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-rw-r--r--kernel/exit.c41
1 files changed, 33 insertions, 8 deletions
diff --git a/kernel/exit.c b/kernel/exit.c
index 84d13d6..1a0f10f 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1541,17 +1541,19 @@ static int wait_consider_task(struct wait_opts *wo, int ptrace,
if (p->exit_state == EXIT_DEAD)
return 0;
- if (likely(!ptrace) && unlikely(task_ptrace(p))) {
+ /* slay zombie? */
+ if (p->exit_state == EXIT_ZOMBIE) {
/*
- * This child is hidden by ptrace.
- * We aren't allowed to see it now, but eventually we will.
+ * A zombie ptracee is only visible to its ptracer.
+ * Notification and reaping will be cascaded to the real
+ * parent when the ptracer detaches.
*/
- wo->notask_error = 0;
- return 0;
- }
+ if (likely(!ptrace) && unlikely(task_ptrace(p))) {
+ /* it will become visible, clear notask_error */
+ wo->notask_error = 0;
+ return 0;
+ }
- /* slay zombie? */
- if (p->exit_state == EXIT_ZOMBIE) {
/* we don't reap group leaders with subthreads */
if (!delay_group_leader(p))
return wait_task_zombie(wo, p);
@@ -1580,15 +1582,38 @@ static int wait_consider_task(struct wait_opts *wo, int ptrace,
wo->notask_error = 0;
} else {
/*
+ * If @p is ptraced by a task in its real parent's group,
+ * hide group stop/continued state when looking at @p as
+ * the real parent; otherwise, a single stop can be
+ * reported twice as group and ptrace stops.
+ *
+ * If a ptracer wants to distinguish the two events for its
+ * own children, it should create a separate process which
+ * takes the role of real parent.
+ */
+ if (likely(!ptrace) && task_ptrace(p) &&
+ same_thread_group(p->parent, p->real_parent))
+ return 0;
+
+ /*
* @p is alive and it's gonna stop, continue or exit, so
* there always is something to wait for.
*/
wo->notask_error = 0;
}
+ /*
+ * Wait for stopped. Depending on @ptrace, different stopped state
+ * is used and the two don't interact with each other.
+ */
if (task_stopped_code(p, ptrace))
return wait_task_stopped(wo, ptrace, p);
+ /*
+ * Wait for continued. There's only one continued state and the
+ * ptracer can consume it which can confuse the real parent. Don't
+ * use WCONTINUED from ptracer. You don't need or want it.
+ */
return wait_task_continued(wo, p);
}
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