Correct method to unlock a suspended upgrade?

[shallow-beach]

Output of brew config

HOMEBREW_VERSION: 5.0.14
ORIGIN: https://github.com/Homebrew/brew
HEAD: 6e88ffd4d26b5074cdbcad13f7dcff4222e8677f
Last commit: 7 days ago
Branch: stable
Core tap JSON: 16 Feb 01:07 UTC
Core cask tap JSON: 16 Feb 01:07 UTC
HOMEBREW_PREFIX: /opt/homebrew
HOMEBREW_CASK_OPTS: []
HOMEBREW_DISPLAY: /private/tmp/com.apple.launchd.dBYxn6j8fi/org.xquartz:0
HOMEBREW_DOWNLOAD_CONCURRENCY: 22
HOMEBREW_FORBID_PACKAGES_FROM_PATHS: set
HOMEBREW_MAKE_JOBS: 11
Homebrew Ruby: 3.4.8 => /opt/homebrew/Library/Homebrew/vendor/portable-ruby/3.4.8/bin/ruby
CPU: 11-core 64-bit arm_lobos
Clang: 17.0.0 build 1700
Git: 2.52.0 => /opt/homebrew/bin/git
Curl: 8.7.1 => /usr/bin/curl
macOS: 26.3-arm64
CLT: 26.2.0.0.1.1764812424
Xcode: 26.2
Metal Toolchain: N/A
Rosetta 2: false

Output of brew doctor

Please note that these warnings are just used to help the Homebrew maintainers
with debugging if you file an issue. If everything you use Homebrew for is
working fine: please don't worry or file an issue; just ignore this. Thanks!

Warning: Some installed formulae are deprecated or disabled.
You should find replacements for the following formulae:
  icu4c@77

Description of issue

I ran a brew upgrade, and while the rest of the fetched package downloads were running at 1-100 MB/s, the gcc upgrade from 15.2.0 -> 15.2.0_1 was only downloading at ~100KB/s.

I figured something went wrong so I suspended the process with Ctrl+C. This gave me zsh: suspended brew upgrade. Now, after running brew upgrade, I get the following error:

Error: A `brew upgrade` process has already locked /Users/<username>/Library/Caches/Homebrew/downloads/9a2643182c3aa146f2aed0f6af58fab3af182d65f425373ecfd3569d6a1dc492--gcc--15.2.0_1.arm64_tahoe.bottle.tar.gz.incomplete.
Please wait for it to finish or terminate it to continue.

And later:

Error: No such file or directory @ rb_sysopen - /Users/<username>/Library/Caches/Homebrew/downloads/9a2643182c3aa146f2aed0f6af58fab3af182d65f425373ecfd3569d6a1dc492--gcc--15.2.0_1.arm64_tahoe.bottle.tar.gz

I've waited about an hour, and still get the same errors. What is the recommended/safest method to fix this issue?

[botantony]

I ran a brew upgrade, and while the rest of the fetched package downloads were running at 1-100 MB/s, the gcc upgrade from 15.2.0 -> 15.2.0_1 was only downloading at ~100KB/s.

This seems to be a bug, although I'm not sure how to reproduce it. Try to clear Homebrew cache (brew cleanup --prune=all) and run brew upgrade again