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charset="us-ascii" Content-Transfer-Encoding: quoted-printable I assume this answer is No, but just wanted to be confirmed. Thanks, Changchun ________________________________ From: Changchun Zhang Sent: Monday, February 17, 2025 2:14 PM To: Stephen Hemminger Cc: Van Haaren, Harry ; NAGENDRA BALAGANI ; users@dpdk.org Subject: Re: [External] : Re: Query Regarding Race Condition Between Packet= Reception and Device Stop in DPDK Okay, so here the issue is still rte_eth_dev_stop(), but not rte_eth_dev_rx= _queue_stop(), right? I mean, as long as not calling rte_eth_dev_stop() on = control path, is it safe to call rte_eth_dev_rx_queue_stop/rte_eth_dev_rx_q= ueue_start on control path while fast path keeps calling rte_eth_rx_burst()= ? Thanks, Changchun ________________________________ From: Stephen Hemminger Sent: Monday, February 17, 2025 2:06 PM To: Changchun Zhang Cc: Van Haaren, Harry ; NAGENDRA BALAGANI ; users@dpdk.org Subject: Re: [External] : Re: Query Regarding Race Condition Between Packet= Reception and Device Stop in DPDK On Mon, 17 Feb 2025 18:57:00 +0000 Changchun Zhang wrote: > Hi Harry, > > Can we call rte_eth_dev_rx_queue_stop() on a rx queue when a fast path is= still polling the queue? The sequence on control and fast path cores would= like: > Control path: > rte_eth_dev_rx_queue_stop(rx_queue_id); > ...waiting for draining of rx_queue... > rte_eth_dev_stop() > .... > > Fast path: > Keep calling rte_eth_rx_burst() > (I am expecting it will return 0 if queue is already drained and stopped) > No. The application needs to not call rx_burst when stop is being done. There rx_burst is a fast path with no additional checks and is intentionall= y not thread safe. You need to coordinate queue management inside the application. --_000_CO1PR10MB475683581053E55C686B9B9384FB2CO1PR10MB4756namp_ Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable
I assume this answer is No, but just wanted to be confirmed. 


 

Thanks,

Changchun

 

From: Changchun Zhang <c= hangchun.zhang@oracle.com>
Sent: Monday, February 17, 2025 2:14 PM
To: Stephen Hemminger <stephen@networkplumber.org>
Cc: Van Haaren, Harry <harry.van.haaren@intel.com>; NAGENDRA B= ALAGANI <nagendra.balagani@oracle.com>; users@dpdk.org <users@dpdk= .org>
Subject: Re: [External] : Re: Query Regarding Race Condition Between= Packet Reception and Device Stop in DPDK
 
Okay, so here the issue is still rte_eth_dev_stop(), but not rte_eth_dev_rx= _queue_stop(), right? I mean, as long as not calling rte_eth_dev_stop() on = control path, is it safe to call rte_eth_dev_rx_queue_stop/rte_eth_dev_rx_q= ueue_start on control path while fast path keeps calling rte_eth_rx_burst()? 


 

Thanks,

Changchun

 


From: Stephen Hem= minger <stephen@networkplumber.org>
Sent: Monday, February 17, 2025 2:06 PM
To: Changchun Zhang <changchun.zhang@oracle.com>
Cc: Van Haaren, Harry <harry.van.haaren@intel.com>; NAGEN= DRA BALAGANI <nagendra.balagani@oracle.com>; users@dpdk.org <users= @dpdk.org>
Subject: Re: [External] : Re: Query Regarding Race Condition Be= tween Packet Reception and Device Stop in DPDK
 
On Mon, 17 Feb 202= 5 18:57:00 +0000
Changchun Zhang <changchun.zhang@oracle.com> wrote:

> Hi Harry,
>
> Can we call rte_eth_dev_rx_queue_stop() on a rx queue when a fast path= is still polling the queue? The sequence on control and fast path cores wo= uld like:
> Control path:
> rte_eth_dev_rx_queue_stop(rx_queue_id);
> ...waiting for draining of rx_queue...
> rte_eth_dev_stop()
> ....
>
> Fast path:
> Keep calling rte_eth_rx_burst()
> (I am expecting it will return 0 if queue is already drained and stopp= ed)
>

No.
The application needs to not call rx_burst when stop is being done.
There rx_burst is a fast path with no additional checks and is intentionall= y not thread safe.
You need to coordinate queue management inside the application.
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