Fixes#6122, which reports a problem with trying to run the installer
under another user (probably: user is not the disk "owner" and thus
can't mount the volume).
This also makes sure that we get the Docker images from the same Hydra
eval, rather than the latest build from job/nix/.../dockerImage, which
may not be the same.
On Nix 2.6 the output of `nix why-depends --all` seems to be somewhat
off:
$ nix why-depends /nix/store/kn47hayxab8gc01jhr98dwyywbx561aq-nixos-system-roflmayr-21.11.20220207.6c202a9.drv /nix/store/srn5jbs1q30jpybdmxqrwskyny659qgc-nix-2.6.drv --derivation --extra-experimental-features nix-command --all
/nix/store/kn47hayxab8gc01jhr98dwyywbx561aq-nixos-system-roflmayr-21.11.20220207.6c202a9.drv
└───/nix/store/g8bpgfjhh5vxrdq0w6r6s64f9kkm9z6c-etc.drv
│ └───/nix/store/hm0jmhp8shbf3cl846a685nv4f5cp3fy-nspawn-inst.drv
| [...]
└───/nix/store/2d6q3ygiim9ijl5d4h0qqx6vnjgxywyr-system-units.drv
└───/nix/store/dil014y1b8qyjhhhf5fpaah5fzdf0bzs-unit-systemd-nspawn-hydra.service.drv
└───/nix/store/a9r72wwx8qrxyp7hjydyg0gsrwnn26zb-activate.drv
└───/nix/store/99hlc7i4gl77wq087lbhag4hkf3kvssj-nixos-system-hydra-21.11pre-git.drv
Please note that `[...]-system-units.drv` is supposed to be a direct
child of `[...]-etc.drv`.
The reason for that is that each new level printed by `printNode` is
four spaces off in comparison to `nix why-depends --precise` because the
recursive `printNode()` only prints the path and not the `tree*`-chars in
the case of `--precise` and in this format the path is four spaces further
indented, i.e. on a newline, but on the same level as the path's children, i.e.
/nix/store/kn47hayxab8gc01jhr98dwyywbx561aq-nixos-system-roflmayr-21.11.20220207.6c202a9.drv
└───/: …1-p8.drv",["out"]),("/nix/store/g8bpgfjhh5vxrdq0w6r6s64f9kkm9z6c-etc.drv",["out"]),("/nix/store/…
→ /nix/store/g8bpgfjhh5vxrdq0w6r6s64f9kkm9z6c-etc.drv
As you can see `[...]-etc.drv` is a direct child of the root, but four
spaces indented. This logic was directly applied to the code-path with
`precise=false` which resulted in `tree*` being printed four spaces too
deep.
In case of no `--precise`, `hits[hash]` is empty and the path itself
should be printed rather than hits using the same logic as for `hits[hash]`.
With this fix, the output looks correct now:
/nix/store/kn47hayxab8gc01jhr98dwyywbx561aq-nixos-system-roflmayr-21.11.20220207.6c202a9.drv
└───/nix/store/g8bpgfjhh5vxrdq0w6r6s64f9kkm9z6c-etc.drv
├───/nix/store/hm0jmhp8shbf3cl846a685nv4f5cp3fy-nspawn-inst.drv
| [...]
└───/nix/store/2d6q3ygiim9ijl5d4h0qqx6vnjgxywyr-system-units.drv
└───/nix/store/dil014y1b8qyjhhhf5fpaah5fzdf0bzs-unit-systemd-nspawn-hydra.service.drv
└───/nix/store/a9r72wwx8qrxyp7hjydyg0gsrwnn26zb-activate.drv
└───/nix/store/99hlc7i4gl77wq087lbhag4hkf3kvssj-nixos-system-hydra-21.11pre-git.drv
It's a second attempt to merge the change. Previous attempt
was reverted in b976b34a5b.
Since then underlying failure exposed by original change was
fixed by https://github.com/NixOS/nix/pull/5354.
Below goes description of original change:
The link failure happens on a system with stable nix-2.3.15
installed in /usr/lib64 (it's libutil.so API differs from master):
```
LANG=C make V=1
g++ -o /home/slyfox/dev/git/nix/src/libstore/libnixstore.so \
-shared -L/usr/lib64 -Wl,--no-copy-dt-needed-entries \
src/libstore/binary-cache-store.o ... src/libstore/uds-remote-store.o \
-lsqlite3 -lcurl -lsodium -pthread -ldl -lseccomp -Wl,-z,defs -Wl,-soname=libnixstore.so
-Wl,-rpath,/home/slyfox/dev/git/nix/src/libutil -Lsrc/libutil -lnixutil
ld: src/libstore/binary-cache-store.o: in function `nix::BinaryCacheStore::BinaryCacheStore(
std::map<std::__cxx11::basic_string<char, std::char_traits<char>, ...
nix/src/libstore/binary-cache-store.cc:30: undefined reference to `nix::readFile(
std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)' ...
...
```
This happens due to `-L/usr/lib64 -Lsrc/libutil` search path ordering.
The change turns it into `-Lsrc/libutil -L/usr/lib64`.
Closes: https://github.com/NixOS/nix/issues/3087
This changes the representation of the interrupt callback list to
be safe to use during interrupt handling.
Holding a lock while executing arbitrary functions is something to
avoid in general, because of the risk of deadlock.
Such a deadlock occurs in https://github.com/NixOS/nix/issues/3294
where ~CurlDownloader tries to deregister its interrupt callback.
This happens during what seems to be a triggerInterrupt() by the
daemon connection's MonitorFdHup thread. This bit I can not confirm
based on the stack trace though; it's based on reading the code,
so no absolute certainty, but a smoking gun nonetheless.
