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From: Stephen Hemminger <stephen@networkplumber.org>
To: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Cc: dev@dpdk.org, ruifeng.wang@arm.com, feifei.wang@arm.com, nd@arm.com
Subject: Re: [dpdk-dev] [RFC 0/5] Use correct memory ordering in eal functions
Date: Mon, 1 Mar 2021 08:41:53 -0800	[thread overview]
Message-ID: <20210301084153.50b1c397@hermes.local> (raw)
In-Reply-To: <20210224212018.17576-1-honnappa.nagarahalli@arm.com>

On Wed, 24 Feb 2021 15:20:13 -0600
Honnappa Nagarahalli <honnappa.nagarahalli@arm.com> wrote:

> rte_eal_remote_launch and rte_eal_wait_lcore need to provide
> correct memory ordering to address the data communication from
> main core to worker core and vice versa.
> 
> There are 2 use cases:
> 1) All the store operations (meant for worker) by main core
> should be visible to worker core before the worker core runs the
> assigned function
> 
> 2) All the store operations by the worker core should be visible
> to the main core after rte_eal_wait_lcore returns.
> 
> For the data that needs to be communicated to the worker after
> the rte_eal_remote_launch returns, load-acquire and store-release
> semantics should be used (just like any other writer-reader use case).
> 
> For the main to worker communication, the pointer to function
> to execute is used as the guard variable. Hence, resetting of
> the function pointer is important.
> 
> For the worker to main communication, the existing code uses the
> lcore state as the guard variable. However, it looks like
> the FINISHED state is not really required. Hence the FINISHED state
> is removed before using the state as the guard variable. I would like
> some feedback on why the FINISHED state is required. I have not
> paid attention to what it means for backward compatibility.
> If it is decided to remove this state, documentation changes are
> required.
> 


Most likely all use of volatile in DPDK is suspect.
Perhaps we should re-enable the "volatile considered harmful" warning
in checkpatch

  parent reply	other threads:[~2021-03-01 16:42 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-24 21:20 Honnappa Nagarahalli
2021-02-24 21:20 ` [dpdk-dev] [RFC 1/5] eal: reset lcore function pointer and argument Honnappa Nagarahalli
2021-02-24 21:20 ` [dpdk-dev] [RFC 2/5] eal: ensure memory operations are visible to worker Honnappa Nagarahalli
2021-02-24 21:20 ` [dpdk-dev] [RFC 3/5] eal: lcore state FINISHED is not required Honnappa Nagarahalli
     [not found]   ` <AM5PR0802MB2465B62994239817E0AC46C59E9E9@AM5PR0802MB2465.eurprd08.prod.outlook.com>
2021-02-25  8:44     ` [dpdk-dev] 回复: " Feifei Wang
2021-02-25 23:33       ` [dpdk-dev] " Honnappa Nagarahalli
2021-02-26  8:26         ` Thomas Monjalon
2021-03-02  3:13           ` Honnappa Nagarahalli
2021-03-19 13:42             ` Ananyev, Konstantin
2021-03-30  2:54               ` Honnappa Nagarahalli
2021-03-01  5:55         ` [dpdk-dev] 回复: " Feifei Wang
2021-02-24 21:20 ` [dpdk-dev] [RFC 4/5] eal: ensure memory operations are visible to main Honnappa Nagarahalli
2021-02-24 21:20 ` [dpdk-dev] [RFC 5/5] test/ring: use relaxed barriers for ring stress test Honnappa Nagarahalli
2021-03-01 16:41 ` Stephen Hemminger [this message]
2021-03-02 16:06   ` [dpdk-dev] [RFC 0/5] Use correct memory ordering in eal functions Honnappa Nagarahalli
2021-09-09 23:13 ` [dpdk-dev] [PATCH v2 0/6] " Honnappa Nagarahalli
2021-09-09 23:13   ` [dpdk-dev] [PATCH v2 1/6] eal: reset lcore function pointer and argument Honnappa Nagarahalli
2021-09-10  7:49     ` Bruce Richardson
2021-09-10  8:12       ` David Marchand
2021-09-11 22:19         ` Honnappa Nagarahalli
2021-09-09 23:13   ` [dpdk-dev] [PATCH v2 2/6] eal: ensure memory operations are visible to worker Honnappa Nagarahalli
2021-09-09 23:13   ` [dpdk-dev] [PATCH v2 3/6] eal: lcore state FINISHED is not required Honnappa Nagarahalli
2021-09-09 23:13   ` [dpdk-dev] [PATCH v2 4/6] eal: update rte_eal_wait_lcore definition Honnappa Nagarahalli
2021-09-09 23:37     ` Honnappa Nagarahalli
2021-09-09 23:13   ` [dpdk-dev] [PATCH v2 5/6] eal: ensure memory operations are visible to main Honnappa Nagarahalli
2021-09-09 23:13   ` [dpdk-dev] [PATCH v2 6/6] test/ring: use relaxed barriers for ring stress test Honnappa Nagarahalli
2021-10-07 11:55     ` Ananyev, Konstantin
2021-10-07 23:40       ` Honnappa Nagarahalli
2021-10-25  4:52 ` [dpdk-dev] [PATCH v3 0/4] Use correct memory ordering in eal functions Honnappa Nagarahalli
2021-10-25  4:52   ` [dpdk-dev] [PATCH v3 1/4] eal: reset lcore function pointer and argument Honnappa Nagarahalli
2021-10-25  4:52   ` [dpdk-dev] [PATCH v3 2/4] eal: lcore state FINISHED is not required Honnappa Nagarahalli
2021-10-25  4:52   ` [dpdk-dev] [PATCH v3 3/4] eal: use correct memory ordering Honnappa Nagarahalli
2021-10-25  4:52   ` [dpdk-dev] [PATCH v3 4/4] test/ring: use relaxed barriers for ring stress test Honnappa Nagarahalli
2021-10-25 16:23   ` [dpdk-dev] [PATCH v3 0/4] Use correct memory ordering in eal functions David Marchand

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