From d1f1ab1fc6bd80aabde23768534c3f698503a9d8 Mon Sep 17 00:00:00 2001 From: Eric Wong Date: Tue, 29 Dec 2015 10:48:18 +0000 Subject: [PATCH] thread_pthread.c (rb_thread_create_timer_thread): fix race This fixes an occasional [ASYNC BUG] failure in bootstraptest/test_fork.rb '[ruby-dev:37934]' which tests fork/pthread_create failure by setting RLIMIT_NPROC to 1 and triggering EAGAIN on pthread_create when attempting to recreate the timer thread. The problem timeline is as follows: thread 1 thread 2 --------------------------------------------------------------- rb_thread_create_timer_thread setup_communication_pipe rb_thread_wakeup_timer_thread_low pthread_create fails pipe looks valid, write! CLOSE_INVALIDATE (x4) EBADF -> ASYNC BUG The checks in rb_thread_wakeup_timer_thread_low only tried to guarantee proper ordering with native_stop_timer_thread, not rb_thread_create_timer_thread :x Now, this should allow rb_thread_create_timer_thread to synchronize properly with rb_thread_wakeup_timer_thread_low by delaying the validation marking of the timer_thread_pipe until we are certain the timer thread is alive. In this version, rb_thread_wakeup_timer_thread_low becomes a noop. Threading is still completely broken with NPROC==1, but there's not much we can do about it beside warn the user. We no longer spew a scary [ASYNC BUG] message at them and dump core on them. --- thread_pthread.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/thread_pthread.c b/thread_pthread.c index 2a15816..46cc571 100644 --- a/thread_pthread.c +++ b/thread_pthread.c @@ -1406,8 +1406,6 @@ setup_communication_pipe(void) return e; } - /* validate pipe on this process */ - timer_thread_pipe.owner_process = getpid(); return 0; } @@ -1615,6 +1613,9 @@ rb_thread_create_timer_thread(void) #endif return; } + + /* validate pipe on this process */ + timer_thread_pipe.owner_process = getpid(); timer_thread.created = 1; #ifdef HAVE_PTHREAD_ATTR_INIT pthread_attr_destroy(&attr); -- EW