From: Dmitry Vyukov <dvyukov@google.com>
To: Hillf Danton <hdanton@sina.com>
Cc: Johannes Berg <johannes@sipsolutions.net>,
syzbot <syzbot+27df43cf7ae73de7d8ee@syzkaller.appspotmail.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-wireless <linux-wireless@vger.kernel.org>,
syzkaller-bugs <syzkaller-bugs@googlegroups.com>
Subject: Re: BUG: soft lockup in ieee80211_tasklet_handler
Date: Wed, 3 Mar 2021 10:06:51 +0100 [thread overview]
Message-ID: <CACT4Y+ZEdh6WJB8b5dg+jgv7thnrt=pVW6BzPngOyT3KKMaMtw@mail.gmail.com> (raw)
In-Reply-To: <20210303085912.1647-1-hdanton@sina.com>
On Wed, Mar 3, 2021 at 9:59 AM Hillf Danton <hdanton@sina.com> wrote:
>
> On Tue, 02 Mar 2021 15:18:16 +0100 Johannes Berg wrote:
> > On Wed, 2021-02-24 at 10:30 +0800, Hillf Danton wrote:
> > >
> > > Add budget for the 80211 softint handler - it's feasible not to try to
> > > build the giant pyramid in a week.
> > >
> > > --- x/net/mac80211/main.c
> > > +++ y/net/mac80211/main.c
> > > @@ -224,9 +224,15 @@ static void ieee80211_tasklet_handler(un
> > > {
> > > struct ieee80211_local *local = (struct ieee80211_local *) data;
> > > struct sk_buff *skb;
> > > + int i = 0;
> > > +
> > > + while (i++ < 64) {
> > > + skb = skb_dequeue(&local->skb_queue);
> > > + if (!skb)
> > > + skb = skb_dequeue(&local->skb_queue_unreliable);
> > > + if (!skb)
> > > + return;
> >
> > I guess that's not such a bad idea, but I do wonder how we get here,
> > userspace can submit packets faster than we can process?
>
> I wonder why syzbot did not make other handlers stand out than
> ieee80211_tasklet_handler.
syzbot has no relation to this whatsoever. It's just a proxy between
the kernel and you. Ask the kernel ;)
> > It feels like a simulation-only case, tbh, since over the air you have
> > limits how much bandwidth you can get ... unless you have a very slow
> > CPU?
>
> Even with a slower CPU I want to run a FIFO task every tick - it can bear
> latencies like two seconds.
> >
> > In any case, if you want anything merged you're going to have to submit
> > a proper patch with a real commit message and Signed-off-by, etc.
> >
> > johannes
prev parent reply other threads:[~2021-03-03 14:40 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-23 17:55 BUG: soft lockup in ieee80211_tasklet_handler syzbot
2021-03-02 8:10 ` syzbot
[not found] ` <20210224023026.3001-1-hdanton@sina.com>
2021-03-02 14:18 ` Johannes Berg
2021-03-02 19:01 ` Dmitry Vyukov
2021-03-04 8:30 ` Johannes Berg
[not found] ` <20210303085912.1647-1-hdanton@sina.com>
2021-03-03 9:06 ` Dmitry Vyukov [this message]
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