Hi Jens, Indeed, KJ uses SIGUSR1 to communicate between threads. It sounds very obnoxious that your debugger insists on breaking on this signal. The signal is not a problem, it's a normal part of KJ's operation. With that said, you could try compiling with `-DKJ_USE_PIPE_FOR_WAKEUP`, which causes it to avoid using signals for this. You need to compile both KJ itself and your own code that depends on it with this define; if they don't match you may get undefined behavior.
`kj::newTwoWayPipe()` (the global function) is a completely in-memory implementation of TwoWayPipe which is tied to a single thread. If you use `kj::AsyncIoProvider::newTwoWayPipe()` instead, it will create an implementation backed by a socketpair(). However, unfortunately, the KJ AsyncIoStream wrapper objects are still tied to the particular thread that created them. In order to communicate between threads, you will need to manually create a socketpair(), and then use kj::LowLevelAsyncIoProvider::wrapSocketFd() to create the AsyncIoStream wrappers. Each thread would need to use its own LowLevelAsyncIoProvider object to create the AsyncIoStream for its end of the pipe. Sorry, there isn't currently a more-convenient way to do this. -Kenton On Tue, Aug 30, 2022 at 7:38 PM Jens Alfke <j...@mooseyard.com> wrote: > TL;DR: Can the two streams created by kj::newTwoWayPipe() be used on > different threads? It kind of appears not. > > I’ve found a workaround, the LLDB command > process handle --stop false SIGUSR1 > Unfortunately adding it to my .lldbrc file does nothing; I have to enter > it by hand every time I start the process. > > The next roadblock is that my unit tests create a client and a server > object, then connect them together by calling kj::newTwoWayPipe() and > giving one end of the pipe to each. This worked fine in a single thread. > However, now one end (an AsyncIoStream) gets passed into the new background > thread where the client object lives. I get an exception > "expected threadLocalEventLoop == &loop || threadLocalEventLoop == > nullptr; Event armed from different thread than it was created in. You > must use Executor to queue events cross-thread.” > > From this and the backtrace it looks as though when I write to this end of > the pipe, it wants to directly notify the other end, which won’t work > because it’s the wrong thread for that. I was hoping that the streams would > use normal Unix I/O, since the comment about the TwoWayPipe class says > "Typically backed by socketpair() system call”. > > So how do I set up streams to do I/O between threads? > > —Jens > > -- > You received this message because you are subscribed to the Google Groups > "Cap'n Proto" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to capnproto+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/capnproto/EA5DCF15-8128-4F65-AE98-708AE1B75D1E%40mooseyard.com > . > -- You received this message because you are subscribed to the Google Groups "Cap'n Proto" group. To unsubscribe from this group and stop receiving emails from it, send an email to capnproto+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/capnproto/CAJouXQnRhZViMA7rYbqZP94iw_EV-szgSLafZSnsZu6%3DKZEsxA%40mail.gmail.com.
