From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oleg Nesterov Subject: Re: [PATCH] ptrace.2: Clarify PTRACE_INTERRUPT, PTRACE_LISTEN and group-stop behavior Date: Thu, 20 Jun 2013 16:24:52 +0200 Message-ID: <20130620142452.GA846@redhat.com> References: <1371726704-23409-1-git-send-email-dvlasenk@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1371726704-23409-1-git-send-email-dvlasenk-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> Sender: linux-man-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Denys Vlasenko Cc: Michael Kerrisk , Jan Kratochvil , "Dmitry V. Levin" , linux-man-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-man@vger.kernel.org On 06/20, Denys Vlasenko wrote: > > From: root I'll remove this guy from cc list before I reply ;) > For easier review, here are the changes as plain text: And thanks for the plain text. Looks good to me. A couple of nits. > PTRACE_INTERRUPT (since Linux 3.4) > Stop a tracee. > [*MODIFIED TEXT->**] If the tracee is running in kernel space > and PTRACE_SYSCALL is in effect, it will stop with syscall-exit-stop. Yes, but this looks a bit confusing. Or perhaps it is just me. IOW, it looks as if PTRACE_INTERRUPT has no effect in this case, the tracee should report syscall-exit anyway. I do not know how to explain this better... Perhaps. PTRACE_INTERRUPT sends the "fake" signal to the tracee (iow, it sets TIF_SIGPENDING and wakes it up). The tracee will report PTRACE_EVENT_STOP unless it is going to report something else (syscall, signal). I think it makes sense to mention that a) PTRACE_INTERRUPT is only valid if PTRACE_SEIZE was used, and b) this is the only request which doesn't need the stopped tracee. (PTRACE_KILL should die) > If any other ptrace-stop is generated at the same time > (for example, if a signal is sent to the tracee), this ptrace-stop > happens. Yes. Strictly speaking, do_jobctl_trap() is called before ptrace_signal(), so this depends on the timing. So I think this falls into "unless it is going to report something else" above. Denys, thanks a lot for this work! Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html