digitalmars.D.bugs - [Issue 13173] New: Store reordering in core.thread / volatile fence
- via Digitalmars-d-bugs (26/26) Jul 20 2014 https://issues.dlang.org/show_bug.cgi?id=13173
https://issues.dlang.org/show_bug.cgi?id=13173 Issue ID: 13173 Summary: Store reordering in core.thread / volatile fence Product: D Version: D2 Hardware: x86 OS: Linux Status: NEW Severity: normal Priority: P1 Component: DMD Assignee: nobody puremagic.com Reporter: code klickverbot.at core.thread currently uses atomicStore!(MemoryOrder.raw) as a combined volatile store and barrier for other stores: https://github.com/D-Programming-Language/druntime/blob/3626a88e1dee58a88969f6bbfc5a1b1c74d0dee5/src/core/thread.d#L4599-L4612. This only incidentally works with DMD, as atomicStore can not be inlined there. Neither atomicStore (with any ordering) nor the proposed volatileStore can be used to fix that code, as they only affect ordering with regard to other atomic or volatile operations, and not the other plain assignments. atomicFence() would work to fix the problem, but would be much too heavy-handed, as we don't need any thread synchronization at all, just asynchronous signal safety. We really need something like C++'s std::atomic_signal_fence in druntime. DMD can just ignore it, if its optimizer doesn't reorder loads/stores anyway. --
Jul 20 2014