linux-kernel - Re: x86: get rid of the insane TIF_ABI

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Message-ID: <20100216101903.GA1057@redhat.com>
Date:	Tue, 16 Feb 2010 11:19:03 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andi Kleen <andi@...stfloor.org>, "H. Peter Anvin" <hpa@...or.com>
Cc:	Roland McGrath <roland@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: x86: get rid of the insane TIF_ABI_PENDING bit

On 02/15, H. Peter Anvin wrote:
>
> On 02/15/2010 11:41 AM, Roland McGrath wrote:
> > It affects whatever uses is_compat_task(), but I can't see anything
> > where that matters except inside some particular syscall or for
> > syscall restart after signals.
>
> FWIW, the origin of this is checkin
> 4d9bc79cd28b779610d9590b3a96a28a0f64a25a (2.6.18-rc1), which somewhat
> unhelpfully states "Make sure is_compat_task works early".  It doesn't
> specify what the failure is if is_compat_task doesn't work early.

Perhaps Andi could explain us why this is needed,

> On
> the other hand, it sure as heck seems better to set it and not need it
> than the other way around.

Agreed, but otoh it is always good to understand the code. If we
really have a reason for TS_COMPAT, a small comment can help other
readers.

Oleg.

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