linux-kernel - Re: [External] Re: [PATCH 2/2] sched: mark PRINTK_DEFERRED_CONTEXT_MASK in _

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: <40ab934e-5b8b-735b-da65-3043efab9fdc@bytedance.com>
Date:   Mon, 28 Sep 2020 16:54:53 +0800
From:   Chengming Zhou <zhouchengming@...edance.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, pmladek@...e.com,
        sergey.senozhatsky@...il.com, rostedt@...dmis.org,
        mingo@...hat.com, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        bsegall@...gle.com, mgorman@...e.de, songmuchun@...edance.com
Subject: Re: [External] Re: [PATCH 2/2] sched: mark
 PRINTK_DEFERRED_CONTEXT_MASK in __schedule()


在 2020/9/28 下午3:32, Peter Zijlstra 写道:
> On Mon, Sep 28, 2020 at 12:11:30AM +0800, Chengming Zhou wrote:
>> The WARN_ON/WARN_ON_ONCE with rq lock held in __schedule() should be
>> deferred by marking the PRINTK_DEFERRED_CONTEXT_MASK, or will cause
>> deadlock on rq lock in the printk path.
> It also shouldn't happen in the first place, so who bloody cares.

Yes, but if our box deadlock just because a WARN_ON_ONCE, we have to
reboot : (

So these WARN_ON_ONCE have BUG_ON effect ?  Or we should change to use
BUG_ON ?

Thanks.

>> Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>
>> Signed-off-by: Muchun Song <songmuchun@...edance.com>
>> ---
>>  kernel/sched/core.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>> index 2d95dc3f4644..81d8bf614225 100644
>> --- a/kernel/sched/core.c
>> +++ b/kernel/sched/core.c
>> @@ -4444,6 +4444,7 @@ static void __sched notrace __schedule(bool preempt)
>>  	 */
>>  	rq_lock(rq, &rf);
>>  	smp_mb__after_spinlock();
>> +	printk_deferred_enter();
>>  
>>  	/* Promote REQ to ACT */
>>  	rq->clock_update_flags <<= 1;
>> @@ -4530,6 +4531,7 @@ static void __sched notrace __schedule(bool preempt)
>>  		rq_unlock_irq(rq, &rf);
>>  	}
>>  
>> +	printk_deferred_exit();
>>  	balance_callback(rq);
>>  }
> NAK printk_deferred is an abomination, kill that.