[Concurrency] Prevent task re-enqueues in continuation APIs #84944
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| Original file line number | Diff line number | Diff line change |
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@@ -889,8 +889,7 @@ internal func _resumeUnsafeThrowingContinuationWithError<T>( | |
| @available(SwiftStdlib 5.1, *) | ||
| @_alwaysEmitIntoClient | ||
| @unsafe | ||
| public nonisolated(nonsending) func withUnsafeContinuation<T>( | ||
| _ fn: (UnsafeContinuation<T, Never>) -> Void | ||
| ) async -> sending T { | ||
| return await Builtin.withUnsafeContinuation { | ||
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@@ -926,8 +925,7 @@ public func withUnsafeContinuation<T>( | |
| @available(SwiftStdlib 5.1, *) | ||
| @_alwaysEmitIntoClient | ||
| @unsafe | ||
| public nonisolated(nonsending) func withUnsafeThrowingContinuation<T>( | ||
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Contributor
Author
There was a problem hiding this comment. I hope we can get away with this "technically" source break... Let's see what the source compat suite says.
Contributor
There was a problem hiding this comment. @ktoso in practice why is the behavior different after this change? since these functions already had explicit isolated parameters that should have inherited the actor context, why would moving to implicits one cause things to function differently? |
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| _ fn: (UnsafeContinuation<T, Error>) -> Void | ||
| ) async throws -> sending T { | ||
| return try await Builtin.withUnsafeThrowingContinuation { | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,160 @@ | ||
| // RUN: %target-run-simple-swift( -target %target-swift-5.1-abi-triple %import-libdispatch) | %FileCheck %s | ||
| // RUN: %target-run-simple-swift( -O -target %target-swift-5.1-abi-triple %import-libdispatch) | %FileCheck %s | ||
| // REQUIRES: concurrency | ||
| // REQUIRES: executable_test | ||
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| // REQUIRES: concurrency_runtime | ||
| // UNSUPPORTED: back_deployment_runtime | ||
| // UNSUPPORTED: freestanding | ||
| // REQUIRES: libdispatch | ||
| // REQUIRES: synchronization | ||
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| import Synchronization | ||
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| if #available(SwiftStdlib 6.0, *) { | ||
| print("=== foo() async") | ||
| print("---------------------------------------") | ||
| await foo() | ||
| } | ||
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| // CHECK: === foo() async | ||
| // CHECK-NEXT: --------------------------------------- | ||
| // We hop to the task executor: | ||
| // CHECK-NEXT: [executor][task-executor] Enqueue (1) | ||
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| // CHECK-NEXT: foo - withTaskExecutorPreference | ||
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| // CHECK: foo - withTaskExecutorPreference - withCheckedContinuation | ||
| // CHECK-NEXT: foo - withTaskExecutorPreference - withCheckedContinuation done | ||
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| // CHECK: foo - withTaskExecutorPreference - withUnsafeContinuation | ||
| // CHECK-NEXT: foo - withTaskExecutorPreference - withUnsafeContinuation done | ||
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| // CHECK: foo - withTaskExecutorPreference - withCheckedThrowingContinuation | ||
| // CHECK-NEXT: foo - withTaskExecutorPreference - withCheckedThrowingContinuation done | ||
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| // CHECK: foo - withTaskExecutorPreference - withUnsafeThrowingContinuation | ||
| // CHECK-NEXT: foo - withTaskExecutorPreference - withUnsafeThrowingContinuation done | ||
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| // By checking that this is the second enqueue here, | ||
| // we check that there was no stray enqueues between with... invocations: | ||
| // CHECK-NEXT: [executor][task-executor] Enqueue (2) | ||
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| // CHECK-NEXT: foo - withTaskExecutorPreference done | ||
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| // CHECK-NEXT: == Make: actor Foo | ||
| // CHECK-NEXT: --------------------------------------- | ||
| // CHECK-NEXT: [executor][actor-executor] Enqueue (1) | ||
| // CHECK-NEXT: actor.foo | ||
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| // CHECK: actor.foo - withCheckedContinuation | ||
| // CHECK-NEXT: actor.foo - withCheckedContinuation done | ||
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| // CHECK: actor.foo - withUnsafeContinuation | ||
| // CHECK-NEXT: actor.foo - withUnsafeContinuation done | ||
