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Subject[PATCH 6/6] exit: reparent: introduce find_alive_thread()
Add the new simple helper to factor out the for_each_thread() code
in find_child_reaper() and find_new_reaper(). It can also simplify
the potential PF_EXITING -> exit_state change, plus perhaps we can
change this code to take SIGNAL_GROUP_EXIT into account.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
kernel/exit.c | 32 +++++++++++++++++++-------------
1 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/kernel/exit.c b/kernel/exit.c
index 00c6139..4e3475d 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -459,6 +459,17 @@ static void exit_mm(struct task_struct *tsk)
clear_thread_flag(TIF_MEMDIE);
}

+static struct task_struct *find_alive_thread(struct task_struct *p)
+{
+ struct task_struct *t;
+
+ for_each_thread(p, t) {
+ if (!(t->flags & PF_EXITING))
+ return t;
+ }
+ return NULL;
+}
+
static struct task_struct *find_child_reaper(struct task_struct *father)
__releases(&tasklist_lock)
__acquires(&tasklist_lock)
@@ -469,9 +480,8 @@ static struct task_struct *find_child_reaper(struct task_struct *father)
if (likely(reaper != father))
return reaper;

- for_each_thread(father, reaper) {
- if (reaper->flags & PF_EXITING)
- continue;
+ reaper = find_alive_thread(father);
+ if (reaper) {
pid_ns->child_reaper = reaper;
return reaper;
}
@@ -497,16 +507,13 @@ static struct task_struct *find_child_reaper(struct task_struct *father)
static struct task_struct *find_new_reaper(struct task_struct *father,
struct task_struct *child_reaper)
{
- struct task_struct *thread;
+ struct task_struct *thread, *reaper;

- for_each_thread(father, thread) {
- if (thread->flags & PF_EXITING)
- continue;
+ thread = find_alive_thread(father);
+ if (thread)
return thread;
- }

if (father->signal->has_child_subreaper) {
- struct task_struct *reaper;
/*
* Find the first ->is_child_subreaper ancestor in our pid_ns.
* We start from father to ensure we can not look into another
@@ -520,10 +527,9 @@ static struct task_struct *find_new_reaper(struct task_struct *father,
break;
if (!reaper->signal->is_child_subreaper)
continue;
- for_each_thread(reaper, thread) {
- if (!(thread->flags & PF_EXITING))
- return thread;
- }
+ thread = find_alive_thread(reaper);
+ if (thread)
+ return thread;
}
}

--
1.5.5.1


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