializable_resource(Arc::clone(&r))
     })
     .expect("tried to create a Resource in a runtime that has been disposed.");
 
     create_effect(cx, {
-        let r = Rc::clone(&r);
+        let r = Arc::clone(&r);
         // This is a local resource, so we're always going to handle it on the
         // client
         move |_| r.load(false)
@@ -274,7 +269,7 @@ where
 }
 
 #[cfg(not(feature = "hydrate"))]
-fn load_resource<S, T>(_cx: Scope, _id: ResourceId, r: Rc<ResourceState<S, T>>)
+fn load_resource<S, T>(_cx: Scope, _id: ResourceId, r: Arc<ResourceState<S, T>>)
 where
     S: PartialEq + Debug + Clone + 'static,
     T: 'static,
@@ -283,7 +278,7 @@ where
 }
 
 #[cfg(feature = "hydrate")]
-fn load_resource<S, T>(cx: Scope, id: ResourceId, r: Rc<ResourceState<S, T>>)
+fn load_resource<S, T>(cx: Scope, id: ResourceId, r: Arc<ResourceState<S, T>>)
 where
     S: PartialEq + Debug + Clone + 'static,
     T: Serializable + 'static,
@@ -291,12 +286,12 @@ where
     use wasm_bindgen::{JsCast, UnwrapThrowExt};
 
     _ = with_runtime(cx.runtime, |runtime| {
-        let mut context = runtime.shared_context.borrow_mut();
+        let mut context = runtime.shared_context.write();
         if let Some(data) = context.resolved_resources.remove(&id) {
             // The server already sent us the serialized resource value, so
             // deserialize & set it now
             context.pending_resources.remove(&id); // no longer pending
-            r.resolved.set(true);
+            *r.resolved.write() = true;
 
             let res = T::from_json(&data).expect_throw("could not deserialize Resource JSON");
 
@@ -318,7 +313,7 @@ where
                 move |res: String| {
                     let res =
                         T::from_json(&res).expect_throw("could not deserialize Resource JSON");
-                    resolved.set(true);
+                    *resolved.write() = true;
                     set_value.update(|n| *n = Some(res));
                     set_loading.update(|n| *n = false);
                 }
@@ -551,10 +546,10 @@ where
     set_loading: WriteSignal<bool>,
     source: Memo<S>,
     #[allow(clippy::type_complexity)]
-    fetcher: Rc<dyn Fn(S) -> Pin<Box<dyn Future<Output = T>>>>,
-    resolved: Rc<Cell<bool>>,
-    scheduled: Rc<Cell<bool>>,
-    suspense_contexts: Rc<RefCell<HashSet<SuspenseContext>>>,
+    fetcher: Arc<dyn Fn(S) -> Pin<Box<dyn Future<Output = T>>>>,
+    resolved: Arc<RwLock<bool>>,
+    scheduled: Arc<RwLock<bool>>,
+    suspense_contexts: Arc<RwLock<HashSet<SuspenseContext>>>,
 }
 
 impl<S, T> ResourceState<S, T>
@@ -583,7 +578,7 @@ where
 
         let increment = move |_: Option<()>| {
             if let Some(s) = &suspense_cx {
-                let mut contexts = suspense_contexts.borrow_mut();
+                let mut contexts = suspense_contexts.write();
                 if !contexts.contains(s) {
                     contexts.insert(*s);
 
@@ -607,21 +602,22 @@ where
 
     fn load(&self, refetching: bool) {
         // doesn't refetch if already refetching
-        if refetching && self.scheduled.get() {
+        let mut scheduled = self.scheduled.write();
+        if refetching && *scheduled {
             return;
         }
 
-        self.scheduled.set(false);
+        *scheduled = false;
 
         _ = self.source.try_with(|source| {
             let fut = (self.fetcher)(source.clone());
 
