linux-kernel - Re: [PATCH RESEND 2/2] tracing: syscall_regfunc() should not skip kernel threads

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Message-ID: <20140410133855.GC12228@redhat.com>
Date:	Thu, 10 Apr 2014 15:38:55 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH RESEND 2/2] tracing: syscall_regfunc() should not skip
	kernel threads

On 04/10, Steven Rostedt wrote:
>
> On Wed, 9 Apr 2014 19:06:16 +0200
> Oleg Nesterov <oleg@...hat.com> wrote:
>
> > syscall_regfunc() ignores the kernel thread because "it has
> > no effect", see cc3b13c1 "Don't trace kernel thread syscalls".
> >
> > However, this means that a user-space task spawned by
> > call_usermodehelper() won't report the system calls if
> > kernel_execve() is called when sys_tracepoint_refcount != 0.
>
> What about doing the set there? That is, we could add a check in the
> call_userspacehelper() just before it does the do_execve, that if
> sys_tracepoint_refcount is set, we set the TIF flag.

But for what?

And if we do this, ____call_usermodehelper() needs write_lock_irq(tasklist)
to serialize with syscall_*regfunc().

Oleg.

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