linux-kernel - Re: [PATCH] sched/fair: Optimize select_idle

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]

Date:   Fri, 13 Dec 2019 09:51:30 +0800
From:   "chengjian (D)" <cj.chengjian@...wei.com>
To:     Peter Zijlstra <peterz@...radead.org>
CC:     <mingo@...nel.org>, <linux-kernel@...r.kernel.org>,
        <chenwandun@...wei.com>, <xiexiuqi@...wei.com>,
        <liwei391@...wei.com>, <huawei.libin@...wei.com>,
        <bobo.shaobowang@...wei.com>, <juri.lelli@...hat.com>,
        <vincent.guittot@...aro.org>
Subject: Re: [PATCH] sched/fair: Optimize select_idle_cpu


On 2019/12/12 23:04, Peter Zijlstra wrote:
> On Thu, Dec 12, 2019 at 10:41:02PM +0800, Cheng Jian wrote:
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index 08a233e97a01..16a29b570803 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -5834,6 +5834,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
>>   	s64 delta;
>>   	int this = smp_processor_id();
>>   	int cpu, nr = INT_MAX, si_cpu = -1;
>> +	struct cpumask cpus;
> NAK, you must not put a cpumask on stack.
>
> .

Hi, Peter

     I saw the same work in select_idle_core, and I was wondering why 
the per_cpu variable was

needed for this yesterday. Now I think I probably understand : cpumask 
may be too large,

putting it on the stack may cause overflow. Is this correct ?

     I'm sorry I made a mistake like this. I will fix it in v2

     Thank you very much.


         -- Cheng Jian