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From: Thomas Monjalon <thomas@monjalon.net>
To: Stephen Hemminger <stephen@networkplumber.org>,
	Ferruh Yigit <ferruh.yigit@intel.com>
Cc: dev@dpdk.org, stable@dpdk.org
Subject: Re: [dpdk-dev] [PATCH] kni: fix kernel deadlock when using mlx devices
Date: Wed, 18 Mar 2020 16:17:57 +0100	[thread overview]
Message-ID: <3101970.h16uAIiOU7@xps> (raw)
In-Reply-To: <ffa192d1-99d7-a636-c1bf-7f64dfde91b4@intel.com>

17/01/2020 17:43, Ferruh Yigit:
> On 12/22/2019 5:55 PM, Stephen Hemminger wrote:
> > This fixes a deadlock when using KNI with bifurcated drivers.
> > Bringing kni device up always times out when using Mellanox
> > devices.
> > 
> > The kernel KNI driver sends message to userspace to complete
> > the request. For the case of bifurcated driver, this may involve
> > an additional request to kernel to change state. This request
> > would deadlock because KNI was holding the RTNL mutex.
> > 
> > This was a bad design which goes back to the original code.
> > A workaround is for KNI driver to drop RTNL while waiting.
> > To prevent the device from disappearing while the operation
> > is in progress, it needs to hold reference to network device
> > while waiting.
> > 
> > As an added benefit, an useless error check can also be removed.
> > 
> > Fixes: 3fc5ca2f6352 ("kni: initial import")
> > Cc: stable@dpdk.org
> > Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> > ---
> 
> This patch cause a hang on my server, not sure what exactly was the problem but
> kernel log was continuously printing "Cannot send to req_q". Will dig more.

Ferruh, did you have a chance to check what is hanging?
Stephen, is there any news on your side?



  reply	other threads:[~2020-03-18 15:18 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-22 17:55 Stephen Hemminger
2020-01-17 16:43 ` Ferruh Yigit
2020-03-18 15:17   ` Thomas Monjalon [this message]
2020-05-06  0:14     ` Stephen Hemminger
2020-07-27 17:33       ` Ferruh Yigit
2020-07-27 17:52         ` Stephen Hemminger
2020-07-28  8:56           ` Igor Ryzhov

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