Ok, I'm not sure this is a bug in DragonFly. When I ktrace -i the test program threaded, another thread is doing a wait4(-1, ...) at the same as the thread doing wait4(specific_pid, ...). The specific pid is being repeated by the thread doing the wait4(-1, ...), so the thread doing the wait4(specific_pid, ...) doe sproperly return SIGCHLD in that situation.
-Matt On Tue, Jul 11, 2017 at 9:13 AM, Matthew Dillon <dil...@backplane.com> wrote: > I assume you meant ECHILD? That would definitely be a bug if there are > still children present after one exits. > > -Matt > > On Mon, Jul 10, 2017 at 8:29 AM, Imre Vadász <imrev...@gmail.com> wrote: > >> Ok, not related to SIGCHLD or anything like that. What I see when running >> that binary, is that 2 threads are blocking in wait() and when a child >> exit()s, one wait successfully returns. But the other one erronously >> reports SIGCHLD instead of continuing to block as would be expected. This >> definitely looks like a bug in the wait4 syscall, judging from the trace I >> got with "ktrace -i ./test-nix --test-threads 4" here. >> >> >> On Monday, July 10, 2017, Imre Vadász <imrev...@gmail.com> wrote: >> >>> Hi, >>> Did you verify that the child isn't just exiting before the parent calls >>> wait(), and getting reaped by a signal handler for SIGCHLD? This should be >>> easy to verify by running the binary with ktrace. In that case getting >>> ECHILD from waitpid() would be perfectly fine and could be treated as >>> success. >>> Regards, Imre >>> >>> On Monday, July 10, 2017, Michael Neumann <mneum...@ntecs.de> wrote: >>> >>>> >>>> >>>> On 07/10/17 15:40, Michael Neumann wrote: >>>> > Hi, >>>> > >>>> > I am trying to port some Rust libraries to DragonFly, specifically the >>>> > [nix] crate to access UN*X APIs from Rust. >>>> >>>> I think it's related to the problems that can occur when fork()ing a >>>> multi-threaded program, as described here: >>>> >>>> http://www.linuxprogrammingblog.com/threads-and-fork-think-t >>>> wice-before-using-them >>>> >>>> Furthermore, I think this is similar to the "cargo" issue I am seeing, >>>> when running multi-threaded (it is forking and execve "rustc" and >>>> probably doing something in between... sometimes it hangs). >>>> >>>> >>>> Regards, >>>> >>>> Michael >>>> >>> >
