From 021e1ae3d85a76ce962a300c96813f04ae50c87c Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Wed, 30 Apr 2008 00:53:00 -0700 Subject: signals: document CLD_CONTINUED notification mechanics A couple of small comments about how CLD_CONTINUED notification works. Signed-off-by: Oleg Nesterov Cc: Roland McGrath Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/signal.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/kernel/signal.c b/kernel/signal.c index 359c4de7c77..8423867f7d8 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -633,6 +633,11 @@ static int prepare_signal(int sig, struct task_struct *p) why |= SIGNAL_CLD_STOPPED; if (why) { + /* + * The first thread which returns from finish_stop() + * will take ->siglock, notice SIGNAL_CLD_MASK, and + * notify its parent. See get_signal_to_deliver(). + */ signal->flags = why | SIGNAL_STOP_CONTINUED; signal->group_stop_count = 0; signal->group_exit_code = 0; @@ -1694,7 +1699,11 @@ relock: try_to_freeze(); spin_lock_irq(&sighand->siglock); - + /* + * Every stopped thread goes here after wakeup. Check to see if + * we should notify the parent, prepare_signal(SIGCONT) encodes + * the CLD_ si_code into SIGNAL_CLD_MASK bits. + */ if (unlikely(signal->flags & SIGNAL_CLD_MASK)) { int why = (signal->flags & SIGNAL_STOP_CONTINUED) ? CLD_CONTINUED : CLD_STOPPED; -- cgit v1.2.3