BillyONeal added inline comments.
================ Comment at: test/std/thread/thread.threads/thread.thread.class/thread.thread.member/detach.pass.cpp:73 assert(!t0.joinable()); while (!done) {} assert(G::op_run); ---------------- BillyONeal wrote: > dvyukov wrote: > > I don't immediately see how the race on n_alive/op_run happens. It seems > > that the modifications in the thread happen before this line, and > > modifications in main happen after this line. How can both of them modify > > the variables at the same time? > The destruction of g here races with the destruction of the DECAY_COPY'd copy > of G used as the parameter of operator(). That is, line 69 creates a copy of > g, passes that to the started thread, the started thread calls gCopy(). > gCopy() doesn't return until the done flag is set, but the destruction of the > object on which op() is being called is not so synchronized. Most of the > other thread tests avoid this problem by joining with the thread; joining > waits for the destruction of the DECAY_COPY'd parameters, but this does not. > > (This is one of the reasons detach() should basically never be called > anywhere) > (That is to say, there's nothing to prevent both threads from executing G::!G() on the two different copies of g... making op_run atomic is probably avoidable but I'm being paranoid given that there was already thread unsafety here...) https://reviews.llvm.org/D50549 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits