signals: document CLD_CONTINUED notification mechanics
A couple of small comments about how CLD_CONTINUED notification works.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/signal.c b/kernel/signal.c
index 359c4de..8423867 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -633,6 +633,11 @@
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 @@
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;