             // `scheduled` is true for the rest of this code only
-            self.scheduled.set(true);
+            *self.scheduled.write() = true;
             queue_microtask({
-                let scheduled = Rc::clone(&self.scheduled);
+                let scheduled = Arc::clone(&self.scheduled);
                 move || {
-                    scheduled.set(false);
+                    *scheduled.write() = false;
                 }
             });
 
@@ -630,7 +626,7 @@ where
             // increment counter everywhere it's read
             let suspense_contexts = self.suspense_contexts.clone();
 
-            for suspense_context in suspense_contexts.borrow().iter() {
+            for suspense_context in suspense_contexts.read().iter() {
                 suspense_context.increment();
             }
 
@@ -642,12 +638,12 @@ where
                 async move {
                     let res = fut.await;
 
-                    resolved.set(true);
+                    *resolved.write() = true;
 
                     set_value.update(|n| *n = Some(res));
                     set_loading.update(|n| *n = false);
 
-                    for suspense_context in suspense_contexts.borrow().iter() {
+                    for suspense_context in suspense_contexts.read().iter() {
                         suspense_context.decrement();
                     }
                 }
@@ -686,8 +682,8 @@ where
 }
 
 pub(crate) enum AnyResource {
-    Unserializable(Rc<dyn UnserializableResource>),
-    Serializable(Rc<dyn SerializableResource>),
+    Unserializable(Arc<dyn UnserializableResource + Send + Sync>),
+    Serializable(Arc<dyn SerializableResource + Send + Sync>),
 }
 
 pub(crate) trait SerializableResource {

leptos_reactive/src/runtime.rs

@@ -6,28 +6,30 @@ use crate::{
 };
 use cfg_if::cfg_if;
 use futures::stream::FuturesUnordered;
+use lazy_static::lazy_static;
+use parking_lot::RwLock;
 use slotmap::{SecondaryMap, SlotMap, SparseSecondaryMap};
 use std::{
     any::{Any, TypeId},
-    cell::{Cell, RefCell},
+    cell::RefCell,
     collections::{HashMap, HashSet},
     fmt::Debug,
     future::Future,
     marker::PhantomData,
     pin::Pin,
-    rc::Rc,
+    sync::Arc,
 };
 
 pub(crate) type PinnedFuture<T> = Pin<Box<dyn Future<Output = T>>>;
 
 cfg_if! {
     if #[cfg(any(feature = "csr", feature = "hydrate"))] {
-        thread_local! {
-            pub(crate) static RUNTIME: Runtime = Runtime::new();
+        lazy_static! {
+            pub(crate) static ref RUNTIME: Runtime = Runtime::new();
         }
     } else {
-        thread_local! {
-            pub(crate) static RUNTIMES: RefCell<SlotMap<RuntimeId, Runtime>> = Default::default();
+        lazy_static! {
+            pub(crate) static ref RUNTIMES: RwLock<SlotMap<RuntimeId, Runtime>> = Default::default();
         }
     }
 }
@@ -39,15 +41,13 @@ pub(crate) fn with_runtime<T>(id: RuntimeId, f: impl FnOnce(&Runtime) -> T) -> R
     cfg_if! {
         if #[cfg(any(feature = "csr", feature = "hydrate"))] {
             _ = id;
-            Ok(RUNTIME.with(|runtime| f(runtime)))
+            Ok(f(&RUNTIME))
         } else {
-            RUNTIMES.with(|runtimes| {
-                let runtimes = runtimes.borrow();
-                match runtimes.get(id) {
-                    None => Err(()),
-                    Some(runtime) => Ok(f(runtime))
-                }
-            })
+            let runtimes = RUNTIMES.read();
+            match runtimes.get(id) {
+                None => Err(()),
+                Some(runtime) => Ok(f(runtime))
+            }
         }
     }
 }
@@ -60,7 +60,7 @@ pub fn create_runtime() -> RuntimeId {
         if #[cfg(any(feature = "csr", feature = "hydrate"))] {
             Default::default()
         } else {
-            RUNTIMES.with(|runtimes| runtimes.borrow_mut().insert(Runtime::new()))
+            RUNTIMES.with(|runtimes| runtimes.write().insert(Runtime::new()))
         }
     }
 }
@@ -75,7 +75,7 @@ impl RuntimeId {
     pub fn dispose(self) {
         cfg_if! {
             if #[cfg(not(any(feature = "csr", feature = "hydrate")))] {
-                let runtime = RUNTIMES.with(move |runtimes| runtimes.borrow_mut().remove(self));
+                let runtime = RUNTIMES.with(move |runtimes| runtimes.write().remove(self));
                 drop(runtime);
             }
         }
@@ -83,7 +83,7 @@ impl RuntimeId {
 
