On Mon, May 11, 2020 at 11:38:28AM +0200, Kamil Rytarowski wrote: > On 11.05.2020 01:49, Joerg Sonnenberger wrote: > > On Mon, May 11, 2020 at 01:11:32AM +0200, Kamil Rytarowski wrote: > >> On 10.05.2020 18:38, Kamil Rytarowski wrote: > >>> LLDB will be patched to avoid atomics. > >> I have checked LLDB and std::atomic<uint64_t> is used on purpose and was > >> switched from mutexes 3 years ago. > >> > >> https://github.com/llvm/llvm-project/commit/f9d16476573e16856bdb3250c817b0a2c631d2b1 > >> > >> Reverting this (or rewriting) is not viable as this change improved the > >> performance, the code was changed meanwhile and there were added two > >> more associated std::atomic<> variables. LLDB also requires recent C++ > >> runtime. > > > > Using 64bit atomics when they are present is fine. When are not > > available, it is a huge hidden cost. This problem was discussed on the > > LLDB mailing lists a while ago and there are essentially four possible > > approaches: > > > > (1) If there are no 64bit atomic ops, go back to using the explicit > > mutex. This makes the cost explicit at the very least. > > We agreed that the primary solution is to fallback to mutexes. This is > what is done by libatomic.
Who is we again this time? I certainly didn't agree to it. Joerg
