Jade Lovelace
9a8f111af2
My lix build failed today with this result: ``` lix> [----------] 3 tests from MonitorFdHup lix> [ RUN ] MonitorFdHup.works lix> [ OK ] MonitorFdHup.works (0 ms) lix> [ RUN ] MonitorFdHup.works_with_pipes lix> stderr: lix> Using configuration: seed=6402097764877502971 lix> libc++abi: terminating due to uncaught exception of type std::__1::future_error: The state of the promise has already been set. lix> 4/5 lix:check / libstore-unit-tests OK 1.10s lix> 5/5 lix:check / libexpr-unit-tests OK 1.12s lix> Summary of Failures: lix> 3/5 lix:check / libutil-unit-tests FAIL 0.93s killed by signal 6 SIGABRT lix> Ok: 4 lix> Fail: 1 lix> Full log written to /nix/var/nix/builds/nix-build-lix-2.94.0-dev-pre20250711-65ef28d.drv-0/source/build/meson-logs/testlog.txt ``` I had a response best described as "wtf". I think the cause of this problem is that there's a race condition with the test in which the loop gets gone around again a second time because it's triggered by the terminate fd (and I guess the flags remained what they were before? seems reasonable), and this is probably racing with the quit atomic being first to break out of the loop. I don't know how many hundreds of lixes I've compiled without my test failing, but this is definitely a bug. I don't think this affects actual usage as the only impact is repeat delivery of Ctrl-C which is harmless and which users do regularly. Change-Id: I60da81d4ac2e79052cd323b5171f9d8bd0aa6783
45 lines
912 B
C++
45 lines
912 B
C++
#pragma once
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///@file Observes a file descriptor for hang-up events and notifies a
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/// callback.
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#include <thread>
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#include <atomic>
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#include <poll.h>
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#include <sys/types.h>
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#include <unistd.h>
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#include "lix/libutil/error.hh"
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#include "lix/libutil/file-descriptor.hh"
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#include "lix/libutil/signals.hh"
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#include "lix/libutil/thread-name.hh"
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namespace nix {
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/**
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* Observes a file descriptor for hang-up events and notifies a callback if any show up.
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*
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* The callback will be called at most once.
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*/
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class MonitorFdHup
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{
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private:
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std::thread thread;
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/**
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* Pipe used to interrupt the poll()ing in the monitoring thread.
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*/
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Pipe terminatePipe;
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std::atomic_bool quit = false;
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std::function<void()> callback;
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void runThread(int watchFd, int terminateFd);
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public:
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MonitorFdHup(int fd, std::function<void()> callback = nix::triggerInterrupt);
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~MonitorFdHup();
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};
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}
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