Messages in this thread | | | Date | Thu, 26 May 2011 17:01:50 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 03/10] ptrace: implement PTRACE_SEIZE |
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On 05/26, Tejun Heo wrote: > > Hello, > > On Wed, May 25, 2011 at 08:29:19PM +0200, Oleg Nesterov wrote: > > > > And. Currently there is no way to detach a zombie leader. Perhaps we > > > > should change do_wait(), but it is not clear what should we do if the > > > > tracer is the real parent (we already discussed this a bit). > > > > > > Hmmm... maybe just allow detaching zombie leader? > > > > Yes, I think we should do this. > > > > If we change PTRACE_DETACH (or add the new request) to allow this, then > > I think it it should detach any zombie, leader or not. > > I think we can just make PTRACE_DETACH to succeed for zombies. No > reason to add a new request for this.
OK.
> > Or we can change do_wait() to detach a zombie leader. In this case it > > is not clear what should we do if the debugger is the real parent. > > Perhaps do_wait() should do the same: detach a leader (but not reap). > > When the last thread does, the real parent will be notified again. > > IOW, wait(tgid) can succeed twice. > > Just letting PTRACE_DETACH work for zombies sounds much simpler to me.
Probably, but please note we have to modify do_wait() anyway. Otherwise in general the tracer simply can not know the tracee has exited. IOW, waitpid(zombie_leader_pid, WEXITED) should succeed without reaping if delay_group_leader(), then the tracer can do PTRACE_DETACH. But this is not symmetrical with sub-thread zombies.
Oleg.
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