[PATCH 2/2] ethdev: fix race condition in fast-path ops setup
Stephen Hemminger
stephen at networkplumber.org
Tue Feb 21 18:00:53 CET 2023
On Tue, 21 Feb 2023 07:24:19 +0000
Ruifeng Wang <Ruifeng.Wang at arm.com> wrote:
> > -----Original Message-----
> > From: fengchengwen <fengchengwen at huawei.com>
> > Sent: Monday, February 20, 2023 2:58 PM
> > To: Ashok Kaladi <ashok.k.kaladi at intel.com>; jerinj at marvell.com; thomas at monjalon.net
> > Cc: dev at dpdk.org; s.v.naga.harish.k at intel.com; erik.g.carrillo at intel.com;
> > abhinandan.gujjar at intel.com; stable at dpdk.org; Ruifeng Wang <Ruifeng.Wang at arm.com>
> > Subject: Re: [PATCH 2/2] ethdev: fix race condition in fast-path ops setup
> >
> > On 2023/2/20 14:08, Ashok Kaladi wrote:
> > > If ethdev enqueue or dequeue function is called during
> > > eth_dev_fp_ops_setup(), it may get pre-empted after setting the
> > > function pointers, but before setting the pointer to port data.
> > > In this case the newly registered enqueue/dequeue function will use
> > > dummy port data and end up in seg fault.
> > >
> > > This patch moves the updation of each data pointers before updating
> > > corresponding function pointers.
> > >
> > > Fixes: c87d435a4d79 ("ethdev: copy fast-path API into separate
> > > structure")
> > > Cc: stable at dpdk.org
Why is something calling enqueue/dequeue when device is not fully started.
A correctly written application would not call rx/tx burst until after
ethdev start had finished.
Would something like this work better?
Note: there is another bug in current code. The check for link state interrupt
and link_ops could return -ENOTSUP and leave device in indeterminate state.
The check should be done before calling PMD.
diff --git a/lib/ethdev/rte_ethdev.c b/lib/ethdev/rte_ethdev.c
index 0266cc82acb6..d6c163ed85e7 100644
--- a/lib/ethdev/rte_ethdev.c
+++ b/lib/ethdev/rte_ethdev.c
@@ -1582,6 +1582,14 @@ rte_eth_dev_start(uint16_t port_id)
return 0;
}
+ if (dev->data->dev_conf.intr_conf.lsc == 0 &&
+ dev->dev_ops->link_update == NULL) {
+ RTE_ETHDEV_LOG(INFO,
+ "Device with port_id=%"PRIu16" link update not supported\n",
+ port_id);
+ return -ENOTSUP;
+ }
+
ret = rte_eth_dev_info_get(port_id, &dev_info);
if (ret != 0)
return ret;
@@ -1591,9 +1599,7 @@ rte_eth_dev_start(uint16_t port_id)
eth_dev_mac_restore(dev, &dev_info);
diag = (*dev->dev_ops->dev_start)(dev);
- if (diag == 0)
- dev->data->dev_started = 1;
- else
+ if (diag != 0)
return eth_err(port_id, diag);
ret = eth_dev_config_restore(dev, &dev_info, port_id);
@@ -1611,16 +1617,18 @@ rte_eth_dev_start(uint16_t port_id)
return ret;
}
- if (dev->data->dev_conf.intr_conf.lsc == 0) {
- if (*dev->dev_ops->link_update == NULL)
- return -ENOTSUP;
- (*dev->dev_ops->link_update)(dev, 0);
- }
-
/* expose selection of PMD fast-path functions */
eth_dev_fp_ops_setup(rte_eth_fp_ops + port_id, dev);
+ /* ensure state is set before marking device ready */
+ rte_smp_wmb();
+
rte_ethdev_trace_start(port_id);
+
+ /* Update current link state */
+ if (dev->data->dev_conf.intr_conf.lsc == 0)
+ (*dev->dev_ops->link_update)(dev, 0);
+
return 0;
}
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