     pub(crate) fn raw_scope_and_disposer(self) -> (Scope, ScopeDisposer) {
         with_runtime(self, |runtime| {
-            let id = { runtime.scopes.borrow_mut().insert(Default::default()) };
+            let id = { runtime.scopes.write().insert(Default::default()) };
             let scope = Scope { runtime: self, id };
             let disposer = ScopeDisposer(Box::new(move || scope.dispose()));
             (scope, disposer)
@@ -97,9 +97,9 @@ impl RuntimeId {
         parent: Option<Scope>,
     ) -> (T, ScopeId, ScopeDisposer) {
         with_runtime(self, |runtime| {
-            let id = { runtime.scopes.borrow_mut().insert(Default::default()) };
+            let id = { runtime.scopes.write().insert(Default::default()) };
             if let Some(parent) = parent {
-                runtime.scope_parents.borrow_mut().insert(id, parent.id);
+                runtime.scope_parents.write().insert(id, parent.id);
             }
             let scope = Scope { runtime: self, id };
             let val = f(scope);
@@ -121,10 +121,7 @@ impl RuntimeId {
         T: Any + 'static,
     {
         let id = with_runtime(self, |runtime| {
-            runtime
-                .signals
-                .borrow_mut()
-                .insert(Rc::new(RefCell::new(value)))
+            runtime.signals.write().insert(Arc::new(RwLock::new(value)))
         })
         .expect("tried to create a signal in a runtime that has been disposed");
         (
@@ -150,10 +147,7 @@ impl RuntimeId {
         T: Any + 'static,
     {
         let id = with_runtime(self, |runtime| {
-            runtime
-                .signals
-                .borrow_mut()
-                .insert(Rc::new(RefCell::new(value)))
+            runtime.signals.write().insert(Arc::new(RwLock::new(value)))
         })
         .expect("tried to create a signal in a runtime that has been disposed");
         RwSignal {
@@ -176,11 +170,11 @@ impl RuntimeId {
         with_runtime(self, |runtime| {
             let effect = Effect {
                 f,
-                value: RefCell::new(None),
+                value: RwLock::new(None),
                 #[cfg(debug_assertions)]
                 defined_at,
             };
-            let id = { runtime.effects.borrow_mut().insert(Rc::new(effect)) };
+            let id = { runtime.effects.write().insert(Arc::new(effect)) };
             id.run::<T>(self);
             id
         })
@@ -219,33 +213,63 @@ impl RuntimeId {
 
