212bf2b702
When a remote SSH client disconnects during a long-running operation
like addToStore(), the nix-daemon can deadlock in a circular wait:
- Process A (SSH daemon): blocked reading from downstream store socket,
waiting for response from local daemon
- Process B (local daemon): blocked reading from upstream socket,
waiting for more NAR data from SSH daemon
The existing interrupt mechanism (ReceiveInterrupts + MonitorFdHup)
correctly detects the SSH disconnect and sets _isInterrupted, but the
daemon remains blocked in read() on the downstream store connection.
Even though SIGUSR1 causes read() to return EINTR, the circular
dependency prevents forward progress.
Fix this by adding shutdownConnections() to RemoteStore that calls
shutdown(fd, SHUT_RDWR) on all tracked connection file descriptors.
Register an interrupt callback in processConnection() that invokes
this method when the store is a RemoteStore. This causes any blocking
read() to return 0 (EOF), breaking the circular wait and allowing
both processes to exit cleanly.
The fix tracks connection FDs in a synchronized set, populated when
connections are created by the Pool factory. On interrupt, all FDs
are shut down regardless of whether they're idle or in-use.
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|---|---|---|
| .github | ||
| ci/gha | ||
| contrib | ||
| doc/manual | ||
| maintainers | ||
| misc | ||
| nix-meson-build-support | ||
| packaging | ||
| scripts | ||
| src | ||
| tests | ||
| .clang-format | ||
| .clang-tidy | ||
| .coderabbit.yaml | ||
| .dir-locals.el | ||
| .editorconfig | ||
| .git-blame-ignore-revs | ||
| .gitignore | ||
| .shellcheckrc | ||
| .version | ||
| CITATION.cff | ||
| CONTRIBUTING.md | ||
| COPYING | ||
| default.nix | ||
| docker.nix | ||
| flake.lock | ||
| flake.nix | ||
| HACKING.md | ||
| meson.build | ||
| meson.format | ||
| meson.options | ||
| README.md | ||
| shell.nix | ||
Nix
Nix is a powerful package manager for Linux and other Unix systems that makes package management reliable and reproducible. Please refer to the Nix manual for more details.
Installation and first steps
Visit nix.dev for installation instructions and beginner tutorials.
Full reference documentation can be found in the Nix manual.
Building and developing
Follow instructions in the Nix reference manual to set up a development environment and build Nix from source.
Contributing
Check the contributing guide if you want to get involved with developing Nix.
Additional resources
Nix was created by Eelco Dolstra and developed as the subject of his PhD thesis The Purely Functional Software Deployment Model, published 2006. Today, a world-wide developer community contributes to Nix and the ecosystem that has grown around it.
- The Nix, Nixpkgs, NixOS Community on nixos.org
- Official documentation on nix.dev
- Nixpkgs is the largest, most up-to-date free software repository in the world
- NixOS is a Linux distribution that can be configured fully declaratively
- Discourse
- Matrix: #users:nixos.org for user support and #nix-dev:nixos.org for development
License
Nix is released under the LGPL v2.1.