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Strengthen the 'ReleaseEventListener()` guarantees. #1184

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11 changes: 3 additions & 8 deletions gloop/perftools/tracing/sync_context.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -170,17 +170,12 @@ SyncContext::Impl* SyncContext::Impl::RemoveListenerFromCurrent(
auto [new_listener, success] = active_listener->Extract(listener);
if (!PERFTOOLS_VERIFY(success)) return this;

// Signal end of sync session. This is the last event delivered
// where the listener is reachable through the active listener.
// Signal end of sync session and release listener.
listener->OnTraceEndSync(active_sync_id_);

// Set the new listener minus the extracted one and release the listener.
// We guarantee the removed listener can no longer be reached / invoked
// from a call the `ReleaseEventListener()`.
internal::set_active_event_listener(new_listener);
listener->ReleaseEventListener();

// Check if we have remaining listeners. If so, we are still "alive".
// Set the new listener and check if we have remaining listeners.
internal::set_active_event_listener(new_listener);
if (new_listener != nullptr) return this;

// All listeners are removed, delete ourselves.
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5 changes: 0 additions & 5 deletions gloop/perftools/tracing/sync_context.h
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Expand Up @@ -251,11 +251,6 @@ class ABSL_ATTRIBUTE_TRIVIAL_ABI SyncContext {
// This function is a no-op if `listener` is null.
// If `listener` is not present in this instance, then this function will
// check fail in debug builds, and release the listener in production builds.
// Any call to `ReleaseEventListener()` on the provided `listener` or any
// embedded (multiplexed) listeners inside `listeners` is guaranteed to
// occur _after_ the current active listener for the instance has been
// updated. I.e.: The listener is no longer invoked from traced calls from
// non trivial code executed by any listener specific release logic.
void RemoveListenerFromCurrent(Access, TraceEventListener* listener);

// Returns `true` if the provided listener is present in this instance.
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29 changes: 5 additions & 24 deletions gloop/perftools/tracing/sync_context_test.cc
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Expand Up @@ -529,34 +529,15 @@ TEST_F(SyncContextTest, RemoveListenersFromCurrent) {
EXPECT_CALL(mock1, OnTraceBeginSync(kMainSyncId, _));
EXPECT_CALL(mock2, OnTraceBeginSync(kMainSyncId, _));
WithContext with(std::move(root));
TraceEventListener* active_listener = internal::active_event_listener();

// EndSync() is the last sync event invoked.
EXPECT_CALL(mock2, OnTraceEndSync(kMainSyncId)).WillOnce([&](auto) {
EXPECT_THAT(internal::active_event_listener(), Eq(active_listener));
});
// Extract() is the final interaction where active listener is in place.
EXPECT_CALL(mock2, Extract(&mock2)).WillOnce([&](auto...) {
EXPECT_THAT(internal::active_event_listener(), Eq(active_listener));
return std::pair<TraceEventListener*, bool>(nullptr, true);
});
// Release() is guaranteed to be invoked after the active listener is reset.
EXPECT_CALL(mock2, ReleaseEventListener()).WillOnce([&](auto...) {
EXPECT_THAT(internal::active_event_listener(), Eq(&mock1));
});
EXPECT_CALL(mock2, OnTraceEndSync(kMainSyncId));
EXPECT_CALL(mock2, Extract(&mock2));
EXPECT_CALL(mock2, ReleaseEventListener());
Context::RemoveListenerFromCurrent(&mock2);

// EndSync() is the last sync event invoked.
EXPECT_CALL(mock1, OnTraceEndSync(kMainSyncId));
// Extract() is the final interaction where active listener is in place.
EXPECT_CALL(mock1, Extract(&mock1)).WillOnce([&](auto...) {
EXPECT_THAT(internal::active_event_listener(), Eq(&mock1));
return std::pair<TraceEventListener*, bool>(nullptr, true);
});
// Release() is guaranteed to be invoked after the active listener is reset.
EXPECT_CALL(mock1, ReleaseEventListener()).WillOnce([&](auto...) {
EXPECT_THAT(internal::active_event_listener(), Eq(nullptr));
});
EXPECT_CALL(mock1, Extract(&mock1));
EXPECT_CALL(mock1, ReleaseEventListener());
Context::RemoveListenerFromCurrent(&mock1);
}

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