From: Andrew Rybchenko <arybchenko@solarflare.com>
To: Stephen Hemminger <stephen@networkplumber.org>
Cc: <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH v2 02/15] ethdev: add linkstatus get/set helper functions
Date: Sat, 6 Jan 2018 17:35:06 +0300 [thread overview]
Message-ID: <750b9eff-9ba0-60b3-e587-fb22c2bfc5b7@solarflare.com> (raw)
In-Reply-To: <20180106062456.1d1eba50@xeon-e3>
On 01/06/2018 05:24 PM, Stephen Hemminger wrote:
> On Sat, 6 Jan 2018 13:49:50 +0300
> Andrew Rybchenko <arybchenko@solarflare.com> wrote:
>
>> On 01/06/2018 04:06 AM, Stephen Hemminger wrote:
>>> +}
>>> +
>>> +void
>>> +_rte_eth_linkstatus_get(const struct rte_eth_dev *dev,
>>> + struct rte_eth_link *link)
>>> +{
>>> + const uint64_t *src = (const uint64_t *)&(dev->data->dev_link);
>>> + volatile uint64_t *dst = (uint64_t *)link;
>>> +
>>> + RTE_BUILD_BUG_ON(sizeof(*link) != sizeof(uint64_t));
>>> +
>>> + /*
>>> + * Note: this should never fail since both destination and expected
>>> + * values are the same and are a pointer from caller.
>>> + */
>>> + rte_atomic64_cmpset(dst, *dst, *src);
>> As I understand nobody says that *link (i.e. *dst) is initialized, so it
>> could be
>> reading uninitialized value. Not fatal, but not good as well.
>> May be it is better to use something like rte_atomic64_read().
>>
> link is a pointer passed in by the caller.
> If it is uninitialized, that is still ok since it will have some value.
I thought about valgrind. Yes, it is problematic to run with hugepages,
but should be possible (with some patches). If so, it will/can complain
about usage of uninitialized value.
> The different question is that since is almost backwards use of cmpset,
> not sure if processor really guarantees atomic read of source pointer.
> But this code is cloned from original in Intel driver so it is bug
> for bug compatiable!
I see, but if so it was local to corresponding Intel driver. Now it is
becoming global.
next prev parent reply other threads:[~2018-01-06 14:35 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-06 1:06 [dpdk-dev] [PATCH v2 00/15] common ethdev linkstatus functions Stephen Hemminger
2018-01-06 1:06 ` [dpdk-dev] [PATCH v2 01/15] eal: introduce atomic exchange operation Stephen Hemminger
2018-01-06 1:06 ` [dpdk-dev] [PATCH v2 02/15] ethdev: add linkstatus get/set helper functions Stephen Hemminger
2018-01-06 10:49 ` Andrew Rybchenko
2018-01-06 14:24 ` Stephen Hemminger
2018-01-06 14:35 ` Andrew Rybchenko [this message]
2018-01-06 1:06 ` [dpdk-dev] [PATCH v2 03/15] virtio: use eth_linkstatus_set Stephen Hemminger
2018-01-06 3:10 ` Tiwei Bie
2018-01-08 17:03 ` Stephen Hemminger
2018-01-06 1:06 ` [dpdk-dev] [PATCH v2 04/15] vmxnet3: use rte_eth_linkstatus_set Stephen Hemminger
2018-01-06 1:06 ` [dpdk-dev] [PATCH v2 05/15] dpaa2: " Stephen Hemminger
2018-01-06 1:06 ` [dpdk-dev] [PATCH v2 06/15] nfp: use rte_eth_linkstatus functions Stephen Hemminger
2018-01-06 1:06 ` [dpdk-dev] [PATCH v2 07/15] e1000: use rte_eth_linkstatus helpers Stephen Hemminger
2018-01-06 1:06 ` [dpdk-dev] [PATCH v2 08/15] ixgbe: use rte_eth_linkstatus functions Stephen Hemminger
2018-01-06 1:06 ` [dpdk-dev] [PATCH v2 09/15] sfc: use new " Stephen Hemminger
2018-01-06 11:10 ` Andrew Rybchenko
2018-01-06 1:06 ` [dpdk-dev] [PATCH v2 10/15] i40e: use " Stephen Hemminger
2018-01-06 1:06 ` [dpdk-dev] [PATCH v2 11/15] liquidio: use _rte_eth_linkstatus_set Stephen Hemminger
2018-01-06 1:06 ` [dpdk-dev] [PATCH v2 12/15] thunderx: " Stephen Hemminger
2018-01-06 1:06 ` [dpdk-dev] [PATCH v2 13/15] szedata: " Stephen Hemminger
2018-01-06 1:06 ` [dpdk-dev] [PATCH v2 14/15] octeontx: use rte_eth_linkstatus_set Stephen Hemminger
2018-01-06 1:06 ` [dpdk-dev] [PATCH v2 15/15] enic: use _rte_eth_linkstatus_set Stephen Hemminger
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