From: "Morten Brørup" <mb@smartsharesystems.com>
To: "fengchengwen" <fengchengwen@huawei.com>
Cc: <dev@dpdk.org>, <huangdengdui@huawei.com>,
<stephen@networkplumber.org>, <roretzla@linux.microsoft.com>,
<thomas@monjalon.net>, <ferruh.yigit@amd.com>
Subject: RE: [PATCH v3] ethdev: fix strict aliasing lead to link cannot be up
Date: Fri, 12 Apr 2024 09:24:23 +0200 [thread overview]
Message-ID: <98CBD80474FA8B44BF855DF32C47DC35E9F39C@smartserver.smartshare.dk> (raw)
In-Reply-To: <653bfb6f-7a4e-b43d-be2f-b49ddf1cd667@huawei.com>
> From: fengchengwen [mailto:fengchengwen@huawei.com]
> Sent: Friday, 12 April 2024 05.28
[...]
> >> @@ -1701,12 +1696,8 @@ static inline void
> >> rte_eth_linkstatus_get(const struct rte_eth_dev *dev,
> >> struct rte_eth_link *link)
> >> {
> >> - RTE_ATOMIC(uint64_t) *src = (uint64_t __rte_atomic *)&(dev->data-
> >>> dev_link);
> >> - uint64_t *dst = (uint64_t *)link;
> >> -
> >> - RTE_BUILD_BUG_ON(sizeof(*link) != sizeof(uint64_t));
> >> -
> >> - *dst = rte_atomic_load_explicit(src, rte_memory_order_seq_cst);
> >> + link->val64 = rte_atomic_load_explicit(&dev->data->dev_link.val64,
> >> + rte_memory_order_seq_cst);
> >
> > It is not safe to assume that the link pointer points to local memory
> on the caller's stack.
> > The link pointer might point to a shared memory area, used by multiple
> threads/processes, so it needs to be stored atomically using
> rte_atomic_store_explicit(&link->val64, ..., rte_memory_order_seq_cst).
>
> I checked every call of rte_eth_linkstatus_get in DPDK, and all the link
> parameters are local variables.
> The dev->data->dev_link is placed in shared memory which could access
> from different threads/processes, it seems no need maintain another link
> struct which act the same role.
>
> So I think we should keep current impl, and not using
> rte_atomic_store_explicit(&link->val64,...
The application may pass a pointer to shared memory to the public rte_eth_link_get() function, which passes the pointer on to rte_eth_linkstatus_get():
https://elixir.bootlin.com/dpdk/v24.03/source/lib/ethdev/rte_ethdev.c#L2986
next prev parent reply other threads:[~2024-04-12 7:24 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-11 3:07 [PATCH] " Chengwen Feng
2024-04-11 6:53 ` Morten Brørup
2024-04-11 6:58 ` Morten Brørup
2024-04-11 11:57 ` fengchengwen
2024-04-11 12:44 ` Morten Brørup
2024-04-11 12:04 ` [PATCH v3] " Chengwen Feng
2024-04-11 12:44 ` Morten Brørup
2024-04-12 3:27 ` fengchengwen
2024-04-12 7:24 ` Morten Brørup [this message]
2024-04-11 15:05 ` [PATCH] " Stephen Hemminger
2024-04-12 8:16 ` fengchengwen
2024-04-12 8:49 ` [PATCH v4] " Chengwen Feng
2024-04-13 8:04 ` [PATCH v5] " Chengwen Feng
2024-04-13 8:48 ` [PATCH v6] " Chengwen Feng
2024-04-15 13:15 ` Morten Brørup
2024-04-18 7:28 ` [PATCH v7] " Chengwen Feng
2024-04-19 15:15 ` Ferruh Yigit
2024-04-19 15:25 ` Ferruh Yigit
2024-04-22 6:42 ` fengchengwen
2024-04-22 6:38 ` [PATCH v8] " Chengwen Feng
2024-04-22 10:54 ` Ferruh Yigit
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