linux-kernel - Re: [PATCH 3/3] LoongArch: Allow to enable PREEMPT

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: <20241114113018.Ilo9ZsQo@linutronix.de>
Date: Thu, 14 Nov 2024 12:30:18 +0100
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: Huacai Chen <chenhuacai@...ngson.cn>, Xuerui Wang <kernel@...0n.name>,
	loongarch@...ts.linux.dev, Clark Williams <clrkwllms@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	linux-rt-devel@...ts.linux.dev, Guo Ren <guoren@...nel.org>,
	Jiaxun Yang <jiaxun.yang@...goat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] LoongArch: Allow to enable PREEMPT_RT

On 2024-11-14 19:19:26 [+0800], Huacai Chen wrote:
> > > > Why is ntpd/chronyd service affecting this? Is it running at prio 99?
> > > > Otherwise it should not be noticed.
> > > No, ntpd/chronyd doesn't affect latency. But they may trigger RTC
> > > synchronization every 11 minutes, and RTC synchronization affects
> > > latency. We can keep ntpd/chronyd running but disable RTC
> > > synchronization by configuration, this is the least aggressive method.
> >
> > What is "RTC synchronization" in this context?
> Means the sync_hw_clock() function in kernel/time/ntp.c, it can be
> enabled/disabled by chronyd configuration:

But what exactly is sync_hw_clock() doing that is causing a problem
here? The clock on HW is updated. The access to the RTC clock is
preemptible.

> Huacai

Sebastian