linux-kernel - RE: [PATCH V2] arm64: psci: Reduce waiting time of cpu_psci_cpu

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] [day] [month] [year] [list]

Date:   Thu, 17 Oct 2019 14:25:14 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Yunfeng Ye' <yeyunfeng@...wei.com>,
        Sudeep Holla <sudeep.holla@....com>
CC:     "catalin.marinas@....com" <catalin.marinas@....com>,
        "will@...nel.org" <will@...nel.org>,
        "kstewart@...uxfoundation.org" <kstewart@...uxfoundation.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "ard.biesheuvel@...aro.org" <ard.biesheuvel@...aro.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "wuyun.wu@...wei.com" <wuyun.wu@...wei.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "hushiyuan@...wei.com" <hushiyuan@...wei.com>,
        "linfeilong@...wei.com" <linfeilong@...wei.com>
Subject: RE: [PATCH V2] arm64: psci: Reduce waiting time of
 cpu_psci_cpu_kill()

From: Yunfeng Ye
 > Sent: 17 October 2019 15:20
> On 2019/10/17 22:00, David Laight wrote:
> > From: Yunfeng Ye
> >> Sent: 17 October 2019 14:26
> > ...
> >>>> -	for (i = 0; i < 10; i++) {
> >>>> +	i = 0;
> >>>> +	timeout = jiffies + msecs_to_jiffies(100);
> >>>> +	do {
> >>>>  		err = psci_ops.affinity_info(cpu_logical_map(cpu), 0);
> >>>>  		if (err == PSCI_0_2_AFFINITY_LEVEL_OFF) {
> >>>>  			pr_info("CPU%d killed.\n", cpu);
> >>>>  			return 0;
> >>>>  		}
> >>>>
> >>>> -		msleep(10);
> >>>> -		pr_info("Retrying again to check for CPU kill\n");
> >>>
> >>> You dropped this message, any particular reason ?
> >>>
> >> When reduce the time interval to 1ms, the print message maybe increase 10 times.
> >> on the other hand, cpu_psci_cpu_kill() will print message on success or failure, which
> >> this retry log is not very necessary. of cource, I think use pr_info_once() instead of
> >> pr_info() is better.
> >
> > Maybe you should print in on (say) the 10th time around the loop.
> >
> Can it like this:
>   pr_info("CPU%d killed with %d loops.\n", cpu, loops);
> 
> If put the number of waiting times in the successful printing message, it is
> not necessary to print the "Retrying ..." message.

That depends on whether you want to know how long it took or why the system
is 'stuck'.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)