From: Michal Hocko <mhocko@kernel.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
strace-devel@lists.sourceforge.net,
Mike Galbraith <umgwanakikbuti@gmail.com>,
Aleksa Sarai <asarai@suse.com>
Subject: Re: strace lockup when tracing exec in go
Date: Fri, 23 Sep 2016 13:18:09 +0200 [thread overview]
Message-ID: <20160923111808.GJ4478@dhcp22.suse.cz> (raw)
In-Reply-To: <20160923102141.GA16189@redhat.com>
On Fri 23-09-16 12:21:41, Oleg Nesterov wrote:
> On 09/22, Michal Hocko wrote:
> >
> > --- a/kernel/signal.c
> > +++ b/kernel/signal.c
> > @@ -91,6 +91,10 @@ static int sig_ignored(struct task_struct *t, int sig, bool force)
> > if (!sig_task_ignored(t, sig, force))
> > return 0;
> >
> > + /* Do not ignore signals sent from child to the parent */
> > + if (current->ptrace && current->parent == t)
> > + return 0;
>
> This doesn't look right in general, and this can't really help.
>
> This assumes that the tracer will call do_wait() after mm_access()
> fails, but this is not necessarily true.
>
> Note also ptrace_attach(), -ERESTARTNOINTR means that the tracer won't
> even return to user-space if SIGCHLD is ignored, the tracer will silently
> restart the syscall.
Well, it apparently does help the strace case. So I am not arguing this
is the best fix but can it be harmful?
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2016-09-23 11:18 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-21 15:29 strace lockup when tracing exec in go Michal Hocko
2016-09-22 4:15 ` Mike Galbraith
2016-09-22 8:01 ` Michal Hocko
2016-09-22 8:20 ` Aleksa Sarai
2016-09-22 8:36 ` Michal Hocko
2016-09-22 9:40 ` Mike Galbraith
2016-09-22 9:53 ` Michal Hocko
2016-09-22 10:09 ` Mike Galbraith
2016-09-22 11:09 ` Michal Hocko
2016-09-22 13:53 ` Michal Hocko
2016-09-23 1:17 ` Aleksa Sarai
2016-09-23 10:21 ` Oleg Nesterov
2016-09-23 11:18 ` Michal Hocko [this message]
2016-09-23 13:21 ` Oleg Nesterov
2016-09-23 13:40 ` Michal Hocko
2016-09-23 14:07 ` Oleg Nesterov
2016-09-23 14:19 ` Michal Hocko
2016-09-23 9:50 ` Oleg Nesterov
2016-09-23 11:23 ` Michal Hocko
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