From: Bing Zhao <bingz@nvidia.com>
To: <thomas@monjalon.net>, <ferruh.yigit@intel.com>,
<andrew.rybchenko@oktetlabs.ru>
Cc: <dev@dpdk.org>, <konstantin.ananyev@intel.com>
Subject: [dpdk-dev] [PATCH 2/2] ethdev: fix the race condition for fp ops reset
Date: Sat, 23 Oct 2021 00:14:07 +0300 [thread overview]
Message-ID: <20211022211407.315068-2-bingz@nvidia.com> (raw)
In-Reply-To: <20211022211407.315068-1-bingz@nvidia.com>
In the function "eth_dev_fp_ops_reset", a structure assignment
operation is used to reset one queue's callback functions, etc., but
it is not thread safe.
The structure assignment is not atomic, a lot of instructions will
be generated. Right now, since not all the fields are needed, the
fields in the "dummy_ops" which is not set explicitly will be 0s
based on the specification and compiler behavior. In order to make
"fpo" has the same content with "dummy_ops", some clearing to 0
operation is needed.
By checking the object instructions (e.g. with GCC 4.8.5)
0x0000000000a58317 <+35>: mov %rsi,%rdi
0x0000000000a5831a <+38>: mov %rdx,%rcx
=> 0x0000000000a5831d <+41>: rep stos %rax,%es:(%rdi)
0x0000000000a58320 <+44>: mov -0x38(%rsp),%rax
0x0000000000a58325 <+49>: lea -0xe0(%rip),%rdx
// # 0xa5824c <dummy_eth_rx_burst>
It shows that "rep stos" will clear the "fpo" structure before
assigning new values.
In the other thread, if some data path Tx / Rx functions are still
running, there is a risk to get 0 instead of the correct dummy
content.
1. qd = p->rxq.data[queue_id]
2. (void **)&p->rxq.clbk[queue_id]
"data" and "clbk" may be observed with NULL (0) in other threads.
Even it is temporary, the accessing to a NULL pointer will cause a
crash. Using "memcpy" could get rid of this.
Fixes: c87d435a4d79 ("ethdev: copy fast-path API into separate structure")
Cc: konstantin.ananyev@intel.com
Signed-off-by: Bing Zhao <bingz@nvidia.com>
---
lib/ethdev/ethdev_private.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/lib/ethdev/ethdev_private.c b/lib/ethdev/ethdev_private.c
index fbc3df91ad..cda9a6e228 100644
--- a/lib/ethdev/ethdev_private.c
+++ b/lib/ethdev/ethdev_private.c
@@ -206,7 +206,7 @@ eth_dev_fp_ops_reset(struct rte_eth_fp_ops *fpo)
.txq = {.data = dummy_data, .clbk = dummy_data,},
};
- *fpo = dummy_ops;
+ rte_memcpy(fpo, &dummy_ops, sizeof(struct rte_eth_fp_ops));
}
void
--
2.27.0
next prev parent reply other threads:[~2021-10-22 21:14 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-22 21:14 [dpdk-dev] [PATCH 1/2] ethdev: fix log level of Tx and Rx dummy functions Bing Zhao
2021-10-22 21:14 ` Bing Zhao [this message]
2021-10-23 8:34 ` [dpdk-dev] [PATCH 2/2] ethdev: fix the race condition for fp ops reset Thomas Monjalon
2021-10-23 11:39 ` Ananyev, Konstantin
2021-11-10 14:34 ` Ferruh Yigit
2021-11-10 14:37 ` Ananyev, Konstantin
2021-11-10 14:57 ` Thomas Monjalon
2021-11-10 15:24 ` Bing Zhao
2021-10-23 16:13 ` [dpdk-dev] " Stephen Hemminger
2021-10-24 5:54 ` Bing Zhao
2021-10-23 8:32 ` [dpdk-dev] [PATCH 1/2] ethdev: fix log level of Tx and Rx dummy functions Thomas Monjalon
2021-10-23 11:46 ` Ananyev, Konstantin
2021-10-23 12:45 ` Bing Zhao
2021-10-24 11:48 ` Ananyev, Konstantin
2021-10-25 9:43 ` Thomas Monjalon
2021-10-25 9:51 ` David Marchand
2021-10-25 12:55 ` Ananyev, Konstantin
2021-10-25 13:27 ` Thomas Monjalon
2021-10-25 13:31 ` David Marchand
2021-10-25 20:29 ` Ananyev, Konstantin
2021-10-25 20:38 ` Thomas Monjalon
2021-10-26 12:38 ` Ananyev, Konstantin
2021-10-26 12:59 ` Thomas Monjalon
2021-10-26 3:18 ` Bing Zhao
2021-10-23 12:12 ` Bing Zhao
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