linux-kernel - Re: INFO: rcu detected stall in cleanup

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Message-ID: <20200909155105.5efb291a@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Wed, 9 Sep 2020 15:51:05 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Vinicius Costa Gomes <vinicius.gomes@...el.com>
Cc:     syzbot <syzbot+8267241609ae8c23b248@...kaller.appspotmail.com>,
        davem@...emloft.net, jhs@...atatu.com, jiri@...nulli.us,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        syzkaller-bugs@...glegroups.com, tglx@...utronix.de,
        xiyou.wangcong@...il.com
Subject: Re: INFO: rcu detected stall in cleanup_net (4)

On Wed, 09 Sep 2020 14:54:36 -0700 Vinicius Costa Gomes wrote:
> > Vinicius, could you please take a look at all the syzbot reports which
> > point to your commit? I know syzbot bisection is not super reliable,
> > but at least 3 reports point to your commit now, so something's
> > probably going on.  
> 
> I did take a look, and it seems that it all boils down to having too
> small (unreasonable?) intervals in the schedule, which causes the
> hrtimer handler to starve the other kernel threads.
> 
> I have a quick fix to restrict the interval values to more sensible
> values (at least equal to the time it takes to transmit the mininum
> ethernet frame size), I am testing it and I will propose it soon. But a
> proper solution will require more time.

Great, thank you!