From: Ferruh Yigit <ferruh.yigit@intel.com>
To: Elad Nachman <eladv6@gmail.com>
Cc: dev@dpdk.org, Igor Ryzhov <iryzhov@nfware.com>,
Stephen Hemminger <stephen@networkplumber.org>
Subject: Re: [dpdk-dev] [PATCH] kni: fix rtnl deadlocks and race conditions
Date: Fri, 19 Feb 2021 18:41:54 +0000 [thread overview]
Message-ID: <9f7284a8-4158-c246-c329-bfec27f543a5@intel.com> (raw)
In-Reply-To: <20201126144613.4986-1-eladv6@gmail.com>
On 11/26/2020 2:46 PM, Elad Nachman wrote:
> This patch leverages on Stephen Hemminger's 64106 patch from Dec 2019,
> and fixes the issues reported by Ferruh and Igor:
>
> A. KNI sync lock is being locked while rtnl is held.
> If two threads are calling kni_net_process_request() ,
> then the first one wil take the sync lock, release rtnl lock then sleep.
> The second thread will try to lock sync lock while holding rtnl.
> The first thread will wake, and try to lock rtnl, resulting in a deadlock.
> The remedy is to release rtnl before locking the KNI sync lock.
> Since in between nothing is accessing Linux network-wise,
> no rtnl locking is needed.
Hi Elad,
Thanks for explanation, that clarifies the issue.
Also I confirm I don't see the hang, at least as much as I test.
>
> B. There is a race condition in __dev_close_many() processing the
> close_list while the application terminates.
> It looks like if two vEth devices are terminating,
> and one releases the rtnl lock, the other takes it,
> updating the close_list in an unstable state,
> causing the close_list to become a circular linked list,
> hence list_for_each_entry() will endlessly loop inside
> __dev_close_many() .
> Since the description for the original patch indicate the
> original motivation was bringing the device up,
> I have changed kni_net_process_request() to hold the rtnl mutex
> in case of bringing the device down since this is the path called
> from __dev_close_many() , causing the corruption of the close_list.
>
I can't reproduce this case, I see the protection in the code, but better to get
confirmation from Igor.
Overall the issue seems calling a function pointed by 'rte_kni_ops' which
requires to acquire the rtnl lock.
So I wonder if this can't be handled in the ops function, by processing the
request asynchronously,
like recording the request, return from 'rte_kni_ops', and process the request
afterwards?
I assume the application we mention is not kni sample application.
>
>
> Signed-off-by: Elad Nachman <eladv6@gmail.com>
> ---
> kernel/linux/kni/kni_net.c | 47 +++++++++++++++++++++++++-------------
> 1 file changed, 31 insertions(+), 16 deletions(-)
>
> diff --git a/kernel/linux/kni/kni_net.c b/kernel/linux/kni/kni_net.c
> index 4b752083d..cf5b0845d 100644
> --- a/kernel/linux/kni/kni_net.c
> +++ b/kernel/linux/kni/kni_net.c
> @@ -17,6 +17,7 @@
> #include <linux/skbuff.h>
> #include <linux/kthread.h>
> #include <linux/delay.h>
> +#include <linux/rtnetlink.h>
>
> #include <rte_kni_common.h>
> #include <kni_fifo.h>
> @@ -102,18 +103,26 @@ get_data_kva(struct kni_dev *kni, void *pkt_kva)
> * It can be called to process the request.
> */
> static int
> -kni_net_process_request(struct kni_dev *kni, struct rte_kni_request *req)
> +kni_net_process_request(struct net_device *dev, struct rte_kni_request *req)
> {
> + struct kni_dev *kni = netdev_priv(dev);
> int ret = -1;
> void *resp_va;
> uint32_t num;
> int ret_val;
> + int req_is_dev_stop = 0;
>
> - if (!kni || !req) {
> - pr_err("No kni instance or request\n");
> - return -EINVAL;
> - }
> + if (req->req_id == RTE_KNI_REQ_CFG_NETWORK_IF &&
> + req->if_up == 0)
> + req_is_dev_stop = 1;
>
> + ASSERT_RTNL();
> +
> + if (!req_is_dev_stop) {
> + dev_hold(dev);
> + rtnl_unlock();
> + }
> +
> mutex_lock(&kni->sync_lock);
>
> /* Construct data */
> @@ -125,8 +134,13 @@ kni_net_process_request(struct kni_dev *kni, struct rte_kni_request *req)
> goto fail;
> }
>
> + /* Since we need to wait and RTNL mutex is held
> + * drop the mutex and hold refernce to keep device
> + */
> +
Comment seems left here, need to go up. s/refernce/reference
> ret_val = wait_event_interruptible_timeout(kni->wq,
> kni_fifo_count(kni->resp_q), 3 * HZ);
> +
> if (signal_pending(current) || ret_val <= 0) {
> ret = -ETIME;
> goto fail;
> @@ -144,6 +158,13 @@ kni_net_process_request(struct kni_dev *kni, struct rte_kni_request *req)
>
> fail:
> mutex_unlock(&kni->sync_lock);
> +
> +
extra empty line
> + if (!req_is_dev_stop) {
> + rtnl_lock();
> + dev_put(dev);
> + }
> +
> return ret;
> }
>
> @@ -155,7 +176,6 @@ kni_net_open(struct net_device *dev)
> {
> int ret;
> struct rte_kni_request req;
> - struct kni_dev *kni = netdev_priv(dev);
>
> netif_start_queue(dev);
> if (kni_dflt_carrier == 1)
> @@ -168,7 +188,7 @@ kni_net_open(struct net_device *dev)
>
> /* Setting if_up to non-zero means up */
> req.if_up = 1;
> - ret = kni_net_process_request(kni, &req);
> + ret = kni_net_process_request(dev, &req);
>
Althoug it is not soo confusing, these lines and following ones are noise for
this patch, they are just for 'kni_net_process_request' paramter change.
