linux-kernel - Re: [PATCH HACK RFC] cpu: Prevent late-arriving interrupts from disrupting offline

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: <ea4887fb-cc77-59d4-3ba7-a59f5237ca40@arm.com>
Date:   Mon, 3 Jun 2019 15:39:18 +0200
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Mark Rutland <mark.rutland@....com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     "Paul E. McKenney" <paulmck@...ux.ibm.com>, tglx@...utronix.de,
        mingo@...nel.org, jpoimboe@...hat.com, mojha@...eaurora.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH HACK RFC] cpu: Prevent late-arriving interrupts from
 disrupting offline

On 6/3/19 1:44 PM, Mark Rutland wrote:
> On Mon, Jun 03, 2019 at 10:38:48AM +0200, Peter Zijlstra wrote:
>> On Sat, Jun 01, 2019 at 06:12:53PM -0700, Paul E. McKenney wrote:
>>> Scheduling-clock interrupts can arrive late in the CPU-offline process,
>>> after idle entry and the subsequent call to cpuhp_report_idle_dead().
>>> Once execution passes the call to rcu_report_dead(), RCU is ignoring
>>> the CPU, which results in lockdep complaints when the interrupt handler
>>> uses RCU:
>>
>>> diff --git a/kernel/cpu.c b/kernel/cpu.c
>>> index 448efc06bb2d..3b33d83b793d 100644
>>> --- a/kernel/cpu.c
>>> +++ b/kernel/cpu.c
>>> @@ -930,6 +930,7 @@ void cpuhp_report_idle_dead(void)
>>>   	struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
>>>   
>>>   	BUG_ON(st->state != CPUHP_AP_OFFLINE);
>>> +	local_irq_disable();
>>>   	rcu_report_dead(smp_processor_id());
>>>   	st->state = CPUHP_AP_IDLE_DEAD;
>>>   	udelay(1000);
>>
>> Urgh... I'd almost suggest we do something like the below.
>>
>>
>> But then I started looking at the various arch_cpu_idle_dead()
>> implementations and ran into arm's implementation, which is calling
>> complete() where generic code already established this isn't possible
>> (see for example cpuhp_report_idle_dead()).
> 
> IIRC, that should have been migrated over to cpu_report_death(), as
> arm64 was in commit:
> 
>    05981277a4de1ad6 ("arm64: Use common outgoing-CPU-notification code")
> 
> ... but it looks like Paul's patch to do so [1] fell through the cracks;
> I'm not aware of any reason that shouldn't have been taken.
>    
> [1] https://lore.kernel.org/lkml/1431467407-1223-8-git-send-email-paulmck@linux.vnet.ibm.com/
> 
> Paul, do you want to resend that?

Please do. We're carrying this patch out-of-tree for while now in our 
EAS integration to get cpu hotplug tests passing on TC2 (arm).

-- Dietmar