linux-kernel - Re: [tip:sched/locking] sched: Add p->pi_lock to task_rq

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4DEB58D8.4000805@die-jansens.de>
Date:	Sun, 05 Jun 2011 12:22:16 +0200
From:	Arne Jansen <lists@...-jansens.de>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	mingo@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
	efault@....de, npiggin@...nel.dk, akpm@...ux-foundation.org,
	frank.rowand@...sony.com, tglx@...utronix.de,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:sched/locking] sched: Add p->pi_lock to task_rq_lock()

On 05.06.2011 11:55, Ingo Molnar wrote:
>
> * Arne Jansen<lists@...-jansens.de>  wrote:
>
>>> ( Arne, please also double check on a working bootup that the NMI
>>>    watchdog is actually ticking, by checking the NMI counts in
>>>    /proc/interrupts go up slowly but surely on all CPUs. )
>>
>> It does, but _very_ slowly. Some CPUs do not count up for tens of
>> minutes if the machine is idle. If I generate some load like 'make
>> tags', the counters go up quite quickly.
>> After 4 minutes and one 'make cscope' it looks like this:
>> NMI:          8         13         43          5          2
>> 3        22          1   Non-maskable interrupts
>>
>> But I never see a single tick on console or in dmesg, even when I
>> replace the early_printk with a printk.
>
> hm, that might be because the NMI watchdog uses halted cycles to
> tick.
>
> That's not a problem (the kernel cannot lock up while there are no
> cycles ticking) but nevertheless could you work this around please
> by starting 8 infinite shell loops:
>
>     for ((i=0; i<8; i++)); do while : ; do : ; done&  done
>
> ?
>
> This will saturate all cores and makes sure the NMI watchdog is
> ticking everywhere.
>
> Hopefully this wont make the bug go away :-)
>

OK, now we get going. I get the ticks, the bug is still there, and
all CPUs still tick after the lockup. I also added an early_printk
inside the lockup-if, and it reports hard lockups. At first for only
one or 2 CPUs, and after some time all CPUs are locked up.

-Arne
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/