On 2020-07-17, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > Make sure you test the case of "fast concurrent readers". The last > time we did things like this, it was a disaster, because a concurrent > reader would see and return the _incomplete_ line, and the next entry > was still being generated on another CPU. > > The reader would then decide to return that incomplete line, because > it had something. > > And while in theory this could then be handled properly in user space, > in practice it wasn't. So you'd see a lot of logging tools that would > then report all those continuations as separate log events. > > Which is the whole point of LOG_CONT - for that *not* to happen. I expect this is handled correctly since the reader is not given any parts until a full line is ready, but I will put more focus on testing this to make sure. Thanks for the regression and testing tips. > So this is just a heads-up that I will not pull something that breaks > LOG_CONT because it thinks "user space can handle it". No. User space > does not handle it, and we need to handle it for the user. Understood. Petr and Sergey are also strict about this. We are making a serious effort to avoid breaking things for userspace. John Ogness _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
