Messages in this thread | | | Date | Wed, 16 May 2012 20:39:20 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 2/3] pidns: Guarantee that the pidns init will be the last pidns process reaped. |
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Eric, sorry for the huge delay, I was on vacation when you sent this patch...
On 05/06, Eric W. Biederman wrote: > > @@ -798,6 +815,12 @@ static void forget_original_parent(struct task_struct *father) > exit_ptrace(father); > reaper = find_new_reaper(father); > > + /* Return immediately if we aren't going to reparent anything */ > + if (unlikely(reaper == father)) { > + write_unlock_irq(&tasklist_lock); > + return; > + }
I was confused by the comment. Afaics, it is not that "we aren't going to reparent", we need this change because we can't "reparent" to the same thread, list_for_each_entry_safe() below can never stop. But this is off-topic...
Hmm. I don't think the patch is 100% correct. Afaics, this needs more delay_pidns_leader() checks.
For example. Suppose we have a CLONE_NEWPID zombie I, it has an EXIT_DEAD child D so delay_pidns_leader(I) == T.
Now suppose that I->real_parent exits, lets denote this task as P.
Suppose that P->real_parent ignores SIGCHLD.
In this case P will do release_task(I) prematurely. And worse, when D finally does realease_task(D) it will do realease_task(I) again.
Oleg.
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