[PATCH 15/23] tracehook: job control

Roland McGrath
2008-07-17T07:33:28Z

This defines the tracehook_notify_jctl() hook to formalize
the ptrace effects on the job control notifications.
There is no change, only cleanup.

Signed-off-by: Roland McGrath <roland@redhat.com>
---
include/linux/tracehook.h | 20 ++++++++++++++++++++
kernel/signal.c | 10 +++++-----
2 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h
index 42a0d7b..6dc428d 100644
--- a/include/linux/tracehook.h
+++ b/include/linux/tracehook.h
@@ -451,4 +451,24 @@ static inline int tracehook_get_signal(struct task_struct *task,
return 0;
}

+/**
+ * tracehook_notify_jctl - report about job control stop/continue
+ * @notify: nonzero if this is the last thread in the group to stop
+ * @why: %CLD_STOPPED or %CLD_CONTINUED
+ *
+ * This is called when we might call do_notify_parent_cldstop().
+ * It's called when about to stop for job control; we are already in
+ * %TASK_STOPPED state, about to call schedule(). It's also called when
+ * a delayed %CLD_STOPPED or %CLD_CONTINUED report is ready to be made.
+ *
+ * Return nonzero to generate a %SIGCHLD with @why, which is
+ * normal if @notify is nonzero.
+ *
+ * Called with no locks held.
+ */
+static inline int tracehook_notify_jctl(int notify, int why)
+{
+ return notify || (current->ptrace & PT_PTRACED);
+}
+
#endif /* <linux/tracehook.h> */
diff --git a/kernel/signal.c b/kernel/signal.c
index 1766c47..9b8d94a 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -605,9 +605,6 @@ static int check_kill_permission(int sig, struct siginfo *info,
return security_task_kill(t, info, sig, 0);
}

-/* forward decl */
-static void do_notify_parent_cldstop(struct task_struct *tsk, int why);
-
/*
* Handle magic process-wide effects of stop/continue signals. Unlike
* the signal actions, these happen immediately at signal-generation
@@ -1629,7 +1626,7 @@ finish_stop(int stop_count)
* a group stop in progress and we are the last to stop,
* report to the parent. When ptraced, every thread reports itself.
*/
- if (stop_count == 0 || (current->ptrace & PT_PTRACED)) {
+ if (tracehook_notify_jctl(stop_count == 0, CLD_STOPPED)) {
read_lock(&tasklist_lock);
do_notify_parent_cldstop(current, CLD_STOPPED);
read_unlock(&tasklist_lock);
@@ -1766,6 +1763,9 @@ relock:
signal->flags &= ~SIGNAL_CLD_MASK;
spin_unlock_irq(&sighand->siglock);

+ if (unlikely(!tracehook_notify_jctl(1, why)))
+ goto relock;
+
read_lock(&tasklist_lock);
do_notify_parent_cldstop(current->group_leader, why);
read_unlock(&tasklist_lock);
@@ -1931,7 +1931,7 @@ void exit_signals(struct task_struct *tsk)
out:
spin_unlock_irq(&tsk->sighand->siglock);

- if (unlikely(group_stop)) {
+ if (unlikely(group_stop) && tracehook_notify_jctl(1, CLD_STOPPED)) {
read_lock(&tasklist_lock);
do_notify_parent_cldstop(tsk, CLD_STOPPED);
read_unlock(&tasklist_lock);