linux-kernel - Re: [PATCH v2 05/10] um: Determine sleep based on need

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: <20250912005932.2568228-1-tiwei.bie@linux.dev>
Date: Fri, 12 Sep 2025 08:59:32 +0800
From: Tiwei Bie <tiwei.bie@...ux.dev>
To: johannes@...solutions.net
Cc: richard@....at,
	anton.ivanov@...bridgegreys.com,
	benjamin@...solutions.net,
	arnd@...db.de,
	linux-um@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	tiwei.btw@...group.com,
	tiwei.bie@...ux.dev
Subject: Re: [PATCH v2 05/10] um: Determine sleep based on need_resched()

On Thu, 11 Sep 2025 08:59:57 +0200, Johannes Berg wrote:
> On Thu, 2025-09-11 at 12:39 +0800, Tiwei Bie wrote:
> > On Wed, 10 Sep 2025 14:10:37 +0200, Johannes Berg wrote:
> > > On Sun, 2025-08-10 at 13:51 +0800, Tiwei Bie wrote:
> > > > From: Tiwei Bie <tiwei.btw@...group.com>
> > > > 
> > > > With SMP and NO_HZ enabled, the CPU may still need to sleep even
> > > > if the timer is disarmed. Switch to deciding whether to sleep based
> > > > on pending resched. This is a preparation for adding SMP support.
> > > 
> > > What's the rationale for need_resched()? Is that somehow defined for
> > > this? Is it what other architectures use? I guess I'm just not entirely
> > > sure what it means.
> > 
> > Here is a relevant document:
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/scheduler/sched-arch.rst?h=v6.17-rc5#n37
> > 
> > There is a similar check on x86:
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/x86/kernel/process.c?h=v6.17-rc5#n916
> 
> Ah cool, thanks for the pointers. Though "1." part there is a bit
> confusing, I guess I'll send a patch to reword it :)
> 
> FWIW I already applied a few patches, but I'll take another look,
> hopefully today.

Thanks for the review! :)

Regards,
Tiwei