[Concurrency] DispatchSerialQueue does not exist on linux still

Author: ktoso

include/swift/ABI/Executor.h

@@ -77,7 +77,9 @@ class SerialExecutorRef {
     /// Executor that may need to participate in complex "same context" checks,
     /// by invoking `isSameExclusiveExecutionContext` when comparing execution contexts.
     ComplexEquality = 0b01,
-    ///
+    /// Mark this executor as the one used by `Task.startSynchronously`,
+    /// It cannot participate in switching.
+    // TODO: Perhaps make this a generic "cannot switch" rather than start synchronously specific.
     StartSynchronously = 0b10,
   };
 

stdlib/public/Concurrency/Actor.cpp

@@ -134,8 +134,6 @@ class ExecutorTrackingInfo {
   /// is `generic`.
   TaskExecutorRef TaskExecutor = TaskExecutorRef::undefined();
 
-  bool StartedSynchronouslySkipSwitchOnce = false;
-
   /// Whether this context allows switching.  Some contexts do not;
   /// for example, we do not allow switching from swift_job_run
   /// unless the passed-in executor is generic.
@@ -179,7 +177,7 @@ class ExecutorTrackingInfo {
   }
 
   bool allowsSwitching() const {
-    return AllowsSwitching && !StartedSynchronouslySkipSwitchOnce;
+    return AllowsSwitching;
   }
 
   /// Disallow switching in this tracking context.  This should only
@@ -188,16 +186,6 @@ class ExecutorTrackingInfo {
     AllowsSwitching = false;
   }
 
-  void markSynchronousStart() {
-    StartedSynchronouslySkipSwitchOnce = true;
-  }
-  bool isSynchronousStart() const {
-    return StartedSynchronouslySkipSwitchOnce;
-  }
-  void withoutStartSynchronously() {
-    StartedSynchronouslySkipSwitchOnce = false;
-  }
-
   static ExecutorTrackingInfo *current() {
     return ActiveInfoInThread.get();
   }
@@ -2170,10 +2158,6 @@ static bool canGiveUpThreadForSwitch(ExecutorTrackingInfo *trackingInfo,
   // We can certainly "give up" a generic executor to try to run
   // a task for an actor.
   if (currentExecutor.isGeneric()) {
-    if (trackingInfo->isSynchronousStart()) {
-      return false;
-    }
-
     if (currentExecutor.isForSynchronousStart()) {
       return false;
     }

stdlib/public/Concurrency/TaskPrivate.h

@@ -44,7 +44,7 @@ namespace swift {
 #if 0
 #define SWIFT_TASK_DEBUG_LOG_ENABLED 1
 #define SWIFT_TASK_DEBUG_LOG(fmt, ...)                                         \
-  fprintf(stdout, "[%#lx] [%s:%d](%s) " fmt "\n",                              \
+  fprintf(stderr, "[%#lx] [%s:%d](%s) " fmt "\n",                              \
           (unsigned long)Thread::current().platformThreadId(), __FILE__,       \
           __LINE__, __FUNCTION__, __VA_ARGS__)
 #else

test/Concurrency/Runtime/startSynchronously.swift

@@ -319,7 +319,7 @@ func callActorFromStartSynchronousTask(recipient rec: TargetActorToCall) {
 
 print("\n\n==== ------------------------------------------------------------------")
 print("callActorFromStartSynchronousTask() - actor in custom executor with its own queue")
-let actorQueue = DispatchSerialQueue(label: "recipient-actor-queue")
+let actorQueue = DispatchQueue(label: "recipient-actor-queue")
 callActorFromStartSynchronousTask(recipient: .recipientOnQueue(RecipientOnQueue(queue: actorQueue)))
 
 // CHECK-LABEL: callActorFromStartSynchronousTask() - actor in custom executor with its own queue
@@ -367,7 +367,7 @@ actor RecipientOnQueue {
   let executor: NaiveQueueExecutor
   nonisolated let unownedExecutor: UnownedSerialExecutor
 
-  init(queue: DispatchSerialQueue) {
+  init(queue: DispatchQueue) {
     self.executor = NaiveQueueExecutor(queue: queue)
     self.unownedExecutor = executor.asUnownedSerialExecutor()
   }