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-rw-r--r--kernel/exit.c12
1 files changed, 9 insertions, 3 deletions
diff --git a/kernel/exit.c b/kernel/exit.c
index 1ea4369890a3..6806c55475ee 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1287,9 +1287,15 @@ static int wait_task_continued(struct wait_opts *wo, struct task_struct *p)
static int wait_consider_task(struct wait_opts *wo, int ptrace,
struct task_struct *p)
{
+ /*
+ * We can race with wait_task_zombie() from another thread.
+ * Ensure that EXIT_ZOMBIE -> EXIT_DEAD/EXIT_TRACE transition
+ * can't confuse the checks below.
+ */
+ int exit_state = ACCESS_ONCE(p->exit_state);
int ret;
- if (unlikely(p->exit_state == EXIT_DEAD))
+ if (unlikely(exit_state == EXIT_DEAD))
return 0;
ret = eligible_child(wo, p);
@@ -1310,7 +1316,7 @@ static int wait_consider_task(struct wait_opts *wo, int ptrace,
return 0;
}
- if (unlikely(p->exit_state == EXIT_TRACE)) {
+ if (unlikely(exit_state == EXIT_TRACE)) {
/*
* ptrace == 0 means we are the natural parent. In this case
* we should clear notask_error, debugger will notify us.
@@ -1337,7 +1343,7 @@ static int wait_consider_task(struct wait_opts *wo, int ptrace,
}
/* slay zombie? */
- if (p->exit_state == EXIT_ZOMBIE) {
+ if (exit_state == EXIT_ZOMBIE) {
/* we don't reap group leaders with subthreads */
if (!delay_group_leader(p)) {
/*