linux-kernel - Re: [PATCH 1/1] powerpc/mm: Add memory barrier in __hugepte

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Message-ID: <20160406095623.GA24283@dhcp22.suse.cz>
Date:	Wed, 6 Apr 2016 11:56:24 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
Cc:	Michael Ellerman <mpe@...erman.id.au>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linuxppc-dev@...ts.ozlabs.org, James Dykman <jdykman@...ibm.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Subject: Re: [PATCH 1/1] powerpc/mm: Add memory barrier in __hugepte_alloc()

On Tue 05-04-16 12:05:47, Sukadev Bhattiprolu wrote:
[...]
> diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
> index d991b9e..081f679 100644
> --- a/arch/powerpc/mm/hugetlbpage.c
> +++ b/arch/powerpc/mm/hugetlbpage.c
> @@ -81,6 +81,13 @@ static int __hugepte_alloc(struct mm_struct *mm, hugepd_t *hpdp,
>  	if (! new)
>  		return -ENOMEM;
>  
> +	/*
> +	 * Make sure other cpus find the hugepd set only after a
> +	 * properly initialized page table is visible to them.
> +	 * For more details look for comment in __pte_alloc().
> +	 */
> +	smp_wmb();
> +

what is the pairing memory barrier?

>  	spin_lock(&mm->page_table_lock);
>  #ifdef CONFIG_PPC_FSL_BOOK3E
>  	/*
> -- 
> 1.8.3.1

-- 
Michal Hocko
SUSE Labs