> So I've stared into do_notify_parent some more and the following was
> just very confusing
>       if (!tsk->ptrace && sig == SIGCHLD &&
>           (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN ||
>            (psig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT))) {
>               /*
>                * We are exiting and our parent doesn't care.  POSIX.1
>                * defines special semantics for setting SIGCHLD to SIG_IGN
>                * or setting the SA_NOCLDWAIT flag: we should be reaped
>                * automatically and not left for our parent's wait4 call.
>                * Rather than having the parent do it as a magic kind of
>                * signal handler, we just set this to tell do_exit that we
>                * can be cleaned up without becoming a zombie.  Note that
>                * we still call __wake_up_parent in this case, because a
>                * blocked sys_wait4 might now return -ECHILD.
>                *
>                * Whether we send SIGCHLD or not for SA_NOCLDWAIT
>                * is implementation-defined: we do (if you don't want
>                * it, just use SIG_IGN instead).
>                */
>               autoreap = true;
>               if (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN)
>                       sig = 0;
>       }
> it tries to prevent from what I am seeing in a way. If the SIGCHLD is
> ignored then it just does autoreap and everything is fine. But this
> doesn't seem to be the case here. In fact we are not sending the signal
> because sig_task_ignored is true resp. sig_handler_ignored which can
> fail even for handler == SIG_DFL && sig_kernel_ignore() and SIGCHLD
> seems to be in SIG_KERNEL_IGNORE_MASK. So I've tried

I was looking at the same code this morning. I thought maybe we should 
drop the !tsk->ptrace condition (or make it so that the condition still 
succeeds if the tracer also happens to be tsk->real_parent) -- since 
this is only happening when the process is being traced? I tried this 
and the issue still persists, but I didn't apply your other proposed 
change to this conditional.

Or am I misunderstanding what tsk->ptrace refers to?

Aleksa Sarai
Software Engineer (Containers)
SUSE Linux GmbH

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