From: KOSAKI Motohiro <kosaki.motohiro@...>
Date: 2011-06-18T21:14:50+09:00
Subject: [ruby-core:37218] Re: [Request for Comment] avoid timer thread

> From 9154363119cd09a3b79aa45753d177ec65914f7c Mon Sep 17 00:00:00 2001
> From: Eric Wong <normalperson@yhbt.net>
> Date: Fri, 17 Jun 2011 19:52:48 +0000
> Subject: [PATCH] defer timer thread wakeups after fork()
>
> There is a small race condition where a signal can be received
> immediately after fork() but before the timer thread pipe can be
> reinitialized, leading to EPIPE on write().
>
> We probably can't disable interrupt before forking due to
> system/exec() issues; and we don't want to lose wakeups to the
> parent process, so we check the cached pid vs getpid() whenever
> rb_thread_wakeup_timer_thread() is called.
> ---
> �thread_pthread.c | � 15 +++++++++++++++
> �1 files changed, 15 insertions(+), 0 deletions(-)
>
> diff --git a/thread_pthread.c b/thread_pthread.c
> index 1cc212b..3d99974 100644
> --- a/thread_pthread.c
> +++ b/thread_pthread.c
> @@ -989,11 +989,18 @@ static void ping_signal_thread_list(void) { }
> �#endif /* USE_SIGNAL_THREAD_LIST */
>
> �static pthread_t timer_thread_id;
> +static sig_atomic_t timer_thread_deferred;
> +static pid_t timer_thread_pid;
> �static int timer_thread_pipe[2];
>
> �void
> �rb_thread_wakeup_timer_thread(void)
> �{
> + � �if (getpid() != timer_thread_pid) {

getpid() return *process* id. timer thread and other threads will
get the same process id.