linux-kernel - Re: [RFC PATCH v2] Softirq:avoid large sched delay from the pending softirqs

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: <87eep32zod.fsf@nanos.tec.linutronix.de>
Date:   Wed, 22 Jul 2020 20:05:22 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     qianjun.kernel@...il.com, peterz@...radead.org, will@...nel.org,
        luto@...nel.org, linux-kernel@...r.kernel.org, urezki@...il.com
Cc:     laoar.shao@...il.com, jun qian <qianjun.kernel@...il.com>
Subject: Re: [RFC PATCH v2] Softirq:avoid large sched delay from the pending softirqs

qianjun.kernel@...il.com writes:
> +
> +		end = ktime_get();
> +		delta = ktime_to_us(end - start);

What's the point of this conversion? That's a division for no value
because you can simply define the maximum time in nanoseconds with the
same effect, i.e.

	ktime_t end = ktime_get() + MAX_SOFTIRQ_TIME_NS;

	if (need_resched() && ktime_get() > end)
		break;

So you can spare all that start, delta and conversion dance and keep the
code simple.

Also notice that need_resched() wants to be evaluated first because
there is no point to do the more expensive time read if need_resched()
is false.

Thanks,

        tglx