[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
This commit is contained in:
Alex Langford 2021-08-31 11:44:34 -07:00
parent b04b757a8e
commit 862a311301
1 changed files with 15 additions and 4 deletions

View File

@ -108,10 +108,21 @@ void Language::ForEach(std::function<bool(Language *)> callback) {
}
});
// callback may call a method in Language that attempts to acquire the same
// lock (such as Language::ForEach or Language::FindPlugin). To avoid a
// deadlock, we do not use callback while holding the lock.
std::vector<Language *> loaded_plugins;
{
std::lock_guard<std::mutex> guard(GetLanguagesMutex());
LanguagesMap &map(GetLanguagesMap());
for (const auto &entry : map) {
if (!callback(entry.second.get()))
if (entry.second)
loaded_plugins.push_back(entry.second.get());
}
}
for (auto *lang : loaded_plugins) {
if (!callback(lang))
break;
}
}