Date: Sat, 13 Jun 2015 00:57:11 +0200
From: Oleg Nesterov <oleg@redhat.com>
To: Ingo Molnar <mingo@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-mml@vger.kernel.org,
        Andy Lutomirski <luto@amacapital.net>,
        Andrew Morton <akpm@linux-foundation.org>,
        Denys Vlasenko <dvlasenk@redhat.com>, Brian Gerst <brgerst@gmail.com>,
        Peter Zijlstra <peterz@infradead.org>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>, Waiman Long <Waiman.Long@hp.com>
Subject: Re: [PATCH 06/12] x86/mm: Enable and use the arch_pgd_init_late()
	method
Message-ID: <20150612225711.GB24699@redhat.com>
References: <1434031637-9091-1-git-send-email-mingo@kernel.org> <1434031637-9091-7-git-send-email-mingo@kernel.org> <20150612225000.GA24699@redhat.com>
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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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