shared memory deadlock between git commands launched in same shell

[ConceptualWempa]

• [✓] I was not able to find an open or closed issue matching what I'm seeing

Setup

• Which version of Git for Windows are you using? Is it 32-bit or 64-bit?

64-bit

$ git --version --build-options

git --version --build-options
git version 2.47.0.windows.2
cpu: x86_64
built from commit: 1f8a83c
sizeof-long: 4
sizeof-size_t: 8
shell-path: D:/git-sdk-64-build-installers/usr/bin/sh
feature: fsmonitor--daemon
libcurl: 8.10.1
OpenSSL: OpenSSL 3.2.3 3 Sep 2024
zlib: 1.3.1

• Which version of Windows are you running? Vista, 7, 8, 10? Is it 32-bit or 64-bit?

10, 64-bit

$ cmd.exe /c ver

Microsoft Windows [Version 10.0.19045.5011]

• What options did you set as part of the installation? Or did you choose the
  defaults?

defaults, except default branch name

One of the following:

type "C:\Program Files\Git\etc\install-options.txt"
type "C:\Program Files (x86)\Git\etc\install-options.txt"
type "%USERPROFILE%\AppData\Local\Programs\Git\etc\install-options.txt"
type "$env:USERPROFILE\AppData\Local\Programs\Git\etc\install-options.txt"
$ cat /etc/install-options.txt

cat /etc/install-options.txt
Editor Option: VIM
Custom Editor Path:
Default Branch Option: main
Path Option: Cmd
SSH Option: OpenSSH
Tortoise Option: false
CURL Option: OpenSSL
CRLF Option: CRLFCommitAsIs
Bash Terminal Option: MinTTY
Git Pull Behavior Option: Merge
Use Credential Manager: Enabled
Performance Tweaks FSCache: Enabled
Enable Symlinks: Disabled
Enable FSMonitor: Disabled

• Any other interesting things about your environment that might be related
  to the issue you're seeing?

None that I'm aware of.

Details

• Which terminal/shell are you running Git from? e.g Bash/CMD/PowerShell/other

Git Bash

• What commands did you run to trigger this issue? If you can provide a
  Minimal, Complete, and Verifiable example
  this will help us understand the issue.

git gui &
git log

• What did you expect to occur after running these commands?

git log should've printed usual output

• What actually happened instead?

git log hangs with no output ... upon ctrl-c, something similar to follow is printed:

  0 [] less 2283 C:\Program Files\Git\usr\bin\less.exe: *** fatal error - Can't reopen shared memory during exec, Win32 error 6

• If the problem was occurring with a specific repository, can you provide the URL to that repository to help us with testing?

does not appear to be related to a specific repo ... although, perhaps significantly, 'git init ...' in the same shell does NOT hang, and 'git log' in the resulting empty workspace prints:
fatal: your current branch 'main' does not have any commits yet
as expected ... 'git status' and 'git add' also work, but 'git commit' hangs and ctrl-c elicits similar output (except the program reported is ...\usr\bin\sh.exe)

[dscho]

Hmm. I cannot reproduce. In a freshly-initialized worktree:

$ git gui &
[3] 2215

$  git log
fatal: your current branch 'main' does not have any commits yet

[ConceptualWempa]

@dscho try with a non-empty repo - I saw the same result with an empty one while experimenting, suppose I should've specified that "the usual output" meant at least one commit, i.e. a non-empty repo.

[tda-ableton]

I'm running into issue this after upgrading from 2.44.1 to 2.47.1.windows.2.

I'm working in a cmd.exe and I usually open git gui from there. As soon as it's open, many git commands like git log, git stash list, or git rebase -i ... hang. On Ctrl-C, they will print

      0 [] less 1451 C:\Program Files\Git\usr\bin\less.exe: *** fatal error - Can't reopen shared memory during exec, Win32 error 6

(for git log or git stash list) or

      0 [] nano 1453 C:\Program Files\Git\usr\bin\nano.exe: *** fatal error - Can't reopen shared memory during exec, Win32 error 6
      0 [] sh 1454 C:\Program Files\Git\usr\bin\sh.exe: *** fatal error - Can't reopen shared memory during exec, Win32 error 6

(for git rebase -i; I've nano configured as my editor).

I then tried again with a fresh empty repo: Opening git gui from the terminal first.
Then, git log and git stash list don't hang, presumably because there's nothing to show in an empty repo, so they don't need to invoke less.exe.
But when I attempt to commit something, git commit shows the same behavior as described above: Hanging on hint: Waiting for your editor to close the file... and on Ctrl-C I get

       1 [] sh 1456 C:\Program Files\Git\usr\bin\sh.exe: *** fatal error - Can't reopen shared memory during exec, Win32 error 6
       0 [] nano 1458 C:\Program Files\Git\usr\bin\nano.exe: *** fatal error - Can't reopen shared memory during exec, Win32 error 6
Aborting commit due to empty commit message.

Happy to provide more info about my setup if needed.

[tda-ableton]

Upgrading to 2.48.1 seems to have fixed this issue for me. I don't see anything related to it in the release notes specific to Git for Windows, but maybe something changed in upstream Git that fixed it.

[dscho]

Could potentially be this:

-msys2-runtime 3.5.4-2
+msys2-runtime 3.5.7-1