From: Thomas Gleixner <tglx@linutronix.de>
To: Juri Lelli <juri.lelli@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
syzbot <syzbot+385468161961cee80c31@syzkaller.appspotmail.com>,
Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
LKML <linux-kernel@vger.kernel.org>,
mingo@redhat.com, nstange@suse.de,
syzkaller-bugs@googlegroups.com, juri.lelli@redhat.com
Subject: Re: INFO: rcu detected stall in do_idle
Date: Tue, 16 Oct 2018 16:45:00 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.21.1810161643540.7787@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20181016144045.GF9130@localhost.localdomain>
On Tue, 16 Oct 2018, Juri Lelli wrote:
> On 16/10/18 16:03, Peter Zijlstra wrote:
> > On Tue, Oct 16, 2018 at 03:24:06PM +0200, Thomas Gleixner wrote:
> > > It does reproduce here but with a kworker stall. Looking at the reproducer:
> > >
> > > *(uint32_t*)0x20000000 = 0;
> > > *(uint32_t*)0x20000004 = 6;
> > > *(uint64_t*)0x20000008 = 0;
> > > *(uint32_t*)0x20000010 = 0;
> > > *(uint32_t*)0x20000014 = 0;
> > > *(uint64_t*)0x20000018 = 0x9917;
> > > *(uint64_t*)0x20000020 = 0xffff;
> > > *(uint64_t*)0x20000028 = 0;
> > > syscall(__NR_sched_setattr, 0, 0x20000000, 0);
> > >
> > > which means:
> > >
> > > struct sched_attr {
> > > .size = 0,
> > > .policy = 6,
> > > .flags = 0,
> > > .nice = 0,
> > > .priority = 0,
> > > .deadline = 0x9917,
> > > .runtime = 0xffff,
> > > .period = 0,
> > > }
> > >
> > > policy 6 is SCHED_DEADLINE
> > >
> > > That makes the thread hog the CPU and prevents all kind of stuff to run.
> > >
> > > Peter, is that expected behaviour?
> >
> > Sorta, just like FIFO-99 while(1);. Except we should be rejecting the
> > above configuration, because of the rule:
> >
> > runtime <= deadline <= period
> >
> > Juri, where were we supposed to check that?
>
> Not if period == 0.
>
> https://elixir.bootlin.com/linux/latest/source/kernel/sched/deadline.c#L2632
> https://elixir.bootlin.com/linux/latest/source/kernel/sched/deadline.c#L2515
>
> Now, maybe we should be checking also against the default 95% cap?
If the cap is active, then yes. But you want to use the actual
configuration not the default.
Thanks,
tglx
next prev parent reply other threads:[~2018-10-16 14:45 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-13 7:31 INFO: rcu detected stall in do_idle syzbot
2018-10-16 13:24 ` Thomas Gleixner
2018-10-16 14:03 ` Peter Zijlstra
2018-10-16 14:41 ` Juri Lelli
2018-10-16 14:45 ` Thomas Gleixner [this message]
2018-10-16 15:36 ` Juri Lelli
2018-10-18 8:28 ` Juri Lelli
2018-10-18 9:48 ` Peter Zijlstra
2018-10-18 10:10 ` Juri Lelli
2018-10-18 10:38 ` luca abeni
2018-10-18 10:33 ` luca abeni
2018-10-19 13:14 ` Peter Zijlstra
2018-10-18 10:23 ` luca abeni
2018-10-18 10:47 ` Juri Lelli
2018-10-18 11:08 ` luca abeni
2018-10-18 12:21 ` Juri Lelli
2018-10-18 12:36 ` luca abeni
2018-10-19 11:39 ` Peter Zijlstra
2018-10-19 20:50 ` luca abeni
2018-10-24 12:03 ` Juri Lelli
2018-10-27 11:16 ` Dmitry Vyukov
2018-10-28 8:33 ` Juri Lelli
2018-10-30 10:45 ` Peter Zijlstra
2018-10-30 11:08 ` luca abeni
2018-10-31 16:18 ` Daniel Bristot de Oliveira
2018-10-31 16:40 ` Juri Lelli
2018-10-31 17:39 ` Peter Zijlstra
2018-10-31 17:58 ` Daniel Bristot de Oliveira
2018-11-01 5:55 ` Juri Lelli
2018-11-02 10:00 ` Daniel Bristot de Oliveira
2018-11-05 10:55 ` Juri Lelli
2018-11-07 10:12 ` Daniel Bristot de Oliveira
2018-10-31 17:38 ` Peter Zijlstra
2018-10-30 11:12 ` Juri Lelli
2018-11-06 11:44 ` Juri Lelli
2021-10-27 0:59 Hao Sun
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=alpine.DEB.2.21.1810161643540.7787@nanos.tec.linutronix.de \
--to=tglx@linutronix.de \
--cc=bp@alien8.de \
--cc=hpa@zytor.com \
--cc=juri.lelli@gmail.com \
--cc=juri.lelli@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=nstange@suse.de \
--cc=peterz@infradead.org \
--cc=syzbot+385468161961cee80c31@syzkaller.appspotmail.com \
--cc=syzkaller-bugs@googlegroups.com \
/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).