linux-kernel - Re: 3.18 nohz + audit regression (Re: [PATCH] context_tracking: Restore previous state in schedule

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Message-ID: <20141204142301.GA3269@lerouge>
Date:	Thu, 4 Dec 2014 15:23:04 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Richard Guy Briggs <rgb@...hat.com>,
	Eric Paris <eparis@...hat.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: 3.18 nohz + audit regression (Re: [PATCH] context_tracking:
 Restore previous state in schedule_user)

On Wed, Dec 03, 2014 at 08:58:46PM -0800, Linus Torvalds wrote:
> On Wed, Dec 3, 2014 at 5:29 PM, Andy Lutomirski <luto@...capital.net> wrote:
> >
> > So, to summarize the choices for 3.18:
> >
> > 4. This patch.
> 
> I've applied it. The alternatives look worse, and the patch doesn't
> look bad. In many ways it looks better than the old user_exit/enter
> pair, although obviously the "schedule_user()" name is kind of odd
> now. Whatever.

That doesn't look like the safest approach to me. Somehow I felt more
comfortable with exception_enter/exit on the audit function.

A few other archs use schedule_user() as well, it's likely fine but I'm
not sure how subtle their path is.

Besides, is it possible that the audit function gets called after
syscall_trace_leave() or do_notify_resume()? If so, the patch won't fix
the issue entirely.
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