Re: strace lockup when tracing exec in go

From: Michal Hocko
Date: Thu Sep 22 2016 - 09:53:23 EST

On Thu 22-09-16 13:09:25, Michal Hocko wrote:
> On Thu 22-09-16 12:09:05, Mike Galbraith wrote:
> > On Thu, 2016-09-22 at 11:53 +0200, Michal Hocko wrote:
> > > On Thu 22-09-16 11:40:09, Mike Galbraith wrote:
> >
> > > > This patch doesn't help, nor does the previous patch... but with both
> > > > applied, all is well. All you have to do now is figure out why :)
> > >
> > > Ohh, I should be more explicit, this needs the mm_access part as well.
> > > Sorry for not being clear enough. So the full change is
> >
> > Ah. That was gonna happen after lunch, but since you already know it
> > works, I can get back to un-b0rking one of my trees.
> Yeah, it should work. The testcase is running in a loop for more than
> hour already and everything seems to be ok. Now the question is whether
> the fix is really correct which is something for Oleg.
> Also I think there is at least one more issue lurking there. Without or
> without the patch I can make tracer get stuck in do_wait waiting for
> task which doesn't seem to be alive anymore. I will report it separately
> after this one gets resolved to not pull more confusion in.

OK, the test in the loop has survived 3h of runtime without a single
lockup so the patch seems to be working for this case. I am posting the
patch with the full changelog, let's see if it is correct as well. As
I've said earlier this might be a strace bug which does an unexpected
syscall while it should be doing wait on the child process instead.

If the patch is correct then I would mark it for stable as well.