Allow cloning Rc<ContextState> into new contexts (denoland#693)

Required for  denoland#23305

Allowing cloning `Rc<ContextState>` into new contexts. 

During cleanup we assert that main context does not have more than one
strong count to `JsRuntimeState` but this may not be true when there are
more than one contexts that may not have been GC'ed yet. Hence,
JsRuntimeState is now stored as a pointer to OpCtx as it is guarnateed
to live longer than ops.

core/extension_set.rs

@@ -129,6 +129,7 @@ pub fn create_op_ctxs(
   let op_count = op_decls.len();
   let mut op_ctxs = Vec::with_capacity(op_count);
 
+  let runtime_state_ptr = runtime_state.as_ref() as *const _;
   for (index, decl) in op_decls.into_iter().enumerate() {
     let metrics_fn = op_metrics_factory_fn
       .as_ref()
@@ -140,7 +141,7 @@ pub fn create_op_ctxs(
       op_driver.clone(),
       decl,
       op_state.clone(),
-      runtime_state.clone(),
+      runtime_state_ptr,
       get_error_class_fn,
       metrics_fn,
     );

core/lib.rs

@@ -136,6 +136,7 @@ pub use crate::ops_metrics::OpMetricsSummaryTracker;
 pub use crate::path::strip_unc_prefix;
 pub use crate::runtime::stats;
 pub use crate::runtime::CompiledWasmModuleStore;
+pub use crate::runtime::ContextState;
 pub use crate::runtime::CreateRealmOptions;
 pub use crate::runtime::CrossIsolateStore;
 pub use crate::runtime::JsRuntime;

core/ops.rs

@@ -96,7 +96,7 @@ pub struct OpCtx {
   pub(crate) last_fast_error: UnsafeCell<Option<AnyError>>,
 
   op_driver: Rc<OpDriverImpl>,
-  runtime_state: Rc<JsRuntimeState>,
+  runtime_state: *const JsRuntimeState,
 }
 
 impl OpCtx {
@@ -107,7 +107,7 @@ impl OpCtx {
     op_driver: Rc<OpDriverImpl>,
     decl: OpDecl,
     state: Rc<RefCell<OpState>>,
-    runtime_state: Rc<JsRuntimeState>,
+    runtime_state: *const JsRuntimeState,
     get_error_class_fn: GetErrorClassFn,
     metrics_fn: Option<OpMetricsFn>,
   ) -> Self {
@@ -245,7 +245,8 @@ impl OpCtx {
 
   /// Get the [`JsRuntimeState`] for this op.
   pub(crate) fn runtime_state(&self) -> &JsRuntimeState {
-    &self.runtime_state
+    // SAFETY: JsRuntimeState outlives OpCtx
+    unsafe { &*self.runtime_state }
   }
 }
 

core/runtime/jsrealm.rs

@@ -49,7 +49,7 @@ impl Hasher for IdentityHasher {
 /// We may wish to experiment with alternative drivers in the future.
 pub(crate) type OpDriverImpl = super::op_driver::FuturesUnorderedDriver;
 
-pub(crate) struct ContextState {
+pub struct ContextState {
   pub(crate) task_spawner_factory: Arc<V8TaskSpawnerFactory>,
   pub(crate) timers: WebTimers<(v8::Global<v8::Function>, u32)>,
   pub(crate) js_event_loop_tick_cb:

core/runtime/mod.rs

@@ -18,7 +18,7 @@ mod tests;
 pub const V8_WRAPPER_TYPE_INDEX: i32 = 0;
 pub const V8_WRAPPER_OBJECT_INDEX: i32 = 1;
 
-pub(crate) use jsrealm::ContextState;
+pub use jsrealm::ContextState;
 pub(crate) use jsrealm::JsRealm;
 pub(crate) use jsrealm::OpDriverImpl;
 pub use jsruntime::CompiledWasmModuleStore;