Use an atomic for notificationIDForLogging

This allows us to get rid of the lock.

Author: ahoppen

Package.swift

@@ -312,6 +312,7 @@ let package = Package(
       name: "SourceKitLSP",
       dependencies: [
         "BuildServerProtocol",
+        "CAtomics",
         "LanguageServerProtocol",
         "LanguageServerProtocolJSONRPC",
         "LSPLogging",

Sources/CAtomics/include/CAtomics.h

@@ -63,4 +63,32 @@ static inline void atomic_uint8_set(AtomicUInt8 *atomic, uint8_t newValue) {
   atomic->value = newValue;
 }
 
+// MARK: AtomicInt
+
+typedef struct {
+  _Atomic(int) value;
+} AtomicUInt32;
+
+__attribute__((swift_name("AtomicUInt32.init(initialValue:)")))
+static inline AtomicUInt32 atomic_int_create(uint8_t initialValue) {
+  AtomicUInt32 atomic;
+  atomic.value = initialValue;
+  return atomic;
+}
+
+__attribute__((swift_name("getter:AtomicUInt32.value(self:)")))
+static inline uint32_t atomic_int_get(AtomicUInt32 *atomic) {
+  return atomic->value;
+}
+
+__attribute__((swift_name("setter:AtomicUInt32.value(self:_:)")))
+static inline void atomic_uint32_set(AtomicUInt32 *atomic, uint32_t newValue) {
+  atomic->value = newValue;
+}
+
+__attribute__((swift_name("AtomicUInt32.fetchAndIncrement(self:)")))
+static inline uint32_t atomic_uint32_fetch_and_increment(AtomicUInt32 *atomic) {
+  return atomic->value++;
+}
+
 #endif // SOURCEKITLSP_CATOMICS_H

Sources/SourceKitLSP/SourceKitLSPServer.swift

@@ -11,6 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 import BuildServerProtocol
+import CAtomics
 import Dispatch
 import Foundation
 import IndexStoreDB
@@ -812,19 +813,7 @@ public actor SourceKitLSPServer {
 
 // MARK: - MessageHandler
 
-private let notificationIDForLoggingLock = NSLock()
-private var notificationIDForLogging: Int = 0
-
-/// On every call, returns a new unique number that can be used to identify a notification.
-///
-/// This is needed so we can consistently refer to a notification using the `category` of the logger.
-/// Requests don't need this since they already have a unique ID in the LSP protocol.
-private func getNextNotificationIDForLogging() -> Int {
-  return notificationIDForLoggingLock.withLock {
-    notificationIDForLogging += 1
-    return notificationIDForLogging
-  }
-}
+private var notificationIDForLogging = AtomicUInt32(initialValue: 1)
 
 extension SourceKitLSPServer: MessageHandler {
   public nonisolated func handle(_ params: some NotificationType) {
@@ -835,7 +824,7 @@ extension SourceKitLSPServer: MessageHandler {
       self.cancelRequest(params)
     }
 
-    let notificationID = getNextNotificationIDForLogging()
+    let notificationID = notificationIDForLogging.fetchAndIncrement()
 
     let signposter = Logger(subsystem: subsystem, category: "notification-\(notificationID)").makeSignposter()
     let signpostID = signposter.makeSignpostID()