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authorOleg Nesterov <oleg@redhat.com>2012-06-20 12:53:04 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-06-20 14:39:36 -0700
commit50d75f8daead8a1f850c40a3b6c6575ab19b48cf (patch)
tree1917eec9deadded31869372207772d9a3d3ca11a
parent6347e90091041e34bea625370794c92f4ce71228 (diff)
pidns: find_new_reaper() can no longer switch to init_pid_ns.child_reaper
find_new_reaper() changes pid_ns->child_reaper, see add0d4df ("pid_ns: zap_pid_ns_processes: fix the ->child_reaper changing"). The original reason has gone away after the previous patch, ->children list must be empty after zap_pid_ns_processes(). However now we can not switch to init_pid_ns.child_reaper. __unhash_process() relies on the "->child_reaper == parent" check, but this check does not work if the last exiting task is also the child reaper. As Eric sugested, we can change __unhash_process() to use the parent's pid_ns and remove this code. Also, with this change we can move detach_pid(PIDTYPE_PID) back, where it was before the previous fix. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Louis Rilling <louis.rilling@kerlabs.com> Cc: Mike Galbraith <efault@gmx.de> Acked-by: Pavel Emelyanov <xemul@parallels.com> Tested-by: Andrew Wagin <avagin@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--kernel/exit.c10
1 files changed, 2 insertions, 8 deletions
diff --git a/kernel/exit.c b/kernel/exit.c
index a85efd2348b..2f59cc33451 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -64,6 +64,7 @@ static void exit_mm(struct task_struct * tsk);
static void __unhash_process(struct task_struct *p, bool group_dead)
{
nr_threads--;
+ detach_pid(p, PIDTYPE_PID);
if (group_dead) {
detach_pid(p, PIDTYPE_PGID);
detach_pid(p, PIDTYPE_SID);
@@ -78,13 +79,12 @@ static void __unhash_process(struct task_struct *p, bool group_dead)
if (IS_ENABLED(CONFIG_PID_NS)) {
struct task_struct *parent = p->real_parent;
- if ((task_active_pid_ns(p)->child_reaper == parent) &&
+ if ((task_active_pid_ns(parent)->child_reaper == parent) &&
list_empty(&parent->children) &&
(parent->flags & PF_EXITING))
wake_up_process(parent);
}
}
- detach_pid(p, PIDTYPE_PID);
list_del_rcu(&p->thread_group);
}
@@ -732,12 +732,6 @@ static struct task_struct *find_new_reaper(struct task_struct *father)
zap_pid_ns_processes(pid_ns);
write_lock_irq(&tasklist_lock);
- /*
- * We can not clear ->child_reaper or leave it alone.
- * There may by stealth EXIT_DEAD tasks on ->children,
- * forget_original_parent() must move them somewhere.
- */
- pid_ns->child_reaper = init_pid_ns.child_reaper;
} else if (father->signal->has_child_subreaper) {
struct task_struct *reaper;