linux-kernel - Re: [PATCH v4 4/4] arm: defconfig: drop RT_GROUP

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] [day] [month] [year] [list]

Message-ID: <CAAhV-H4fTGs-7EXE0EcR=P6GqHF2fokRE-kEte+cDmhjy=FYsA@mail.gmail.com>
Date: Tue, 18 Mar 2025 19:57:44 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Thierry Reding <thierry.reding@...il.com>
Cc: Arnd Bergmann <arnd@...db.de>, Celeste Liu <uwu@...lacanthus.name>, 
	Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, 
	Albert Ou <aou@...s.berkeley.edu>, Guo Ren <guoren@...nel.org>, 
	Anup Patel <anup@...infault.org>, 
	Heinrich Schuchardt <heinrich.schuchardt@...onical.com>, WANG Xuerui <kernel@...0n.name>, 
	Yoshinori Sato <ysato@...rs.sourceforge.jp>, Rich Felker <dalias@...c.org>, 
	John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>, Russell King <linux@...linux.org.uk>, 
	Florian Fainelli <florian.fainelli@...adcom.com>, 
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>, Ray Jui <rjui@...adcom.com>, 
	Scott Branden <sbranden@...adcom.com>, Tony Lindgren <tony@...mide.com>, 
	Jonathan Hunter <jonathanh@...dia.com>, Aaro Koskinen <aaro.koskinen@....fi>, 
	Andreas Kemnade <andreas@...nade.info>, Kevin Hilman <khilman@...libre.com>, 
	Roger Quadros <rogerq@...nel.org>, Palmer Dabbelt <palmer@...osinc.com>, linux-riscv@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, loongarch@...ts.linux.dev, 
	linux-sh@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-rpi-kernel@...ts.infradead.org, linux-omap@...r.kernel.org, 
	linux-tegra@...r.kernel.org, Stefan Wahren <wahrenst@....net>, 
	Thierry Reding <treding@...dia.com>, soc@...ts.linux.dev
Subject: Re: [PATCH v4 4/4] arm: defconfig: drop RT_GROUP_SCHED=y from bcm2835/tegra/omap2plus

On Fri, Mar 7, 2025 at 3:19 AM Thierry Reding <thierry.reding@...il.com> wrote:
>
> On Wed, Jan 15, 2025 at 04:41:23AM +0800, Celeste Liu wrote:
> > Commit 673ce00c5d6c ("ARM: omap2plus_defconfig: Add support for distros
> > with systemd") said it's because of recommendation from systemd. But
> > systemd changed their recommendation later.[1]
> >
> > For cgroup v1, if turned on, and there's any cgroup in the "cpu" hierarchy it
> > needs an RT budget assigned, otherwise the processes in it will not be able to
> > get RT at all. The problem with RT group scheduling is that it requires the
> > budget assigned but there's no way we could assign a default budget, since the
> > values to assign are both upper and lower time limits, are absolute, and need to
> > be sum up to < 1 for each individal cgroup. That means we cannot really come up
> > with values that would work by default in the general case.[2]
> >
> > For cgroup v2, it's almost unusable as well. If it turned on, the cpu controller
> > can only be enabled when all RT processes are in the root cgroup. But it will
> > lose the benefits of cgroup v2 if all RT process were placed in the same cgroup.
> >
> > Red Hat, Gentoo, Arch Linux and Debian all disable it. systemd also doesn't
> > support it.
> >
> > [1]: https://github.com/systemd/systemd/commit/f4e74be1856b3ac058acbf1be321c31d5299f69f
> > [2]: https://bugzilla.redhat.com/show_bug.cgi?id=1229700
> >
> > Tested-by: Stefan Wahren <wahrenst@....net>
> > Acked-by: Kevin Hilman <khilman@...libre.com>
> > Acked-by: Thierry Reding <treding@...dia.com>
> > Signed-off-by: Celeste Liu <uwu@...lacanthus.name>
> > ---
> >  arch/arm/configs/bcm2835_defconfig   | 1 -
> >  arch/arm/configs/omap2plus_defconfig | 1 -
> >  arch/arm/configs/tegra_defconfig     | 1 -
> >  3 files changed, 3 deletions(-)
>
> Hi Arnd,
>
> is this something that you could pick up? I think so far only the RISC-V
> patch was picked up, but nobody seems to feel responsible for the ARM
> patch here.
I will take the LoongArch patch, but may be squashed to another one
about config file update.

Huacai

>
> Thierry