linux-kernel - Re: [PATCH 06/12] x86/mm: Enable and use the arch_pgd_init

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Message-ID: <20150612225711.GB24699@redhat.com>
Date:	Sat, 13 Jun 2015 00:57:11 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	linux-kernel@...r.kernel.org, linux-mml@...r.kernel.org,
	Andy Lutomirski <luto@...capital.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Brian Gerst <brgerst@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Waiman Long <Waiman.Long@...com>
Subject: Re: [PATCH 06/12] x86/mm: Enable and use the arch_pgd_init_late()
	method

On 06/13, Oleg Nesterov wrote:
>
> Afaics, we need to ensure that:
>
> > +			if (pgd_val(*pgd_src))
> > +				WRITE_ONCE(*pgd_dst, *pgd_src);
>
> either we notice the recent update of this PGD, or (say) the subsequent
> sync_global_pgds() can miss the child.

and perhaps !pgd_none(pgd_src) will look better.

Oleg.

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