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Re: ptrace group stop signal number not reset before PTRACE_INTERRUPT is delivered?

From Keno Fischer <keno@juliacomputing.com>
Newsgroups linux.kernel
Subject Re: ptrace group stop signal number not reset before PTRACE_INTERRUPT is delivered?
Date 2016-08-19 04:50 +0200
Message-ID <s7I2B-8cc-13@gated-at.bofh.it> (permalink)
References <s7mEN-2uu-5@gated-at.bofh.it> <s7wEa-10D-35@gated-at.bofh.it> <s7GtS-7go-117@gated-at.bofh.it> <s7HpU-7RC-17@gated-at.bofh.it>
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On Thu, Aug 18, 2016 at 12:23 PM, Oleg Nesterov <oleg@redhat.com> wrote:
>
> And you if you get PTRACE_EVENT_STOP and WSTOPSIG() == SIGTTIN after
> PTRACE_INTERRUPT, you know that the tracee did not report the "new"
> SIGTTIN.

It seems possible to remember whether or not we injected a stopping
signal and if so the next PTRACE_EVENT_STOP is a group-stop, otherwise
a PTRACE_INTERRUPT stop. Currently what I do is the other way around,
after issuing PTRACE_INTERRUPT, the first (if any) of the next two
stops that is a PTRACE_EVENT_STOP get interpreted as a
PTRACE_INTERRUPT stop. I haven't thought through this fully yet, so I
can't give you a concrete example I worried about, it just seems
fragile compared to just checking whether WSTOPSIG() == SIGTRAP.

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Thread

ptrace group stop signal number not reset before PTRACE_INTERRUPT is delivered? Keno Fischer <keno@juliacomputing.com> - 2016-08-18 06:00 +0200
  Re: ptrace group stop signal number not reset before  PTRACE_INTERRUPT is delivered? Oleg Nesterov <oleg@redhat.com> - 2016-08-18 16:40 +0200
    Re: ptrace group stop signal number not reset before         PTRACE_INTERRUPT is delivered? Oleg Nesterov <oleg@redhat.com> - 2016-08-19 03:10 +0200
      Re: ptrace group stop signal number not reset before         PTRACE_INTERRUPT is delivered? Oleg Nesterov <oleg@redhat.com> - 2016-08-19 04:10 +0200
        Re: ptrace group stop signal number not reset before PTRACE_INTERRUPT  is delivered? Keno Fischer <keno@juliacomputing.com> - 2016-08-19 04:50 +0200
          Re: ptrace group stop signal number not reset before         PTRACE_INTERRUPT is delivered? Oleg Nesterov <oleg@redhat.com> - 2016-08-23 17:40 +0200

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