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From: Sukadev Bhattiprolu <sukadev@linux.ibm.com>
To: Jakub Kicinski <kuba@kernel.org>
Cc: "Dany Madden" <drt@linux.ibm.com>,
	"Xuan Zhuo" <xuanzhuo@linux.alibaba.com>,
	netdev@vger.kernel.org, linyunsheng@huawei.com,
	"David S. Miller" <davem@davemloft.net>,
	"Eric Dumazet" <edumazet@google.com>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	"Antoine Tenart" <atenart@kernel.org>,
	"Alexander Lobakin" <alobakin@pm.me>,
	"Wei Wang" <weiwan@google.com>, "Taehee Yoo" <ap420073@gmail.com>,
	"Björn Töpel" <bjorn@kernel.org>, "Arnd Bergmann" <arnd@arndb.de>,
	"Kumar Kartikeya Dwivedi" <memxor@gmail.com>,
	"Neil Horman" <nhorman@redhat.com>,
	"Dust Li" <dust.li@linux.alibaba.com>
Subject: Re: [PATCH net v2] napi: fix race inside napi_enable
Date: Mon, 18 Oct 2021 17:01:27 -0700	[thread overview]
Message-ID: <YW4K1/O51V/5/q1w@us.ibm.com> (raw)
In-Reply-To: <20211018164723.02919102@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>

Jakub Kicinski [kuba@kernel.org] wrote:
> On Mon, 18 Oct 2021 16:36:36 -0700 Dany Madden wrote:
> > > The BUG_ON() is here to make sure that when napi_enable() is called the
> > > napi instance was dormant, i.e. disabled. We have "STATE_SCHED" bit set
> > > on disabled NAPIs because that bit means ownership. Whoever disabled
> > > the NAPI owns it.
> > > 
> > > That BUG_ON() could have been taken outside of the loop, there's no
> > > point re-checking on every try.
> > > 
> > > Are you seeing NAPI-related failures? We had at least 3 reports in the
> > > last two weeks of strange failures which look like NAPI state getting
> > > corrupted on net-next...  
> > 
> > We hit two napi related crashes while attempting mtu size change.

BTW these are with a couple of bug fixes in ibmvnic driver applied
to 1e0083bd0777 ("gve: DQO: avoid unused variable warnings").

We are trying to narrow it down to the following change that is
required to be able to change mtu on ibmvnic.

> 
> Is it reproducible or happens rarely and randomly?

Random. We have been testing for a couple of weeks but hit both today.

Sukadev

---
index 8f17096e614d..a1533979c670 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -1914,8 +1914,6 @@ static netdev_tx_t ibmvnic_xmit(struct sk_buff *skb, struct net_device *netdev)
        ind_bufp = &tx_scrq->ind_buf;
 
        if (test_bit(0, &adapter->resetting)) {
-               if (!netif_subqueue_stopped(netdev, skb))
-                       netif_stop_subqueue(netdev, queue_num);
                dev_kfree_skb_any(skb);
 

  reply	other threads:[~2021-10-19  0:02 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-18  8:52 Xuan Zhuo
2021-09-20  8:50 ` patchwork-bot+netdevbpf
2021-09-20 19:20 ` Jakub Kicinski
2021-09-22  6:47   ` Xuan Zhuo
2021-09-23 13:14     ` Jakub Kicinski
     [not found]       ` <1632404456.506512-1-xuanzhuo@linux.alibaba.com>
2021-09-23 14:54         ` Jakub Kicinski
2021-10-18 21:58 ` Sukadev Bhattiprolu
2021-10-18 22:55   ` Jakub Kicinski
2021-10-18 23:36     ` Dany Madden
2021-10-18 23:47       ` Jakub Kicinski
2021-10-19  0:01         ` Sukadev Bhattiprolu [this message]
2021-10-22  3:16       ` Sukadev Bhattiprolu
2021-10-25 17:36         ` Jakub Kicinski

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