From: "Gaëtan Rivet" <gaetan.rivet@6wind.com>
To: Matan Azrad <matan@mellanox.com>
Cc: dev@dpdk.org, stable@dpdk.org
Subject: Re: [dpdk-dev] [PATCH] net/failsafe: fix Rx clean race
Date: Thu, 26 Oct 2017 18:20:29 +0200 [thread overview]
Message-ID: <20171026162029.GC10890@bidouze.vm.6wind.com> (raw)
In-Reply-To: <1508651468-31866-1-git-send-email-matan@mellanox.com>
Hello Matan,
I think the commit log could be shorter.
Proposing this, feel free to expand it if you prefer.
---8<---
When removing a device, the fail-safe checks that it is not within its
datapath before cleaning it.
When checking whether an Rx burst should be performed on a device, the
remove flag is not checked. Thus the port could still enter its datapath
and miss a removal round. Furthermore, there is a race between the
thread removing the device and the polling thread.
Check the remove flag before entering a sub-device Rx burst when in safe
mode. This check mitigates the aforementioned race condition.
--->8---
Otherwise,
On Sun, Oct 22, 2017 at 05:51:08AM +0000, Matan Azrad wrote:
> In case of plug out, the RMV interrupt callback sets the remove flag of
> the removed sub-device. The next hotplug alarm cycle should read this
> flag and if the data path are clean it should remove the sub-device.
>
> In case of fail-safe RX burst calling from application, fail-afe tries
> to call to all STARTED sub-device rx_burst functions. The remove flag
> is not checked here and fail-safe may call to the removed sub-device
> rx_burst function.
>
> The above 2 cases run in different threads and there is a race between
> the removed sub-device RX clean check to the removed sub-device
> rx_burst call makes the sub device RX unclean.
>
> If the application calls to rx_burst in loop, the probability to get RX
> clean is not enough, especially when there are few sub-devices or if the
> rx_burst function of the removed sub-device takes a lot of time.
>
> Each time the sub-device data path is unclean, the second oportunity to
> check it again should be only in the hotplug alarm next cycle; the
> default time between cycles is 2 seconds.
>
> In this loop when fail-safe tries to remove the sub-device, the
> sub-device may appear back and fail-safe cannot plug it in back until
> the removal process is completted. In this time fail-safe may lose the
> primary sub-device services and may hurt application performance.
>
> This patch adds a remove flag check in safe rx_burst function.
> By this way, at most one more hotplug alarm cycle is necessary
> to get the sub-device clean for actual removal.
>
> Fixes: 72a57bfd9a0e ("net/failsafe: add fast burst functions")
> Cc: stable@dpdk.org
>
> Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
> ---
> drivers/net/failsafe/failsafe_rxtx.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/failsafe/failsafe_rxtx.c b/drivers/net/failsafe/failsafe_rxtx.c
> index 7311421..70157c8 100644
> --- a/drivers/net/failsafe/failsafe_rxtx.c
> +++ b/drivers/net/failsafe/failsafe_rxtx.c
> @@ -43,7 +43,8 @@
> {
> return (ETH(sdev) == NULL) ||
> (ETH(sdev)->rx_pkt_burst == NULL) ||
> - (sdev->state != DEV_STARTED);
> + (sdev->state != DEV_STARTED) ||
> + (sdev->remove != 0);
> }
>
> static inline int
> --
> 1.8.3.1
>
--
Gaëtan Rivet
6WIND
next prev parent reply other threads:[~2017-10-26 16:20 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-22 5:51 Matan Azrad
2017-10-26 16:20 ` Gaëtan Rivet [this message]
2017-10-26 19:10 ` Ferruh Yigit
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