Add fallback implementation for waitable atomics #6293
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| { | ||
| // Initialize node from a dummy container (there is no separate node constructor) | ||
| std::multimap<const void*, waiter> dummy; | ||
| return dummy.extract(dummy.emplace(nullptr, &s_tls_waiter)); |
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May be a long shot, but won't constructing via an initializer list work? Or would that be relying on an implementation detail?
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There is no usable autonomous constructors for nodes in standard (except default and move).
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| auto& wmap = get_fallback_map(data); | ||
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| std::lock_guard lock(wmap.mutex); |
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Is shared_mutex (essentially a read/write lock) available on this platform? It'd allow concurrent access on wmap.list for reading.
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It may be available on all C++17 compatible platforms, but it's not usable with std::condition_variable, and the map is modified upon notification.
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std::condition_variable_any may meet the requirements for that.
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Oh, you can see that its implementation typically has a pair of std::mutex and std::condition_variable (which are only optimized to be interoperable).
May improve perf on OSX/BSD
May improve perf on OSX/BSD