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[Concurrency] Make initial executor construction fully thread safe. #81326

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Merged
merged 1 commit into from
May 12, 2025
Merged

[Concurrency] Make initial executor construction fully thread safe. #81326

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18 changes: 12 additions & 6 deletions stdlib/public/Concurrency/Executor.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -594,6 +594,14 @@ public func _createExecutors<F: ExecutorFactory>(factory: F.Type) {
Task._defaultExecutor = factory.defaultExecutor
}

@available(SwiftStdlib 6.2, *)
@_silgen_name("swift_createDefaultExecutors")
func _createDefaultExecutors() {
if Task._defaultExecutor == nil {
_createExecutors(factory: DefaultExecutorFactory.self)
}
}

#if !$Embedded && !SWIFT_STDLIB_TASK_TO_THREAD_MODEL_CONCURRENCY
extension MainActor {
@available(SwiftStdlib 6.2, *)
Expand All @@ -606,9 +614,8 @@ extension MainActor {
/// executor is a fatal error.
@available(SwiftStdlib 6.2, *)
public static var executor: any MainExecutor {
if _executor == nil {
_executor = DefaultExecutorFactory.mainExecutor
}
// It would be good if there was a Swift way to do this
_createDefaultExecutorsOnce()
return _executor!
}
}
Expand All @@ -625,9 +632,8 @@ extension Task where Success == Never, Failure == Never {
/// executor is a fatal error.
@available(SwiftStdlib 6.2, *)
public static var defaultExecutor: any TaskExecutor {
if _defaultExecutor == nil {
_defaultExecutor = DefaultExecutorFactory.defaultExecutor
}
// It would be good if there was a Swift way to do this
_createDefaultExecutorsOnce()
return _defaultExecutor!
}
}
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9 changes: 9 additions & 0 deletions stdlib/public/Concurrency/ExecutorBridge.cpp
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Expand Up @@ -14,6 +14,8 @@
#include <dispatch/dispatch.h>
#endif

#include "swift/Threading/Once.h"

#include "Error.h"
#include "ExecutorBridge.h"
#include "TaskPrivate.h"
Expand All @@ -28,6 +30,13 @@ void _swift_exit(int result) {
exit(result);
}

extern "C" SWIFT_CC(swift)
void swift_createDefaultExecutorsOnce() {
static swift::once_t createExecutorsOnce;

swift::once(createExecutorsOnce, swift_createDefaultExecutors);
}

#if SWIFT_STDLIB_TASK_TO_THREAD_MODEL_CONCURRENCY
extern "C" SWIFT_CC(swift)
SerialExecutorRef swift_getMainExecutor() {
Expand Down
8 changes: 7 additions & 1 deletion stdlib/public/Concurrency/ExecutorBridge.h
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Expand Up @@ -33,10 +33,16 @@ void swift_destroyDispatchEventC(void *event);
extern "C" SWIFT_CC(swift)
void swift_signalDispatchEvent(void *event);
#endif // !SWIFT_CONCURRENCY_EMBEDDED

extern "C" SWIFT_CC(swift) __attribute__((noreturn))
void swift_dispatchMain();

extern "C" SWIFT_CC(swift)
void swift_createDefaultExecutors();

extern "C" SWIFT_CC(swift)
void swift_createDefaultExecutorsOnce();

#pragma clang diagnostic pop

} // namespace swift
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3 changes: 3 additions & 0 deletions stdlib/public/Concurrency/ExecutorBridge.swift
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Expand Up @@ -132,3 +132,6 @@ internal func _dispatchAssertMainQueue()
internal func _getDispatchQueueForExecutor(
_ executor: UnownedSerialExecutor
) -> OpaquePointer?

@_silgen_name("swift_createDefaultExecutorsOnce")
func _createDefaultExecutorsOnce()