 #[derive(Default)]
 pub(crate) struct Runtime {
-    pub shared_context: RefCell<SharedContext>,
-    pub observer: Cell<Option<EffectId>>,
-    pub scopes: RefCell<SlotMap<ScopeId, RefCell<Vec<ScopeProperty>>>>,
-    pub scope_parents: RefCell<SparseSecondaryMap<ScopeId, ScopeId>>,
-    pub scope_children: RefCell<SparseSecondaryMap<ScopeId, Vec<ScopeId>>>,
+    pub shared_context: RwLock<SharedContext>,
+    pub scopes: RwLock<SlotMap<ScopeId, RwLock<Vec<ScopeProperty>>>>,
+    pub scope_parents: RwLock<SparseSecondaryMap<ScopeId, ScopeId>>,
+    pub scope_children: RwLock<SparseSecondaryMap<ScopeId, Vec<ScopeId>>>,
     #[allow(clippy::type_complexity)]
-    pub scope_contexts: RefCell<SparseSecondaryMap<ScopeId, HashMap<TypeId, Box<dyn Any>>>>,
+    pub scope_contexts: RwLock<SparseSecondaryMap<ScopeId, HashMap<TypeId, Box<dyn Any>>>>,
     #[allow(clippy::type_complexity)]
-    pub scope_cleanups: RefCell<SparseSecondaryMap<ScopeId, Vec<Box<dyn FnOnce()>>>>,
-    pub signals: RefCell<SlotMap<SignalId, Rc<RefCell<dyn Any>>>>,
-    pub signal_subscribers: RefCell<SecondaryMap<SignalId, RefCell<HashSet<EffectId>>>>,
-    pub effects: RefCell<SlotMap<EffectId, Rc<dyn AnyEffect>>>,
-    pub effect_sources: RefCell<SecondaryMap<EffectId, RefCell<HashSet<SignalId>>>>,
-    pub resources: RefCell<SlotMap<ResourceId, AnyResource>>,
+    pub scope_cleanups: RwLock<SparseSecondaryMap<ScopeId, Vec<Box<dyn FnOnce()>>>>,
+    pub signals: RwLock<SlotMap<SignalId, Arc<RwLock<dyn Any>>>>,
+    pub signal_subscribers: RwLock<SecondaryMap<SignalId, RwLock<HashSet<EffectId>>>>,
+    pub effects: RwLock<SlotMap<EffectId, Arc<dyn AnyEffect>>>,
+    pub effect_sources: RwLock<SecondaryMap<EffectId, RwLock<HashSet<SignalId>>>>,
+    pub resources: RwLock<SlotMap<ResourceId, AnyResource>>,
+}
+
+// track current observer thread-locally
+// because effects run synchronously, the current observer
+// *in this thread* will not change during the execution of an effect.
+// but if we track this across threads, it's possible for overlapping
+// executions to cause the stack to be out of order
+// so we store at most one current observer per runtime, per thread
+thread_local! {
+    static OBSERVER: RefCell<HashMap<RuntimeId, EffectId>> = Default::default();
+}
+
+pub(crate) struct LocalObserver {}
+
+impl LocalObserver {
+    pub fn take(runtime: RuntimeId) -> Option<EffectId> {
+        OBSERVER.with(|observer| observer.borrow_mut().remove(&runtime))
+    }
+
+    pub fn get(runtime: RuntimeId) -> Option<EffectId> {
+        OBSERVER.with(|observer| observer.borrow().get(&runtime).copied())
+    }
+
+    pub fn set(runtime: RuntimeId, effect: Option<EffectId>) {
+        OBSERVER.with(|observer| {
+            if let Some(value) = effect {
+                observer.borrow_mut().insert(runtime, value)
+            } else {
+                observer.borrow_mut().remove(&runtime)
+            }
+        });
+    }
 }
 
 impl Debug for Runtime {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         f.debug_struct("Runtime")
             .field("shared_context", &self.shared_context)
-            .field("observer", &self.observer)
             .field("scopes", &self.scopes)
             .field("scope_parents", &self.scope_parents)
             .field("scope_children", &self.scope_children)
             .field("signals", &self.signals)
             .field("signal_subscribers", &self.signal_subscribers)
-            .field("effects", &self.effects.borrow().len())
+            .field("effects", &self.effects.read().len())
             .field("effect_sources", &self.effect_sources)
             .finish()
     }
@@ -258,27 +282,27 @@ impl Runtime {
 
