From: "Richardson, Bruce" <bruce.richardson@intel.com>
To: David Marchand <david.marchand@6wind.com>, "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH 1/2] mem: add write memory barrier before changing heap state
Date: Tue, 15 Apr 2014 14:08:17 +0000 [thread overview]
Message-ID: <59AF69C657FD0841A61C55336867B5B01A9FCCFF@IRSMSX103.ger.corp.intel.com> (raw)
In-Reply-To: <1397569859-14460-1-git-send-email-david.marchand@6wind.com>
> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of David Marchand
> Sent: Tuesday, April 15, 2014 2:51 PM
> To: dev@dpdk.org
> Subject: [dpdk-dev] [PATCH 1/2] mem: add write memory barrier before
> changing heap state
>
> From: Didier Pallard <didier.pallard@6wind.com>
>
> a write memory barrier is needed before changing heap state value, else some
> concurrent core may see state changing before all initialization values are
> written to memory, causing unpredictable results in malloc function.
>
> Signed-off-by: Didier Pallard <didier.pallard@6wind.com>
No barrier should be necessary here. As in a number of other places, such as rings, compiler barriers can be used in place of write memory barriers, due to IA ordering rules. However, in this case, both variables referenced are volatile variables and so the assignments to them cannot be reordered by the compiler so no compiler barrier is necessary either.
Regards,
/Bruce
next prev parent reply other threads:[~2014-04-15 14:09 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-15 13:50 David Marchand
2014-04-15 13:50 ` [dpdk-dev] [PATCH 2/2] mem: fix initialization check for malloc heap David Marchand
2014-04-15 14:08 ` Richardson, Bruce [this message]
2014-04-16 8:55 ` [dpdk-dev] [PATCH 1/2] mem: add write memory barrier before changing heap state didier.pallard
2014-04-15 14:44 ` Neil Horman
2014-04-18 12:56 ` [dpdk-dev] [PATCH 0/2] rework heap initialisation David Marchand
2014-04-18 12:56 ` [dpdk-dev] [PATCH 1/2] malloc: get rid of numa_socket field David Marchand
2014-04-18 13:08 ` Neil Horman
2014-04-30 9:46 ` Thomas Monjalon
2014-04-18 12:56 ` [dpdk-dev] [PATCH 2/2] malloc: simplify heap initialisation David Marchand
2014-04-18 13:09 ` Neil Horman
2014-04-30 9:47 ` Thomas Monjalon
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