merge revision(s) 62668: [Backport #14578]

	thread.c: reset waitq of keeping mutexes in child

	We must not maintain references to threads in the parent process
	in any mutexes held by the child process.

	* thread_sync.c (rb_mutex_cleanup_keeping_mutexes): new function
	* thread.c (rb_thread_atfork): cleanup keeping mutexes
	  [ruby-core:85940] [Bug #14578]

	Fixes: r58604 (commit 3586c9e0876e784767a1c1adba9ebc2499fa0ec2)
	       ("reduce rb_mutex_t size from 160 to 80 bytes on 64-bit")

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_5@62852 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

4 files changed, 27 insertions, 1 deletions

diff --git a/test/ruby/test_thread.rb b/test/ruby/test_thread.rb
index 591292962d..135d17237e 100644
--- a/test/ruby/test_thread.rb
+++ b/test/ruby/test_thread.rb
@@ -1188,6 +1188,17 @@ q.pop
     assert_predicate(status, :success?, bug9751)
   end if Process.respond_to?(:fork)
 
+  def test_fork_while_locked
+    m = Mutex.new
+    thrs = []
+    3.times do |i|
+      thrs << Thread.new { m.synchronize { Process.waitpid2(fork{})[1] } }
+    end
+    thrs.each do |t|
+      assert_predicate t.value, :success?, '[ruby-core:85940] [Bug #14578]'
+    end
+  end if Process.respond_to?(:fork)
+
   def test_subclass_no_initialize
     t = Module.new do
       break eval("class C\u{30b9 30ec 30c3 30c9} < Thread; self; end")
diff --git a/thread.c b/thread.c
index 9f2267a1f4..fad0ce6efc 100644
--- a/thread.c
+++ b/thread.c
@@ -4208,6 +4208,7 @@ rb_thread_atfork(void)
     rb_thread_t *th = GET_THREAD();
     rb_thread_atfork_internal(th, terminate_atfork_i);
     th->join_list = NULL;
+    rb_mutex_cleanup_keeping_mutexes(th);
 
     /* We don't want reproduce CVE-2003-0900. */
     rb_reset_random_seed();
diff --git a/thread_sync.c b/thread_sync.c
index b4970e507c..ef0bbf3af3 100644
--- a/thread_sync.c
+++ b/thread_sync.c
@@ -415,6 +415,20 @@ rb_mutex_abandon_all(rb_mutex_t *mutexes)
 	list_head_init(&mutex->waitq);
     }
 }
+
+/*
+ * All other threads are dead in the a new child process, so waitqs
+ * contain references to dead threads which we need to clean up
+ */
+static void
+rb_mutex_cleanup_keeping_mutexes(const rb_thread_t *current_thread)
+{
+    rb_mutex_t *mutex = current_thread->keeping_mutexes;
+    while (mutex) {
+        list_head_init(&mutex->waitq);
+        mutex = mutex->next_mutex;
+    }
+}
 #endif
 
 static VALUE
diff --git a/version.h b/version.h
index 33fb4e79ee..0a58882496 100644
--- a/version.h
+++ b/version.h
@@ -1,6 +1,6 @@
 #define RUBY_VERSION "2.5.0"
 #define RUBY_RELEASE_DATE "2018-03-19"
-#define RUBY_PATCHLEVEL 42
+#define RUBY_PATCHLEVEL 43
 
 #define RUBY_RELEASE_YEAR 2018
 #define RUBY_RELEASE_MONTH 3