linux-kernel - Re: [PATCH RFC 2/4] x86/arch_prctl: add ARCH_GET_NOPTI and ARCH_SET

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Date:   Mon, 8 Jan 2018 17:56:51 +0100
From:   Willy Tarreau <w@....eu>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org, tglx@...utronix.de,
        gnomes@...rguk.ukuu.org.uk, torvalds@...ux-foundation.org
Subject: Re: [PATCH RFC 2/4] x86/arch_prctl: add ARCH_GET_NOPTI and
 ARCH_SET_NOPTI to enable/disable PTI

On Mon, Jan 08, 2018 at 05:49:00PM +0100, Peter Zijlstra wrote:
> On Mon, Jan 08, 2018 at 05:12:17PM +0100, Willy Tarreau wrote:
> > +		if (doit) {
> > +			if (arg2)
> > +				task_thread_info(task)->flags |= _TIF_NOPTI;
> > +			else
> > +				task_thread_info(task)->flags &= ~_TIF_NOPTI;
> 
> {set,clear}_thread_flag() please, the above is not SMP safe.

Oops, thank you. I initially thought about it initially but didn't
know the names of the functions to use, and have left it there
thinking I'd fix it later. Usual source of bugs :-/

Bah and I left my debugging printk() in the patch as well! I'll
rework this a bit.

Thanks,
Willy