linux-kernel - Re: [PATCH RESEND 1/2] tracing: syscall_*regfunc() can race with copy

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Message-ID: <20140410090452.6b7677fc@gandalf.local.home>
Date:	Thu, 10 Apr 2014 09:04:52 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Oleg Nesterov <oleg@...hat.com>
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 1/2] tracing: syscall_*regfunc() can race with
 copy_process()

On Wed, 9 Apr 2014 19:05:42 +0200
Oleg Nesterov <oleg@...hat.com> wrote:

> syscall_regfunc() and syscall_unregfunc() should set/clear
> TIF_SYSCALL_TRACEPOINT system-wide, but do_each_thread() can race
> with copy_process() and miss the new child which was not added to
> init_task.tasks list yet.
> 
> Change copy_process() to update the child's TIF_SYSCALL_TRACEPOINT
> under tasklist.
> 
> While at it,
> 
> 	- remove _irqsafe from syscall_regfunc/syscall_unregfunc,
> 	  read_lock(tasklist) doesn't need to disable irqs.
> 
> 	- change syscall_unregfunc() to check PF_KTHREAD to skip
> 	  the kernel threads, ->mm != NULL is the common mistake.
> 
> 	  Note: probably this check should be simply removed, needs
> 	  another patch.
> 
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>

BTW, how important is this fix? Something we should aim for the current
merge window? stable? Or can it wait till 3.16?

-- Steve
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