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Date: Thu, 10 Apr 2014 15:55:54 -0400
From: Steven Rostedt <rostedt@goodmis.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
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        Ingo Molnar <mingo@kernel.org>,
        Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Subject: Re: [PATCH RESEND 2/2] tracing: syscall_regfunc() should not skip
 kernel threads
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On Thu, 10 Apr 2014 21:38:20 +0200
Oleg Nesterov <oleg@redhat.com> wrote:

> I _think_ that the kernel thread can only return from "call *%rbx" if
> it is no longer a kernel thread, iow, do_execve() was called.

Ah right. But only in special cases.

Actually, it only returns if the function in kernel_thread() returns,
and in the case of ____call_usermodehelper, it does an exec and
returns on success. But if it fails, it needs to call do_exit().

Thus, it's not sufficient to just say "only if do_execve is called" but
to say, if the handler that is called is only allowed to return iff it
did a execve first and succeeded.

-- Steve