What do you think do the 'kni_net_process_request' parameter change in first
patch, and fix the issue in second, this way second patch can contain only the
actual changes required for fix.
next prev parent reply other threads:[~2021-02-19 18:42 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-26 14:46 Elad Nachman
2021-02-19 18:41 ` Ferruh Yigit [this message]
2021-02-21 8:03 ` Elad Nachman
2021-02-22 15:58 ` Ferruh Yigit
2021-02-23 12:05 ` [dpdk-dev] [PATCH V2] kni: fix rtnl deadlocks and race conditions v2 Elad Nachman
2021-02-23 12:53 ` Ferruh Yigit
2021-02-23 13:44 ` [dpdk-dev] [PATCH 1/2] kni: fix rtnl deadlocks and race conditions v3 Elad Nachman
2021-02-23 13:45 ` [dpdk-dev] [PATCH 2/2] " Elad Nachman
2021-02-24 12:49 ` Igor Ryzhov
2021-02-24 13:33 ` Elad Nachman
2021-02-24 14:04 ` Igor Ryzhov
2021-02-24 14:06 ` Elad Nachman
2021-02-24 14:41 ` Igor Ryzhov
2021-02-24 14:56 ` Elad Nachman
2021-02-24 15:18 ` Igor Ryzhov
[not found] ` <CACXF7qkhkzFc-=v=iiBzh2V7rLjk1U34VUfPbNrnYJND_0TKHQ@mail.gmail.com>
2021-02-24 16:31 ` Igor Ryzhov
2021-02-24 15:54 ` Stephen Hemminger
2021-02-25 14:32 ` [dpdk-dev] [PATCH 1/2] kni: fix kernel deadlock when using mlx devices Elad Nachman
2021-02-25 14:32 ` [dpdk-dev] [PATCH 2/2] kni: fix rtnl deadlocks and race conditions v4 Elad Nachman
2021-02-25 21:01 ` Igor Ryzhov
2021-02-26 15:48 ` Stephen Hemminger
2021-02-26 17:43 ` Elad Nachman
2021-03-01 8:10 ` Igor Ryzhov
2021-03-01 16:38 ` Stephen Hemminger
2021-03-15 16:58 ` Ferruh Yigit
2021-03-01 20:27 ` Dan Gora
2021-03-01 21:26 ` Dan Gora
2021-03-02 16:44 ` Elad Nachman
2021-03-15 17:17 ` Ferruh Yigit
2021-03-16 18:35 ` Elad Nachman
2021-03-16 18:42 ` Ferruh Yigit
2021-03-15 17:17 ` [dpdk-dev] [PATCH 1/2] kni: fix kernel deadlock when using mlx devices Ferruh Yigit
2021-03-29 14:36 ` [dpdk-dev] [PATCH v5 1/3] kni: refactor user request processing Ferruh Yigit
2021-03-29 14:36 ` [dpdk-dev] [PATCH v5 2/3] kni: support async user request Ferruh Yigit
2021-03-29 14:36 ` [dpdk-dev] [PATCH v5 3/3] kni: fix kernel deadlock when using mlx devices Ferruh Yigit
2021-04-09 14:56 ` [dpdk-dev] [dpdk-stable] " Ferruh Yigit
2021-04-12 14:35 ` Elad Nachman
2021-04-20 23:07 ` Thomas Monjalon
2021-04-23 8:41 ` Igor Ryzhov
2021-04-23 8:59 ` Ferruh Yigit
2021-04-23 12:43 ` Igor Ryzhov
2021-04-23 12:58 ` Igor Ryzhov
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=9f7284a8-4158-c246-c329-bfec27f543a5@intel.com \
--to=ferruh.yigit@intel.com \
--cc=dev@dpdk.org \
--cc=eladv6@gmail.com \
--cc=iryzhov@nfware.com \
--cc=stephen@networkplumber.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).