Re: strace lockup when tracing exec in go

From: Aleksa Sarai
Date: Thu Sep 22 2016 - 21:17:02 EST

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.

This patch fixes the test case, but it also fixes the original issue (that strace of runC would fail when the container init process is exec-ing the user init process). Thanks Michal, I'll apply it to my local kernel. :D

Aleksa Sarai
Software Engineer (Containers)
SUSE Linux GmbH