     pub(crate) fn create_unserializable_resource<S, T>(
         &self,
-        state: Rc<ResourceState<S, T>>,
+        state: Arc<ResourceState<S, T>>,
     ) -> ResourceId
     where
         S: Clone + 'static,
         T: 'static,
     {
         self.resources
-            .borrow_mut()
+            .write()
             .insert(AnyResource::Unserializable(state))
     }
 
     pub(crate) fn create_serializable_resource<S, T>(
         &self,
-        state: Rc<ResourceState<S, T>>,
+        state: Arc<ResourceState<S, T>>,
     ) -> ResourceId
     where
         S: Clone + 'static,
         T: Serializable + 'static,
     {
         self.resources
-            .borrow_mut()
+            .write()
             .insert(AnyResource::Serializable(state))
     }
 
@@ -291,7 +315,7 @@ impl Runtime {
         S: 'static,
         T: 'static,
     {
-        let resources = self.resources.borrow();
+        let resources = self.resources.read();
         let res = resources.get(id);
         if let Some(res) = res {
             let res_state = match res {
@@ -317,7 +341,7 @@ impl Runtime {
     /// Returns IDs for all [Resource]s found on any scope.
     pub(crate) fn all_resources(&self) -> Vec<ResourceId> {
         self.resources
-            .borrow()
+            .read()
             .iter()
             .map(|(resource_id, _)| resource_id)
             .collect()
@@ -326,7 +350,7 @@ impl Runtime {
     /// Returns IDs for all [Resource]s found on any scope, pending from the server.
     pub(crate) fn pending_resources(&self) -> Vec<ResourceId> {
         self.resources
-            .borrow()
+            .read()
             .iter()
             .filter_map(|(resource_id, res)| {
                 if matches!(res, AnyResource::Serializable(_)) {
@@ -342,7 +366,7 @@ impl Runtime {
         &self,
     ) -> FuturesUnordered<PinnedFuture<(ResourceId, String)>> {
         let f = FuturesUnordered::new();
-        for (id, resource) in self.resources.borrow().iter() {
+        for (id, resource) in self.resources.read().iter() {
             if let AnyResource::Serializable(resource) = resource {
                 f.push(resource.to_serialization_resolver(id));
             }

leptos_reactive/src/scope.rs

@@ -1,6 +1,6 @@
 #![forbid(unsafe_code)]
 use crate::{
-    runtime::{with_runtime, RuntimeId},
+    runtime::{with_runtime, LocalObserver, RuntimeId},
     EffectId, PinnedFuture, ResourceId, SignalId, SuspenseContext,
 };
 use futures::stream::FuturesUnordered;
@@ -108,7 +108,7 @@ impl Scope {
     pub fn run_child_scope<T>(self, f: impl FnOnce(Scope) -> T) -> (T, ScopeDisposer) {
         let (res, child_id, disposer) = self.runtime.run_scope_undisposed(f, Some(self));
         _ = with_runtime(self.runtime, |runtime| {
-            let mut children = runtime.scope_children.borrow_mut();
+            let mut children = runtime.scope_children.write();
             children
                 .entry(self.id)
                 .expect("trying to add a child to a Scope that has already been disposed")
@@ -145,9 +145,9 @@ impl Scope {
     /// ```
     pub fn untrack<T>(&self, f: impl FnOnce() -> T) -> T {
         with_runtime(self.runtime, |runtime| {
-            let prev_observer = runtime.observer.take();
+            let prev_observer = LocalObserver::take(self.runtime);
             let untracked_result = f();
-            runtime.observer.set(prev_observer);
+            LocalObserver::set(self.runtime, prev_observer);
             untracked_result
         })
         .expect("tried to run untracked function in a runtime that has been disposed")
@@ -167,7 +167,7 @@ impl Scope {
         _ = with_runtime(self.runtime, |runtime| {
             // dispose of all child scopes
             let children = {
-                let mut children = runtime.scope_children.borrow_mut();
+                let mut children = runtime.scope_children.write();
                 children.remove(self.id)
             };
 
