https://git.ruby-lang.org/ruby.git/commit/?id=3315ce6904

From 3315ce69044b511c7fe5d462985756a7948e95d1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?David=20Rodr=C3=ADguez?= <deivid.rodriguez@r...>
Date: Wed, 25 Mar 2020 21:22:00 +0100
Subject: [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

diff --git a/lib/rubygems/installer.rb b/lib/rubygems/installer.rb
index 241f541..cb212e9 100644
--- a/lib/rubygems/installer.rb
+++ b/lib/rubygems/installer.rb
@@ -509,7 +509,7 @@ class Gem::Installer https://github.com/ruby/ruby/blob/trunk/lib/rubygems/installer.rb#L509
   end
 
   def generate_plugins # :nodoc:
-    latest = Gem::Specification.latest_spec_for(spec.name)
+    latest = Gem::Installer.install_lock.synchronize { Gem::Specification.latest_spec_for(spec.name) }
     return if latest && latest.version > spec.version
 
     ensure_writable_dir @plugins_dir
-- 
cgit v0.10.2


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