forked from OSchip/llvm-project
[lldb] Tighten lock in Language::ForEach
It is easy to accidentally introduce a deadlock by having the callback passed to Language::ForEach also attempt to acquire the same lock. It is easy enough to disallow the callback from calling anything in Language directly, but it may happen through a series of other function/method calls. The solution I am proposing is to tighten the lock in Language::ForEach so that it is only held as we gather the currently loaded language plugins. We store them in a vector and then iterate through them with the callback so that the callback can't introduce a deadlock. Differential Revision: https://reviews.llvm.org/D109013
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@ -108,10 +108,21 @@ void Language::ForEach(std::function<bool(Language *)> callback) {
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}
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});
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// callback may call a method in Language that attempts to acquire the same
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// lock (such as Language::ForEach or Language::FindPlugin). To avoid a
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// deadlock, we do not use callback while holding the lock.
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std::vector<Language *> loaded_plugins;
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{
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std::lock_guard<std::mutex> guard(GetLanguagesMutex());
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LanguagesMap &map(GetLanguagesMap());
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for (const auto &entry : map) {
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if (!callback(entry.second.get()))
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if (entry.second)
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loaded_plugins.push_back(entry.second.get());
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}
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}
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for (auto *lang : loaded_plugins) {
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if (!callback(lang))
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break;
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}
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}
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