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| // CHECK: actor.foo - withCheckedThrowingContinuation | ||
| // CHECK-NEXT: actor.foo - withCheckedThrowingContinuation done | ||
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| // CHECK: actor.foo - withUnsafeThrowingContinuation | ||
| // CHECK-NEXT: actor.foo - withUnsafeThrowingContinuation done | ||
| // CHECK-NEXT: actor.foo done | ||
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| // No more enqueues are expected afterwards | ||
| // CHECK-NOT: [executor] | ||
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| @available(SwiftStdlib 6.0, *) | ||
| @concurrent | ||
| func foo() async { | ||
| await withTaskExecutorPreference(EnqueueCountExecutor(name: "task-executor")) { | ||
| print("foo - withTaskExecutorPreference") | ||
| await withCheckedContinuation { cont in | ||
| print("foo - withTaskExecutorPreference - withCheckedContinuation") | ||
| cont.resume() | ||
| } | ||
| print("foo - withTaskExecutorPreference - withCheckedContinuation done") | ||
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| await withUnsafeContinuation { cont in | ||
| print("foo - withTaskExecutorPreference - withUnsafeContinuation") | ||
| cont.resume() | ||
| } | ||
| print("foo - withTaskExecutorPreference - withUnsafeContinuation done") | ||
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| try! await withCheckedThrowingContinuation { cont in | ||
| print("foo - withTaskExecutorPreference - withCheckedThrowingContinuation") | ||
| cont.resume() | ||
| } | ||
| print("foo - withTaskExecutorPreference - withCheckedThrowingContinuation done") | ||
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| try! await withUnsafeThrowingContinuation { cont in | ||
| print("foo - withTaskExecutorPreference - withUnsafeThrowingContinuation") | ||
| cont.resume() | ||
| } | ||
| print("foo - withTaskExecutorPreference - withUnsafeThrowingContinuation done") | ||
| } | ||
| print("foo - withTaskExecutorPreference done") | ||
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| print("== Make: actor Foo") | ||
| print("---------------------------------------") | ||
| await Foo().foo() | ||
| } | ||
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| @available(SwiftStdlib 6.0, *) | ||
| actor Foo { | ||
| let exec = EnqueueCountExecutor(name: "actor-executor") | ||
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| nonisolated var unownedExecutor: UnownedSerialExecutor { | ||
| self.exec.asUnownedSerialExecutor() | ||
| } | ||
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| func foo() async { | ||
| print("actor.foo") | ||
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| await withCheckedContinuation { cont in | ||
| print("actor.foo - withCheckedContinuation") | ||
| cont.resume() | ||
| } | ||
| print("actor.foo - withCheckedContinuation done") | ||
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| await withUnsafeContinuation { cont in | ||
| print("actor.foo - withUnsafeContinuation") | ||
| cont.resume() | ||
| } | ||
| print("actor.foo - withUnsafeContinuation done") | ||
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| try! await withCheckedThrowingContinuation { cont in | ||
| print("actor.foo - withCheckedThrowingContinuation") | ||
| cont.resume() | ||
| } | ||
| print("actor.foo - withCheckedThrowingContinuation done") | ||
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| try! await withUnsafeThrowingContinuation { cont in | ||
| print("actor.foo - withUnsafeThrowingContinuation") | ||
| cont.resume() | ||
| } | ||
| print("actor.foo - withUnsafeThrowingContinuation done") | ||
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| print("actor.foo done") | ||
| } | ||
| } | ||
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| @available(SwiftStdlib 6.0, *) | ||
| final class EnqueueCountExecutor: TaskExecutor, SerialExecutor { | ||
| let enqueueCount: Atomic<Int> | ||
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| let name: String | ||
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| init(name: String) { | ||
| self.enqueueCount = .init(0) | ||
| self.name = name | ||
| } | ||
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| public func enqueue(_ job: consuming ExecutorJob) { | ||
| let newEnqueueValue = self.enqueueCount.add(1, ordering: .relaxed).newValue | ||
| print("[executor][\(self.name)] Enqueue (\(newEnqueueValue))") | ||
| job.runSynchronously(on: self.asUnownedSerialExecutor()) | ||
| } | ||
| } | ||
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| print("done") // CHECK: done |
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'the implicit' what? (here and below)