Hacktoberfest 2026：维护者为十月标记出来的 issue，仍然开放、适合新手。 浏览 Hacktoberfest issue

SPLICE_F_NONBLOCK can block on a pipe shared with another process

未关闭
  • 哪里不对？
#473 0 条评论 0 个 reaction 已指派 0 人 在 GitHub 查看

维护者通常 3 天内回复

还没有人认领这个 Issue。

评估

难度
5/5
预计耗时
一周以上
新手友好度
35/100
Issue 类型
缺陷
描述清晰度
基本清楚
活跃度
活跃
技术栈
c, macos
领域
operating-systems

调研方向

Start in src/syscall/io.c and read the io_xfer, io_xfer_once, sys_splice, and splice_drain_chunk paths described in the issue. Compare the input and output pipe races, then investigate macOS pipe APIs for a per-operation nonblocking transfer that preserves data already read. Done means SPLICE_F_NONBLOCK returns without parking the vCPU in both races, without changing nonblocking behavior for other processes sharing the pipe.

由索引模型根据 Issue 内容生成。

描述

bug

splice with SPLICE_F_NONBLOCK can still block when another process works on the same pipe between a readiness check and the host transfer. There are two windows, both in src/syscall/io.c:

  • Input: on a pipe that elfuse does not own (for example inherited stdin), io_xfer answers a per-call nonblocking read with poll(0) and then a plain read. When a sibling process drains the pipe between the two calls and the writer stays open, the read parks the vCPU thread, so the splice hangs instead of returning EAGAIN, and guest signal and teardown checks cannot run. A socket input is not affected, because io_xfer_once already passes MSG_DONTWAIT.
  • Output: before each read, sys_splice checks the output pipe's free room with poll and fstat, but that reserves nothing. When another writer fills the pipe between the check and the write, the chunk has already been read, and splice_drain_chunk blocks in io_xfer on the output despite the flag.

Linux holds the pipe lock across the check and the transfer. macOS has no per-call nonblocking read or write for a pipe, and setting O_NONBLOCK on the description would change it for every process that shares it. Making the output write nonblocking would close the second window, but it would lose the chunk already taken from a pipe or socket input.

Found in review on #463, where both windows are now stated in the code comments.

主要语言
C
星标
278
派生
31
平均合并
2 天 22 小时
30 天内合并 PR
18

环境准备

  • 没有 Dockerfile 或 Docker Compose 文件
  • 没有 Pull Request 模板
  • 阅读贡献指南

从这里开始

  1. 先读完整个 Issue，再读项目的贡献指南。
  2. 在 Issue 下留言说明你要接手 —— 这能避免两个人做同样的事。
  3. Fork 仓库，在一个分支上完成修改。
  4. 提交 Pull Request，并在描述里引用这个 Issue 编号。

sysprog21/elfuse 的其他 Issue

查看 sysprog21/elfuse 的全部 Issue

相似的 Issue

更多 C Issue

把新 issue 发到你的邮箱

精选适合新手参与的 GitHub issue 摘要。