From c299ff8c02c98cc2fc328ab51a0cb78cd98d0db8 Mon Sep 17 00:00:00 2001
From: Jean Boussier <jean.boussier@gmail.com>
Date: Mon, 20 Nov 2023 12:13:45 +0100
Subject: [PATCH] Drop dependency on mutex_m

In Ruby 3.3.0 `mutex_m` is promoted to a default gem, which requires
to add it to the gemspec/gemfile.

But given how little usage it has in `concurrent-ruby` I think it might
as well just be not used.

Additionally including `Mutex_m` cause many undesirable methods to
be exposed, so simply using a Mutex instance variable is preferable.
---
 .../map/synchronized_map_backend.rb           | 43 ++++++++++---------
 1 file changed, 23 insertions(+), 20 deletions(-)

diff --git a/lib/concurrent-ruby/concurrent/collection/map/synchronized_map_backend.rb b/lib/concurrent-ruby/concurrent/collection/map/synchronized_map_backend.rb
index 190c8d98d..efa161ed9 100644
--- a/lib/concurrent-ruby/concurrent/collection/map/synchronized_map_backend.rb
+++ b/lib/concurrent-ruby/concurrent/collection/map/synchronized_map_backend.rb
@@ -8,74 +8,77 @@ module Collection
     # @!visibility private
     class SynchronizedMapBackend < NonConcurrentMapBackend
 
-      require 'mutex_m'
-      include Mutex_m
-      # WARNING: Mutex_m is a non-reentrant lock, so the synchronized methods are
-      # not allowed to call each other.
+      def initialize(*args, &block)
+        super
+
+        # WARNING: Mutex is a non-reentrant lock, so the synchronized methods are
+        # not allowed to call each other.
+        @mutex = Mutex.new
+      end
 
       def [](key)
-        synchronize { super }
+        @mutex.synchronize { super }
       end
 
       def []=(key, value)
-        synchronize { super }
+        @mutex.synchronize { super }
       end
 
       def compute_if_absent(key)
-        synchronize { super }
+        @mutex.synchronize { super }
       end
 
       def compute_if_present(key)
-        synchronize { super }
+        @mutex.synchronize { super }
       end
 
       def compute(key)
-        synchronize { super }
+        @mutex.synchronize { super }
       end
 
       def merge_pair(key, value)
-        synchronize { super }
+        @mutex.synchronize { super }
       end
 
       def replace_pair(key, old_value, new_value)
-        synchronize { super }
+        @mutex.synchronize { super }
       end
 
       def replace_if_exists(key, new_value)
-        synchronize { super }
+        @mutex.synchronize { super }
       end
 
       def get_and_set(key, value)
-        synchronize { super }
+        @mutex.synchronize { super }
       end
 
       def key?(key)
-        synchronize { super }
+        @mutex.synchronize { super }
       end
 
       def delete(key)
-        synchronize { super }
+        @mutex.synchronize { super }
       end
 
       def delete_pair(key, value)
-        synchronize { super }
+        @mutex.synchronize { super }
       end
 
       def clear
-        synchronize { super }
+        @mutex.synchronize { super }
       end
 
       def size
-        synchronize { super }
+        @mutex.synchronize { super }
       end
 
       def get_or_default(key, default_value)
-        synchronize { super }
+        @mutex.synchronize { super }
       end
 
       private
       def dupped_backend
-        synchronize { super }
+        @mutex.synchronize { super }
       end
     end
   end