@@ -182,7 +182,7 @@ impl Scope {
             }
 
             // run cleanups
-            if let Some(cleanups) = runtime.scope_cleanups.borrow_mut().remove(self.id) {
+            if let Some(cleanups) = runtime.scope_cleanups.write().remove(self.id) {
                 for cleanup in cleanups {
                     cleanup();
                 }
@@ -190,34 +190,34 @@ impl Scope {
 
             // remove everything we own and run cleanups
             let owned = {
-                let owned = runtime.scopes.borrow_mut().remove(self.id);
-                owned.map(|owned| owned.take())
+                let owned = runtime.scopes.write().remove(self.id);
+                owned.map(|owned| std::mem::take(&mut *owned.write()))
             };
             if let Some(owned) = owned {
                 for property in owned {
                     match property {
                         ScopeProperty::Signal(id) => {
                             // remove the signal
-                            runtime.signals.borrow_mut().remove(id);
-                            let subs = runtime.signal_subscribers.borrow_mut().remove(id);
+                            runtime.signals.write().remove(id);
+                            let subs = runtime.signal_subscribers.write().remove(id);
 
                             // each of the subs needs to remove the signal from its dependencies
                             // so that it doesn't try to read the (now disposed) signal
                             if let Some(subs) = subs {
-                                let source_map = runtime.effect_sources.borrow();
-                                for effect in subs.borrow().iter() {
+                                let source_map = runtime.effect_sources.read();
+                                for effect in subs.read().iter() {
                                     if let Some(effect_sources) = source_map.get(*effect) {
-                                        effect_sources.borrow_mut().remove(&id);
+                                        effect_sources.write().remove(&id);
                                     }
                                 }
                             }
                         }
                         ScopeProperty::Effect(id) => {
-                            runtime.effects.borrow_mut().remove(id);
-                            runtime.effect_sources.borrow_mut().remove(id);
+                            runtime.effects.write().remove(id);
+                            runtime.effect_sources.write().remove(id);
                         }
                         ScopeProperty::Resource(id) => {
-                            runtime.resources.borrow_mut().remove(id);
+                            runtime.resources.write().remove(id);
                         }
                     }
                 }
@@ -227,18 +227,18 @@ impl Scope {
 
     pub(crate) fn with_scope_property(&self, f: impl FnOnce(&mut Vec<ScopeProperty>)) {
         _ = with_runtime(self.runtime, |runtime| {
-            let scopes = runtime.scopes.borrow();
+            let scopes = runtime.scopes.read();
             let scope = scopes
                 .get(self.id)
                 .expect("tried to add property to a scope that has been disposed");
-            f(&mut scope.borrow_mut());
+            f(&mut scope.write());
         })
     }
 
     /// Returns the the parent Scope, if any.
     pub fn parent(&self) -> Option<Scope> {
         with_runtime(self.runtime, |runtime| {
-            runtime.scope_parents.borrow().get(self.id).copied()
+            runtime.scope_parents.read().get(self.id).copied()
         })
         .ok()
         .flatten()
@@ -255,7 +255,7 @@ impl Scope {
 /// are invalidated.
 pub fn on_cleanup(cx: Scope, cleanup_fn: impl FnOnce() + 'static) {
     _ = with_runtime(cx.runtime, |runtime| {
-        let mut cleanups = runtime.scope_cleanups.borrow_mut();
+        let mut cleanups = runtime.scope_cleanups.write();
         let cleanups = cleanups
             .entry(cx.id)
             .expect("trying to clean up a Scope that has already been disposed")
@@ -327,7 +327,7 @@ impl Scope {
         use futures::StreamExt;
 
