[wasm] Reduce number of write scopes for publishing

Publishing Wasm code often happens in a loop (in particular for
deserialization), so hold the {CodeSpaceWriteScope} outside that loop to
avoid repeated switching between writable and executable.

R=ahaas@chromium.org

Bug: v8:11974, chromium:1297999
Change-Id: Ic4bf859685e66c4ba297fed968d0df6ae7d24cba
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3468896Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79135}

src/wasm/code-space-access.h

@@ -53,6 +53,8 @@ class V8_NODISCARD CodeSpaceWriteScope final {
   CodeSpaceWriteScope(const CodeSpaceWriteScope&) = delete;
   CodeSpaceWriteScope& operator=(const CodeSpaceWriteScope&) = delete;
 
+  static bool IsInScope() { return code_space_write_nesting_level_ > 0; }
+
  private:
   static thread_local int code_space_write_nesting_level_;
 #if defined(DEBUG) && !V8_HAS_PTHREAD_JIT_WRITE_PROTECT

src/wasm/module-compiler.cc

@@ -3690,6 +3690,7 @@ void CompilationStateImpl::SchedulePublishCompilationResults(
     }
     publisher_running_ = true;
   }
+  CodeSpaceWriteScope code_space_write_scope(native_module_);
   while (true) {
     PublishCompilationResults(std::move(unpublished_code));
     unpublished_code.clear();

src/wasm/wasm-code-manager.cc

@@ -1264,14 +1264,14 @@ WasmCode* NativeModule::PublishCode(std::unique_ptr<WasmCode> code) {
 
 std::vector<WasmCode*> NativeModule::PublishCode(
     base::Vector<std::unique_ptr<WasmCode>> codes) {
+  // Publishing often happens in a loop, so the caller should hold the
+  // {CodeSpaceWriteScope} outside of such a loop.
+  DCHECK(CodeSpaceWriteScope::IsInScope());
   TRACE_EVENT1(TRACE_DISABLED_BY_DEFAULT("v8.wasm.detailed"),
                "wasm.PublishCode", "number", codes.size());
   std::vector<WasmCode*> published_code;
   published_code.reserve(codes.size());
   base::RecursiveMutexGuard lock(&allocation_mutex_);
-  // Get writable permission already here (and not inside the loop in
-  // {PatchJumpTablesLocked}), to avoid switching for each {code} individually.
-  CodeSpaceWriteScope code_space_write_scope(this);
   // The published code is put into the top-most surrounding {WasmCodeRefScope}.
   for (auto& code : codes) {
     published_code.push_back(PublishCodeLocked(std::move(code)));

src/wasm/wasm-serialization.cc

@@ -623,6 +623,7 @@ class PublishTask : public JobTask {
       : deserializer_(deserializer), from_queue_(from_queue) {}
 
   void Run(JobDelegate* delegate) override {
+    CodeSpaceWriteScope code_space_write_scope(deserializer_->native_module_);
     WasmCodeRefScope code_scope;
     do {
       auto to_publish = from_queue_->PopAll();