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Date: Wed, 30 May 2012 20:15:15 +0200 From: Oleg Nesterov <oleg@...hat.com> To: Andrew Morton <akpm@...ux-foundation.org> Cc: Cyrill Gorcunov <gorcunov@...nvz.org>, "Eric W. Biederman" <ebiederm@...ssion.com>, Louis Rilling <louis.rilling@...labs.com>, Mike Galbraith <efault@....de>, Pavel Emelyanov <xemul@...allels.com>, linux-kernel@...r.kernel.org Subject: [PATCH 2/2] 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@...hat.com> Acked-by: "Eric W. Biederman" <ebiederm@...ssion.com> --- kernel/exit.c | 10 ++-------- 1 files changed, 2 insertions(+), 8 deletions(-) diff --git a/kernel/exit.c b/kernel/exit.c index 4fd4c55..ab972a7 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); } @@ -731,12 +731,6 @@ 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; -- 1.5.5.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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