I've seen at least two occurrences of a non-deterministic test failure in qemu for x86_64 on hydra. Both are essentially the same, except for the random seed. Here's the relevant log tail of the most recent one:
--8<---------------cut here---------------start------------->8--- GTESTER check-qtest-arm socket_accept failed: Resource temporarily unavailable ** ERROR:tests/libqtest.c:192:qtest_init: assertion failed: (s->fd >= 0 && s->qmp_fd >= 0) GTester: last random seed: R02S68ad7b4ad35e64a4283ad867738ae469 /tmp/nix-build-qemu-2.3.0.drv-0/qemu-2.3.0/tests/Makefile:416: recipe for target 'check-qtest-aarch64' failed make: *** [check-qtest-aarch64] Error 1 make: *** Waiting for unfinished jobs.... phase `check' failed after 117 seconds builder for `/gnu/store/fv3kfpi3j7vg692ibkfaw6rvid1yabvj-qemu-2.3.0.drv' failed with exit code 1 @ build-failed /gnu/store/fv3kfpi3j7vg692ibkfaw6rvid1yabvj-qemu-2.3.0.drv - 1 builder for `/gnu/store/fv3kfpi3j7vg692ibkfaw6rvid1yabvj-qemu-2.3.0.drv' failed with exit code 1 guix build: error: build failed: build of `/gnu/store/fv3kfpi3j7vg692ibkfaw6rvid1yabvj-qemu-2.3.0.drv' failed --8<---------------cut here---------------end--------------->8--- The excerpt above was from the first attempt of the following build: http://hydra.gnu.org/build/557468 After restarting the build, the second attempt succeeded. I saved a full log from another similar failure on 10 June 2015, but I neglected to save the other details. Here's the relevant tail: --8<---------------cut here---------------start------------->8--- GTESTER check-qtest-arm socket_accept failed: Resource temporarily unavailable ** ERROR:tests/libqtest.c:192:qtest_init: assertion failed: (s->fd >= 0 && s->qmp_fd >= 0) GTester: last random seed: R02Sf42b4c6eb1ed085e2ce450c1f51f3505 /tmp/nix-build-qemu-2.3.0.drv-1/qemu-2.3.0/tests/Makefile:416: recipe for target 'check-qtest-aarch64' failed make: *** [check-qtest-aarch64] Error 1 make: *** Waiting for unfinished jobs.... socket_accept failed: Resource temporarily unavailable ** ERROR:tests/libqtest.c:192:qtest_init: assertion failed: (s->fd >= 0 && s->qmp_fd >= 0) GTester: last random seed: R02S126fc36a13df8d61829c432073f209f0 /tmp/nix-build-qemu-2.3.0.drv-1/qemu-2.3.0/tests/Makefile:416: recipe for target 'check-qtest-arm' failed make: *** [check-qtest-arm] Error 1 phase `check' failed after 155 seconds builder for `/gnu/store/m0p5fjhy4jfqff7m720qw1ybv740a2jk-qemu-2.3.0.drv' failed with exit code 1 @ build-failed /gnu/store/m0p5fjhy4jfqff7m720qw1ybv740a2jk-qemu-2.3.0.drv - 1 builder for `/gnu/store/m0p5fjhy4jfqff7m720qw1ybv740a2jk-qemu-2.3.0.drv' failed with exit code 1 guix build: error: build failed: build of `/gnu/store/m0p5fjhy4jfqff7m720qw1ybv740a2jk-qemu-2.3.0.drv' failed --8<---------------cut here---------------end--------------->8--- Mark