         _ = with_runtime(self.runtime, |runtime| {
-            let mut shared_context = runtime.shared_context.borrow_mut();
+            let mut shared_context = runtime.shared_context.write();
             let (tx, mut rx) = futures::channel::mpsc::unbounded();
 
             create_isomorphic_effect(*self, move |_| {
@@ -355,7 +355,7 @@ impl Scope {
     /// `<Suspense/>` HTML when all resources are resolved.
     pub fn pending_fragments(&self) -> HashMap<String, (String, PinnedFuture<String>)> {
         with_runtime(self.runtime, |runtime| {
-            let mut shared_context = runtime.shared_context.borrow_mut();
+            let mut shared_context = runtime.shared_context.write();
             std::mem::take(&mut shared_context.pending_fragments)
         })
         .unwrap_or_default()

leptos_reactive/src/signal.rs

@@ -1,7 +1,7 @@
 #![forbid(unsafe_code)]
 use crate::{
     debug_warn,
-    runtime::{with_runtime, RuntimeId},
+    runtime::{with_runtime, LocalObserver, RuntimeId},
     Runtime, Scope, ScopeProperty, UntrackedGettableSignal, UntrackedSettableSignal,
 };
 use cfg_if::cfg_if;
@@ -246,7 +246,9 @@ where
 
     #[cfg(feature = "hydrate")]
     pub(crate) fn subscribe(&self) {
-        _ = with_runtime(self.runtime, |runtime| self.id.subscribe(runtime))
+        _ = with_runtime(self.runtime, |runtime| {
+            self.id.subscribe(self.runtime, runtime)
+        })
     }
 
     /// Clones and returns the current value of the signal, and subscribes
@@ -286,7 +288,9 @@ where
     /// Applies the function to the current Signal, if it exists, and subscribes
     /// the running effect.
     pub(crate) fn try_with<U>(&self, f: impl FnOnce(&T) -> U) -> Result<U, SignalError> {
-        match with_runtime(self.runtime, |runtime| self.id.try_with(runtime, f)) {
+        match with_runtime(self.runtime, |runtime| {
+            self.id.try_with(self.runtime, runtime, f)
+        }) {
             Ok(Ok(v)) => Ok(v),
             Ok(Err(e)) => Err(e),
             Err(_) => Err(SignalError::RuntimeDisposed),
@@ -1169,20 +1173,20 @@ pub(crate) enum SignalError {
 }
 
 impl SignalId {
-    pub(crate) fn subscribe(&self, runtime: &Runtime) {
+    pub(crate) fn subscribe(&self, runtime_id: RuntimeId, runtime: &Runtime) {
         // add subscriber
-        if let Some(observer) = runtime.observer.get() {
+        if let Some(observer) = LocalObserver::get(runtime_id) {
             // add this observer to the signal's dependencies (to allow notification)
-            let mut subs = runtime.signal_subscribers.borrow_mut();
+            let mut subs = runtime.signal_subscribers.write();
             if let Some(subs) = subs.entry(*self) {
-                subs.or_default().borrow_mut().insert(observer);
+                subs.or_default().write().insert(observer);
             }
 
             // add this signal to the effect's sources (to allow cleanup)
-            let mut effect_sources = runtime.effect_sources.borrow_mut();
+            let mut effect_sources = runtime.effect_sources.write();
             if let Some(effect_sources) = effect_sources.entry(observer) {
                 let sources = effect_sources.or_default();
-                sources.borrow_mut().insert(*self);
+                sources.write().insert(*self);
             }
         }
     }
@@ -1197,7 +1201,7 @@ impl SignalId {
     {
         // get the value
         let value = {
-            let signals = runtime.signals.borrow();
+            let signals = runtime.signals.read();
             match signals.get(*self).cloned().ok_or(SignalError::Disposed) {
                 Ok(s) => Ok(s),
                 Err(e) => {
@@ -1206,12 +1210,13 @@ impl SignalId {
                 }
             }
         }?;
-        let value = value.try_borrow().unwrap_or_else(|e| {
-            debug_warn!(
-                "Signal::try_with_no_subscription failed on Signal<{}>. It seems you're trying to read the value of a signal within an effect caused by updating the signal.",
+        let value = value.try_read().unwrap_or_else(|| {
+            panic!(
+                "Signal::try_with_no_subscription failed on Signal<{}>. \
+                It seems you're trying to read the value of a signal within an effect \
+                caused by updating the signal.",
                 std::any::type_name::<T>()
             );
-            panic!("{e}");
         });
         let value = value
             .downcast_ref::<T>()
@@ -1221,13 +1226,14 @@ impl SignalId {
 
