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fix: use unprotected V8 platform to prevent SIGSEGV on x86_64 Linux

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The default V8 platform uses Memory Protection Keys (pkeys) which
require all V8-using threads to be descendants of the thread that
called v8::Initialize. Tokio's spawn_blocking pool threads don't
satisfy this, causing SIGSEGV in WasmCodePointerTable during isolate
creation on x86_64 Linux.

Switch to new_unprotected_default_platform which relaxes the pkey
requirement. Also remove --single-threaded V8 flag (was degrading
performance without fixing the issue) and scope the creation mutex
to just JsRuntime::new() instead of the entire lifecycle.

See: https://github.com/denoland/deno_core/issues/952

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
This commit is contained in:
Ruben Fiszel
2026-02-08 13:35:59 +00:00
parent a6cf9656bb
commit 90d010347c
1 changed files with 15 additions and 6 deletions
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backend/windmill-runtime-nativets/src/lib.rs
+15 -6
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@@ -125,10 +125,9 @@ pub struct NativeAnnotation {
pub proxy: Option<(String, Option<(String, String)>)>,
}
/// Serializes V8 isolate creation to work around a V8 bug in
/// `WasmCodePointerTable::AllocateUninitializedEntry()` that causes SIGSEGV
/// when multiple isolates are created concurrently on x86_64 Linux.
/// See: https://github.com/denoland/deno_core/issues/952
/// Serializes V8 isolate creation as defense-in-depth against concurrent
/// creation races on x86_64 Linux. The primary fix is using the unprotected
/// V8 platform (see `setup_deno_runtime`).
static V8_ISOLATE_CREATE_LOCK: Mutex<()> = Mutex::new(());
/// Guard that terminates a running V8 isolate when dropped (e.g. on job cancellation).
@@ -171,7 +170,14 @@ pub fn setup_deno_runtime() -> anyhow::Result<()> {
println!("Unrecognized V8 flags: {:?}", unrecognized_v8_flags);
}
deno_core::JsRuntime::init_platform(None, false);
// Use an unprotected platform that doesn't enforce thread-isolated allocations
// via Memory Protection Keys (pkeys). The default platform requires all V8-using
// threads to be descendants of the thread that called v8::Initialize, but tokio's
// spawn_blocking pool threads don't satisfy this. Without this, V8 crashes with
// SIGSEGV in WasmCodePointerTable::AllocateUninitializedEntry() on x86_64 Linux.
// See: https://github.com/denoland/deno_core/issues/952
let platform = deno_core::v8::new_unprotected_default_platform(0, false).make_shared();
deno_core::JsRuntime::init_platform(Some(platform), false);
Ok(())
}
@@ -458,8 +464,11 @@ pub async fn eval_fetch_timeout(
let (memory_limit_tx, mut memory_limit_rx) = mpsc::unbounded_channel::<()>();
// Serialize isolate creation as extra safety net against concurrent V8
// isolate creation races. The main fix is the unprotected platform in
// setup_deno_runtime(), but this provides defense in depth.
let mut js_runtime = {
let _lock = V8_ISOLATE_CREATE_LOCK
let _v8_lock = V8_ISOLATE_CREATE_LOCK
.lock()
.unwrap_or_else(|e| e.into_inner());
JsRuntime::new(options)