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SendableRegistry.foreachLiveWindow: Prevent concurrent modification (#2129)

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Copy the internal map values into an array before iterating.

In C++, change to recursive mutex as well.
This commit is contained in:
Peter Johnson
2019-11-25 21:47:06 -08:00
committed by GitHub
parent 6dcd2b0e2c
commit 70102a60b7
2 changed files with 14 additions and 3 deletions
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6
wpilibc/src/main/native/cpp/smartdashboard/SendableRegistry.cpp
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@@ -42,7 +42,7 @@ struct SendableRegistry::Impl {
}
};
wpi::mutex mutex;
wpi::recursive_mutex mutex;
wpi::UidVector<std::unique_ptr<Component>, 32> components;
wpi::DenseMap<void*, UID> componentMap;
@@ -310,7 +310,9 @@ void SendableRegistry::ForeachLiveWindow(
wpi::function_ref<void(CallbackData& data)> callback) const {
assert(dataHandle >= 0);
std::scoped_lock lock(m_impl->mutex);
for (auto&& comp : m_impl->components) {
wpi::SmallVector<Impl::Component*, 128> components;
for (auto&& comp : m_impl->components) components.emplace_back(comp.get());
for (auto comp : components) {
if (comp->sendable && comp->liveWindow) {
if (static_cast<size_t>(dataHandle) >= comp->data.size())
comp->data.resize(dataHandle + 1);

11
wpilibj/src/main/java/edu/wpi/first/wpilibj/smartdashboard/SendableRegistry.java
View File

@@ -8,7 +8,9 @@
package edu.wpi.first.wpilibj.smartdashboard;
import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.WeakHashMap;
import java.util.function.Consumer;
@@ -454,6 +456,10 @@ public class SendableRegistry {
public SendableBuilderImpl builder;
}
// As foreachLiveWindow is single threaded, cache the components it
// iterates over to avoid risk of ConcurrentModificationException
private static List<Component> foreachComponents = new ArrayList<>();
/**
* Iterates over LiveWindow-enabled objects in the registry.
* It is *not* safe to call other SendableRegistry functions from the
@@ -467,7 +473,9 @@ public class SendableRegistry {
public static synchronized void foreachLiveWindow(int dataHandle,
Consumer<CallbackData> callback) {
CallbackData cbdata = new CallbackData();
for (Component comp : components.values()) {
foreachComponents.clear();
foreachComponents.addAll(components.values());
for (Component comp : foreachComponents) {
if (comp.m_sendable == null) {
continue;
}
@@ -508,5 +516,6 @@ public class SendableRegistry {
}
}
}
foreachComponents.clear();
}
}