linux-kernel - Re: [PATCH v2 1/2] smp: Introduce a helper function to check for pending IPIs

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: <a0120876-0f00-4e1a-aa17-5fe7c3512276@arm.com>
Date: Mon, 20 Oct 2025 20:10:58 +0100
From: Ben Horgan <ben.horgan@....com>
To: Ulf Hansson <ulf.hansson@...aro.org>,
 "Rafael J . Wysocki" <rafael@...nel.org>,
 Thomas Gleixner <tglx@...utronix.de>
Cc: Mark Rutland <mark.rutland@....com>, Marc Zyngier <maz@...nel.org>,
 Maulik Shah <quic_mkshah@...cinc.com>, Sudeep Holla <sudeep.holla@....com>,
 Daniel Lezcano <daniel.lezcano@...aro.org>,
 Vincent Guittot <vincent.guittot@...aro.org>, linux-pm@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] smp: Introduce a helper function to check for
 pending IPIs

Hi Ulf,

Only a comment on the naming rather than a full review.

On 10/20/25 15:17, Ulf Hansson wrote:
> When governors used during cpuidle, tries to find the most optimal
> idlestate for a CPU or a group of CPUs, they are known to quite often fail.
> One reason for this, is that we are not taking into account whether there
> has been an IPI scheduled for any of the CPUs that are affected by the
> selected idlestate.
> 
> To enable pending IPIs to be taken into account for cpuidle decisions,
> let's introduce a new helper function, cpus_may_have_pending_ipi().

To me, "may" indicates permission, i.e. is allowed, rather than
correctness. Would "likely" be better here, cpus_likely_have_pending_ipi()?

> 
> Note that, the implementation is intentionally as lightweight as possible,
> in favor of always providing the correct information. For cpuidle decisions
> this is good enough.
> 
> Suggested-by: Thomas Gleixner <tglx@...utronix.de>
> Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
> ---
> 
> Changes in v2:
> 	- Implemented a common function, rather than making it arch-specific. As
> 	suggested by Thomas and Marc.
> 	- Renamed the function to indicate that it doesn't provide correctness.
> 	- Clarified function description and commit message.
> 
-- 
Thanks,

Ben