[rubygems/rubygems] Fix race condition on bundler's parallel installer

When installing in parallel, bundler creates several `Gem::Installer`
instances that run in parallel. These installers access the `@@all` class
variable of `Gem::Specification` concurrently.

If a concurrent thread calls `Gem::Specification.reset` (resetting
`@all` to `nil`) while another thread is running
`Gem::Specification._all` or another method that expects `@@all` to be
loaded and not `nil`, that can result in `Enumerable` methods being
called on `nil`, resulting in crashes.

I fix it by protecting the other concurrent access to the `@all`
variable.

https://github.com/rubygems/rubygems/commit/58b343c530

0 files changed, 0 insertions, 0 deletions