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global module registry: switch from Mutex to RwLock

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@acfoltzer identified this on a code walk through wasmtime with me,
and it was already noted in a comment that we could change if motivated.
This commit is contained in:
Pat Hickey
2021-05-27 16:12:09 -07:00
parent e25bf362ab
commit b6483e19d4
1 changed files with 6 additions and 9 deletions
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15
crates/wasmtime/src/module/registry.rs
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@@ -3,7 +3,7 @@
use crate::{signatures::SignatureCollection, Module}; use crate::{signatures::SignatureCollection, Module};
use std::{ use std::{
collections::BTreeMap, collections::BTreeMap,
sync::{Arc, Mutex}, sync::{Arc, RwLock},
}; };
use wasmtime_environ::{ use wasmtime_environ::{
entity::EntityRef, entity::EntityRef,
@@ -15,7 +15,7 @@ use wasmtime_jit::CompiledModule;
use wasmtime_runtime::{ModuleInfo, VMCallerCheckedAnyfunc, VMTrampoline}; use wasmtime_runtime::{ModuleInfo, VMCallerCheckedAnyfunc, VMTrampoline};
lazy_static::lazy_static! { lazy_static::lazy_static! {
static ref GLOBAL_MODULES: Mutex<GlobalModuleRegistry> = Default::default(); static ref GLOBAL_MODULES: RwLock<GlobalModuleRegistry> = Default::default();
} }
fn func_by_pc(module: &CompiledModule, pc: usize) -> Option<(DefinedFuncIndex, u32)> { fn func_by_pc(module: &CompiledModule, pc: usize) -> Option<(DefinedFuncIndex, u32)> {
@@ -88,7 +88,7 @@ impl ModuleRegistry {
); );
assert!(prev.is_none()); assert!(prev.is_none());
GLOBAL_MODULES.lock().unwrap().register(start, end, module); GLOBAL_MODULES.write().unwrap().register(start, end, module);
} }
/// Looks up a trampoline from an anyfunc. /// Looks up a trampoline from an anyfunc.
@@ -100,7 +100,7 @@ impl ModuleRegistry {
impl Drop for ModuleRegistry { impl Drop for ModuleRegistry {
fn drop(&mut self) { fn drop(&mut self) {
let mut info = GLOBAL_MODULES.lock().unwrap(); let mut info = GLOBAL_MODULES.write().unwrap();
for end in self.0.keys() { for end in self.0.keys() {
info.unregister(*end); info.unregister(*end);
} }
@@ -235,7 +235,7 @@ impl GlobalModuleRegistry {
/// Returns whether the `pc`, according to globally registered information, /// Returns whether the `pc`, according to globally registered information,
/// is a wasm trap or not. /// is a wasm trap or not.
pub(crate) fn is_wasm_pc(pc: usize) -> bool { pub(crate) fn is_wasm_pc(pc: usize) -> bool {
let modules = GLOBAL_MODULES.lock().unwrap(); let modules = GLOBAL_MODULES.read().unwrap();
match modules.module(pc) { match modules.module(pc) {
Some(entry) => match func_by_pc(&entry.module, pc) { Some(entry) => match func_by_pc(&entry.module, pc) {
@@ -259,11 +259,8 @@ impl GlobalModuleRegistry {
// Work with the global instance of `GlobalModuleRegistry`. Note that only // Work with the global instance of `GlobalModuleRegistry`. Note that only
// shared access is allowed, this isn't intended to mutate the contents. // shared access is allowed, this isn't intended to mutate the contents.
//
// (right now we use a `Mutex` but if motivated we could one day use a
// `RwLock`)
pub(crate) fn with<R>(f: impl FnOnce(&GlobalModuleRegistry) -> R) -> R { pub(crate) fn with<R>(f: impl FnOnce(&GlobalModuleRegistry) -> R) -> R {
f(&GLOBAL_MODULES.lock().unwrap()) f(&GLOBAL_MODULES.read().unwrap())
} }
/// Fetches frame information about a program counter in a backtrace. /// Fetches frame information about a program counter in a backtrace.