normal	2017-05-25 03:59:24 +0900 (Thu, 25 May 2017)

  New Revision: 58874

  https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=58874

  Log:
    thread_pthread: retry timer thread creation w/o attr on EINVAL
    
    Setting a small stack size can fail due to having 3rd-party
    libraries (e.g. libkqueue) loaded, if those libraries use
    thread-local-storage (__thread) heavily.  This causes
    pthread_create to fail with small stacks; even if our
    timer_thread function does not hit any of the TLS-using code
    paths.
    
    Today, some RubyGems are capable of using libkqueue (or __thread
    storage directly), and future versions of Ruby may use kqueue
    internally.
    
    cf. https://www.akkadia.org/drepper/tls.pdf

  Modified files:
    trunk/thread_pthread.c
Index: thread_pthread.c
===================================================================
--- thread_pthread.c	(revision 58873)
+++ thread_pthread.c	(revision 58874)
@@ -1587,6 +1587,7 @@ rb_thread_create_timer_thread(void) https://github.com/ruby/ruby/blob/trunk/thread_pthread.c#L1587
 	int err;
 #ifdef HAVE_PTHREAD_ATTR_INIT
 	pthread_attr_t attr;
+	rb_vm_t *vm = GET_VM();
 
 	err = pthread_attr_init(&attr);
 	if (err != 0) {
@@ -1623,10 +1624,20 @@ rb_thread_create_timer_thread(void) https://github.com/ruby/ruby/blob/trunk/thread_pthread.c#L1624
 	    rb_bug("rb_thread_create_timer_thread: Timer thread was already created\n");
 	}
 #ifdef HAVE_PTHREAD_ATTR_INIT
-	err = pthread_create(&timer_thread.id, &attr, thread_timer, &GET_VM()->gvl);
+	err = pthread_create(&timer_thread.id, &attr, thread_timer, &vm->gvl);
 	pthread_attr_destroy(&attr);
+
+	if (err == EINVAL) {
+	    /*
+	     * Even if we are careful with our own stack use in thread_timer(),
+	     * any third-party libraries (eg libkqueue) which rely on __thread
+	     * storage can cause small stack sizes to fail.  So lets hope the
+	     * default stack size is enough for them:
+	     */
+	    err = pthread_create(&timer_thread.id, NULL, thread_timer, &vm->gvl);
+	}
 #else
-	err = pthread_create(&timer_thread.id, NULL, thread_timer, &GET_VM()->gvl);
+	err = pthread_create(&timer_thread.id, NULL, thread_timer, &vm->gvl);
 #endif
 	if (err != 0) {
 	    rb_warn("pthread_create failed for timer: %s, scheduling broken",

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