Jade Lovelace
b3fb8d9822
This is caused by pthread_cancel effectively throwing a not-specifically-identifiable C++ exception into the targeted thread, which, if it is not rethrown, terminates the process entirely. This is rather "impolite" behaviour, we would say. But thread cancellation is *always* busted, and we should simply not use it where unnecessary. It's particularly unnecessary when what we *actually* need it for is, err, interrupting a poll(2). That can in turn be achieved by simply listening to more stuff in the poll, namely, a pipe, which we send a character to when needing to stop the thread. While looking at this code, we also investigated whether any of the poll() madness is required, or was even *ever* required. Curiously we found in the XNU kernel source code that the thing about needing to listen to POLLHUP is probably *correct*, but switching it to POLLRDNORM should not have made any difference at all. We've left a FIXME to look into that further because what's written here is super janky. https://github.com/apple-oss-distributions/xnu/blob/94d3b452840153a99b38a3a9659680b2a006908e/bsd/kern/sys_generic.c#L1751-L1758 This is the crash on some Hydra machines: Thread 1 (Thread 0x7f56b77776c0 (LWP 955542) (Exiting)): 0 0x00007f56b8e9b7dc in __pthread_kill_implementation () from /nix/store/m71p7f0nymb19yn1dascklyya2i96jfw-glibc-2.39-52/lib/libc.so.6 1 0x00007f56b8e49516 in raise () from /nix/store/m71p7f0nymb19yn1dascklyya2i96jfw-glibc-2.39-52/lib/libc.so.6 2 0x00007f56b8e31935 in abort () from /nix/store/m71p7f0nymb19yn1dascklyya2i96jfw-glibc-2.39-52/lib/libc.so.6 3 0x00007f56b8e327f3 in __libc_message_impl.cold () from /nix/store/m71p7f0nymb19yn1dascklyya2i96jfw-glibc-2.39-52/lib/libc.so.6 4 0x00007f56b8e8e8e9 in __libc_fatal () from /nix/store/m71p7f0nymb19yn1dascklyya2i96jfw-glibc-2.39-52/lib/libc.so.6 5 0x00007f56b8ea23c4 in unwind_cleanup () from /nix/store/m71p7f0nymb19yn1dascklyya2i96jfw-glibc-2.39-52/lib/libc.so.6 6 0x00007f56b9d2a1b8 in nix::triggerInterrupt() [clone .cold] () from /nix/store/sahgw550p621m9dy1pd7whl9c5g1g0p7-lix-2.90.0-rc1/lib/liblixutil.so 7 0x00007f56b990ac9d in std::thread::_State_impl<std::thread::_Invoker<std::tuple<nix::MonitorFdHup::MonitorFdHup(int)::{lambda()#1}> > >::_M_run() () from /nix/store/sahgw550p621m9dy1pd7whl9c5g1g0p7-lix-2.90.0-rc1/lib/liblixstore.so 8 0x00007f56b90e86d3 in execute_native_thread_routine () from /nix/store/c6r62m84hywf4i6qq1h28f13zv38yqyp-gcc-13.3.0-lib/lib/libstdc++.so.6 9 0x00007f56b8e99a42 in start_thread () from /nix/store/m71p7f0nymb19yn1dascklyya2i96jfw-glibc-2.39-52/lib/libc.so.6 10 0x00007f56b8f1905c in clone3 () from /nix/store/m71p7f0nymb19yn1dascklyya2i96jfw-glibc-2.39-52/lib/libc.so.6 As for testing, we've started a daemon with this change and verified it deals with HUPs correctly on x86_64-linux, but I don't think we can easily test the destructor behaviour without whatever Hydra was doing that broke. Change-Id: I29c7de0425674494b6e43c075810126c3ff77363
Lix
Lix is an implementation of Nix, a powerful package management system for Linux and other Unix systems that makes package management reliable and reproducible.
Read more about us at https://lix.systems.
Installation
On Linux and macOS the easiest way to install Lix is to run the following shell command (as a user other than root):
$ curl -sSf -L https://install.lix.systems/lix | sh -s -- install
For systems that already have a Nix implementation installed, such as NixOS systems, read our install page
Building And Developing
See our Hacking guide in our manual for instruction on how to to set up a development environment and build Lix from source.
Additional Resources
License
Lix is released under the LGPL v2.1.