Fix deadlocks, small improvements

lib/redis/semaphore.rb

@@ -19,13 +19,17 @@ def initialize(name, opts = {})
       @expiration = opts.delete(:expiration)
       @resource_count = opts.delete(:resources) || 1
       @stale_client_timeout = opts.delete(:stale_client_timeout)
-      @redis = opts.delete(:redis) || Redis.new(opts)
       @use_local_time = opts.delete(:use_local_time)
+      @redis = if @redis = opts.delete(:redis)
+                 @redis.dup
+               else
+                 Redis.new(opts)
+               end
       @tokens = []
     end
 
     def exists_or_create!
-      token = @redis.getset(exists_key, EXISTS_TOKEN)
+      token = @redis.get(exists_key)
 
       if token.nil?
         create!
@@ -90,11 +94,7 @@ def locked?(token = nil)
       if token
         @redis.hexists(grabbed_key, token)
       else
-        @tokens.each do |token|
-          return true if locked?(token)
-        end
-
-        false
+        @tokens.any? { |t| locked?(t) }
       end
     end
 
@@ -156,7 +156,7 @@ def simple_mutex(key_name, expires = nil)
     end
 
     def create!
-      @redis.expire(exists_key, 10)
+      @redis.setex(exists_key, 10, EXISTS_TOKEN)
 
       @redis.multi do
         @redis.del(grabbed_key)

spec/semaphore_spec.rb

@@ -125,6 +125,23 @@
 
       expect(@redis.keys.count).to eq(original_key_size)
     end
+
+    it "don't enters deadlock" do
+      i = 0
+      expect {
+        redis = @redis.dup
+        Timeout.timeout(2) do
+          Array.new(2).map do
+            Thread.new do
+              Redis::Semaphore.new(:sem, redis: redis).lock do
+                i += 1
+              end
+            end
+          end.each(&:join)
+        end
+      }.not_to raise_error
+      expect(i).to eq(2)
+    end
   end
 
   describe "semaphore with expiration" do
@@ -211,7 +228,8 @@
     end
 
     it "without time support should return the same time as frozen time" do
-      expect(@redis).to receive(:time).and_raise(Redis::CommandError)
+      expect(semaphore.instance_variable_get(:@redis)).to receive(:time)
+        .and_raise(Redis::CommandError)
       expect(semaphore.send(:current_time)).to eq(Time.now)
     end
   end

spec/spec_helper.rb

@@ -4,4 +4,5 @@
 
 $TESTING=true
 $:.unshift File.join(File.dirname(__FILE__), '..', 'lib')
+require 'timeout'
 require 'redis/semaphore'