thread_sync.c: avoid reaching across stacks of dead threads

rb_ensure is insufficient cleanup for fork and we must
reinitialize all waitqueues in the child process.

Unfortunately this increases the footprint of ConditionVariable,
Queue and SizedQueue by 8 bytes on 32-bit (16 bytes on 64-bit).

[ruby-core:86316] [Bug #14634]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@62934 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 19 insertions, 0 deletions

diff --git a/test/thread/test_cv.rb b/test/thread/test_cv.rb
index 70cf4483a3..a093f373b1 100644
--- a/test/thread/test_cv.rb
+++ b/test/thread/test_cv.rb
@@ -219,4 +219,23 @@ INPUT
       Marshal.dump(condvar)
     end
   end
+
+  def test_condvar_fork
+    mutex = Mutex.new
+    condvar = ConditionVariable.new
+    thrs = (1..10).map do
+      Thread.new { mutex.synchronize { condvar.wait(mutex) } }
+    end
+    thrs.each { 3.times { Thread.pass } }
+    pid = fork do
+      mutex.synchronize { condvar.broadcast }
+      exit!(0)
+    end
+    _, s = Process.waitpid2(pid)
+    assert_predicate s, :success?, 'no segfault [ruby-core:86316] [Bug #14634]'
+    until thrs.empty?
+      mutex.synchronize { condvar.broadcast }
+      thrs.delete_if { |t| t.join(0.01) }
+    end
+  end if Process.respond_to?(:fork)
 end