linux-kernel - Re: Debugging Thinkpad T430s occasional suspend failure.

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: <CAFTL4hzUy+2qDaCDK3jCUs+6Fe48-uU9KSB+Ssk+-i=zYhqaRg@mail.gmail.com>
Date:	Sun, 17 Feb 2013 22:02:11 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Dave Jones <davej@...hat.com>, Hugh Dickins <hughd@...gle.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Paul McKenney <paul.mckenney@...aro.org>
Subject: Re: Debugging Thinkpad T430s occasional suspend failure.

2013/2/17 Frederic Weisbecker <fweisbec@...il.com>:
> 2013/2/17 Linus Torvalds <torvalds@...ux-foundation.org>:
>> On Sun, Feb 17, 2013 at 7:11 AM, Frederic Weisbecker <fweisbec@...il.com> wrote:
>>>
>>> preempt_value_in_interrupt() looks buggy in your patch: it makes
>>> invoke_softirq() returning if (val & HARDIRQ_MASK). But that's always
>>> true since you have moved further the sub_preempt_count(IRQ_EXIT)
>>> further.
>>
>> No, that's not it. The value hasn't been written back yet, but it already did:
>>
>> +       int offset = IRQ_EXIT_OFFSET;
>> +       int count = preempt_count() - offset;
>>
>> so the 'count' has the IRQ_EXIT_OFFSET already subtracted. So no,
>> HARDIRQ_MASK is *not* always set.
>
> Another thing. Perhaps we can push the idea of your patch a little
> further by re-entering HARDIRQ_OFFSET at the end of the softirq
> processing and do the final sub_preempt_count(HARDIRQ_OFFSET) at the
> very end of irq_exit().
>
> This way irq_exit() looks a bit more simple to me: everything there
> becomes considered as in hardirq: (ie: rcu_irq_exit() and
> tick_nohz_irq_exit() won't appear anymore as weird special cases) and
> we get rid of that IRQ_EXIT_OFFSET hack that fixes the CONFIG_PREEMPT
> case.
>
> I'm attaching an untested patch that modify yours. It's probably
> missing some corner cases that rely on in_interrupt() value in
> rcu_irq_exit() and tick_nohz_irq_exit() and may be other things.

I messed up preempt_offset_in_interrupt() with in_atomic() code
instead of in_interrupt(). Anyway the patch is untested and is more
there to get your opinion for now. I'll put some more care on it if
people like it.
--
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/