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pidns: Wait in zap_pid_ns_processes until pid_ns->nr_hashed == 1

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Looking at pid_ns->nr_hashed is a bit simpler and it works for
disjoint process trees that an unshare or a join of a pid_namespace
may create.

Acked-by: "Serge E. Hallyn" <serge@hallyn.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2012-08-01 15:03:42 -07:00
parent 5e1182deb8
commit af4b8a83ad
3 changed files with 17 additions and 26 deletions
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12
kernel/exit.c
View File

@ -72,18 +72,6 @@ static void __unhash_process(struct task_struct *p, bool group_dead)
list_del_rcu(&p->tasks);
list_del_init(&p->sibling);
__this_cpu_dec(process_counts);
/*
* If we are the last child process in a pid namespace to be
* reaped, notify the reaper sleeping zap_pid_ns_processes().
*/
if (IS_ENABLED(CONFIG_PID_NS)) {
struct task_struct *parent = p->real_parent;
if ((task_active_pid_ns(parent)->child_reaper == parent) &&
list_empty(&parent->children) &&
(parent->flags & PF_EXITING))
wake_up_process(parent);
}
}
list_del_rcu(&p->thread_group);
}

16
kernel/pid.c
View File

@ -273,10 +273,20 @@ void free_pid(struct pid *pid)
spin_lock_irqsave(&pidmap_lock, flags);
for (i = 0; i <= pid->level; i++) {
struct upid *upid = pid->numbers + i;
struct pid_namespace *ns = upid->ns;
hlist_del_rcu(&upid->pid_chain);
if (--upid->ns->nr_hashed == 0) {
upid->ns->nr_hashed = -1;
schedule_work(&upid->ns->proc_work);
switch(--ns->nr_hashed) {
case 1:
/* When all that is left in the pid namespace
* is the reaper wake up the reaper. The reaper
* may be sleeping in zap_pid_ns_processes().
*/
wake_up_process(ns->child_reaper);
break;
case 0:
ns->nr_hashed = -1;
schedule_work(&ns->proc_work);
break;
}
}
spin_unlock_irqrestore(&pidmap_lock, flags);

15
kernel/pid_namespace.c
View File

@ -217,22 +217,15 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns)
/*
* sys_wait4() above can't reap the TASK_DEAD children.
* Make sure they all go away, see __unhash_process().
* Make sure they all go away, see free_pid().
*/
for (;;) {
bool need_wait = false;
read_lock(&tasklist_lock);
if (!list_empty(&current->children)) {
__set_current_state(TASK_UNINTERRUPTIBLE);
need_wait = true;
}
read_unlock(&tasklist_lock);
if (!need_wait)
set_current_state(TASK_UNINTERRUPTIBLE);
if (pid_ns->nr_hashed == 1)
break;
schedule();
}
__set_current_state(TASK_RUNNING);
if (pid_ns->reboot)
current->signal->group_exit_code = pid_ns->reboot;