linux-kernel - Re: [PATCH 0/2] sparc64: Use low latency path to resume idle 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] [thread-next>] [day] [month] [year] [list]

Message-Id: <20170721.035526.1236051430538663900.davem@davemloft.net>
Date:   Fri, 21 Jul 2017 03:55:26 +0100 (WEST)
From:   David Miller <davem@...emloft.net>
To:     vijay.ac.kumar@...cle.com
Cc:     sparclinux@...r.kernel.org, rob.gardner@...cle.com,
        anthony.yznaga@...cle.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] sparc64: Use low latency path to resume idle cpu

From: Vijay Kumar <vijay.ac.kumar@...cle.com>
Date: Thu, 20 Jul 2017 21:44:24 -0500

> I had same thoughts initially but I had to go with this approach as
> scheduler_ipi is wrapped with irq_enter() and irq_exit(). Whereas POKE
> resumes the cpu in process context.
> 
> Comments in scheduler_ipi():
> 
>          * Not all reschedule IPI handlers call irq_enter/irq_exit, since
>          * traditionally all their work was done from the interrupt return
>          * path. Now that we actually do some work, we need to make sure
>          * we do call them.
>          *
>          * Some archs already do call them, luckily irq_enter/exit nest
>          * properly.
>          *
>          * Arguably we should visit all archs and update all handlers,
>          * however a fair share of IPIs are still resched only so this would
>          * somewhat pessimize the simple resched case.
>          */
>         irq_enter();
> 

I still think we should be able to fake the state such that this
direct schedule_ipi() call will work.

I could be wrong :)