     pub(crate) fn try_with<T, U>(
         &self,
+        runtime_id: RuntimeId,
         runtime: &Runtime,
         f: impl FnOnce(&T) -> U,
     ) -> Result<U, SignalError>
     where
         T: 'static,
     {
-        self.subscribe(runtime);
+        self.subscribe(runtime_id, runtime);
 
         self.try_with_no_subscription(runtime, f)
     }
@@ -1246,12 +1252,14 @@ impl SignalId {
         .expect("tried to access a signal in a runtime that has been disposed")
     }
 
-    pub(crate) fn with<T, U>(&self, runtime: RuntimeId, f: impl FnOnce(&T) -> U) -> U
+    pub(crate) fn with<T, U>(&self, runtime_id: RuntimeId, f: impl FnOnce(&T) -> U) -> U
     where
         T: 'static,
     {
-        with_runtime(runtime, |runtime| self.try_with(runtime, f).unwrap())
-            .expect("tried to access a signal in a runtime that has been disposed")
+        with_runtime(runtime_id, |runtime| {
+            self.try_with(runtime_id, runtime, f).unwrap()
+        })
+        .expect("tried to access a signal in a runtime that has been disposed")
     }
 
     fn update_value<T, U>(&self, runtime: RuntimeId, f: impl FnOnce(&mut T) -> U) -> Option<U>
@@ -1260,11 +1268,11 @@ impl SignalId {
     {
         with_runtime(runtime, |runtime| {
             let value = {
-                let signals = runtime.signals.borrow();
+                let signals = runtime.signals.read();
                 signals.get(*self).cloned()
             };
             if let Some(value) = value {
-                let mut value = value.borrow_mut();
+                let mut value = value.write();
                 if let Some(value) = value.downcast_mut::<T>() {
                     Some(f(value))
                 } else {
@@ -1300,14 +1308,14 @@ impl SignalId {
             // notify subscribers
             if updated.is_some() {
                 let subs = {
-                    let subs = runtime.signal_subscribers.borrow();
+                    let subs = runtime.signal_subscribers.read();
                     let subs = subs.get(*self);
-                    subs.map(|subs| subs.borrow().clone())
+                    subs.map(|subs| subs.read().clone())
                 };
                 if let Some(subs) = subs {
                     for sub in subs {
                         let effect = {
-                            let effects = runtime.effects.borrow();
+                            let effects = runtime.effects.read();
                             effects.get(sub).cloned()
                         };
                         if let Some(effect) = effect {

leptos_reactive/tests/untracked.rs

@@ -19,7 +19,7 @@ fn untracked_set_doesnt_trigger_effect() {
         create_isomorphic_effect(cx, {
             let b = b.clone();
             move |_| {
-                let formatted = format!("Value is {}", a());
+                let formatted = format!("Value is {}", a.get());
                 *b.borrow_mut() = formatted;
             }
         });
@@ -52,7 +52,7 @@ fn untracked_get_doesnt_trigger_effect() {
         create_isomorphic_effect(cx, {
             let b = b.clone();
             move |_| {
-                let formatted = format!("Values are {} and {}", a(), a2.get_untracked());
+                let formatted = format!("Values are {} and {}", a.get(), a2.get_untracked());
                 *b.borrow_mut() = formatted;
             }
         });