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[Concurrency] Fix unsafe continuation validation when a continued task has been destroyed. #75274

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merged 1 commit into from
Jul 19, 2024
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[Concurrency] Fix unsafe continuation validation when a continued task has been destroyed. #75274

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30 changes: 16 additions & 14 deletions stdlib/public/Concurrency/Task.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1397,7 +1397,7 @@ enum class State : uint8_t { Uninitialized, On, Off };
static std::atomic<State> CurrentState;

static LazyMutex ActiveContinuationsLock;
static Lazy<std::unordered_set<ContinuationAsyncContext *>> ActiveContinuations;
static Lazy<std::unordered_set<AsyncTask *>> ActiveContinuations;

static bool isEnabled() {
auto state = CurrentState.load(std::memory_order_relaxed);
Expand All @@ -1410,39 +1410,39 @@ static bool isEnabled() {
return state == State::On;
}

static void init(ContinuationAsyncContext *context) {
static void init(AsyncTask *task) {
if (!isEnabled())
return;

LazyMutex::ScopedLock guard(ActiveContinuationsLock);
auto result = ActiveContinuations.get().insert(context);
auto result = ActiveContinuations.get().insert(task);
auto inserted = std::get<1>(result);
if (!inserted)
swift_Concurrency_fatalError(
0,
"Initializing continuation context %p that was already initialized.\n",
context);
"Initializing continuation for task %p that was already initialized.\n",
task);
}

static void willResume(ContinuationAsyncContext *context) {
static void willResume(AsyncTask *task) {
if (!isEnabled())
return;

LazyMutex::ScopedLock guard(ActiveContinuationsLock);
auto removed = ActiveContinuations.get().erase(context);
auto removed = ActiveContinuations.get().erase(task);
if (!removed)
swift_Concurrency_fatalError(0,
"Resuming continuation context %p that was not awaited "
"(may have already been resumed).\n",
context);
swift_Concurrency_fatalError(
0,
"Resuming continuation for task %p that is not awaited "
"(may have already been resumed).\n",
task);
}

} // namespace continuationChecking

SWIFT_CC(swift)
static AsyncTask *swift_continuation_initImpl(ContinuationAsyncContext *context,
AsyncContinuationFlags flags) {
continuationChecking::init(context);
context->Flags = ContinuationAsyncContext::FlagsType();
if (flags.canThrow()) context->Flags.setCanThrow(true);
if (flags.isExecutorSwitchForced())
Expand Down Expand Up @@ -1479,6 +1479,7 @@ static AsyncTask *swift_continuation_initImpl(ContinuationAsyncContext *context,
task->ResumeContext = context;
task->ResumeTask = context->ResumeParent;

continuationChecking::init(task);
concurrency::trace::task_continuation_init(task, context);

return task;
Expand Down Expand Up @@ -1593,8 +1594,6 @@ static void swift_continuation_awaitImpl(ContinuationAsyncContext *context) {

static void resumeTaskAfterContinuation(AsyncTask *task,
ContinuationAsyncContext *context) {
continuationChecking::willResume(context);

auto &sync = context->AwaitSynchronization;

auto status = sync.load(std::memory_order_acquire);
Expand Down Expand Up @@ -1644,13 +1643,15 @@ static void resumeTaskAfterContinuation(AsyncTask *task,

SWIFT_CC(swift)
static void swift_continuation_resumeImpl(AsyncTask *task) {
continuationChecking::willResume(task);
auto context = static_cast<ContinuationAsyncContext*>(task->ResumeContext);
concurrency::trace::task_continuation_resume(context, false);
resumeTaskAfterContinuation(task, context);
}

SWIFT_CC(swift)
static void swift_continuation_throwingResumeImpl(AsyncTask *task) {
continuationChecking::willResume(task);
auto context = static_cast<ContinuationAsyncContext*>(task->ResumeContext);
concurrency::trace::task_continuation_resume(context, false);
resumeTaskAfterContinuation(task, context);
Expand All @@ -1660,6 +1661,7 @@ static void swift_continuation_throwingResumeImpl(AsyncTask *task) {
SWIFT_CC(swift)
static void swift_continuation_throwingResumeWithErrorImpl(AsyncTask *task,
/* +1 */ SwiftError *error) {
continuationChecking::willResume(task);
auto context = static_cast<ContinuationAsyncContext*>(task->ResumeContext);
concurrency::trace::task_continuation_resume(context, true);
context->ErrorResult = error;
Expand Down