linux-kernel - Re: [PATCH v4 08/25] kernel: Add combined power-off+restart handler call chain API

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]

Date:   Mon, 29 Nov 2021 00:04:01 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Michał Mirosław <mirq-linux@...e.qmqm.pl>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Guo Ren <guoren@...nel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Greg Ungerer <gerg@...ux-m68k.org>,
        Joshua Thompson <funaho@...ai.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Sebastian Reichel <sre@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Greentime Hu <green.hu@...il.com>,
        Vincent Chen <deanbo422@...il.com>,
        "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
        Helge Deller <deller@....de>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>, Pavel Machek <pavel@....cz>,
        Lee Jones <lee.jones@...aro.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Ulf Hansson <ulf.hansson@...aro.org>, alankao@...estech.com,
        "K . C . Kuen-Chern Lin" <kclin@...estech.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-csky@...r.kernel.org, linux-ia64@...r.kernel.org,
        linux-m68k@...ts.linux-m68k.org, linux-mips@...r.kernel.org,
        linux-parisc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-riscv@...ts.infradead.org, linux-sh@...r.kernel.org,
        xen-devel@...ts.xenproject.org, linux-acpi@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-tegra@...r.kernel.org
Subject: Re: [PATCH v4 08/25] kernel: Add combined power-off+restart handler
 call chain API

28.11.2021 03:43, Michał Mirosław пишет:
> On Fri, Nov 26, 2021 at 09:00:44PM +0300, Dmitry Osipenko wrote:
>> SoC platforms often have multiple ways of how to perform system's
>> power-off and restart operations. Meanwhile today's kernel is limited to
>> a single option. Add combined power-off+restart handler call chain API,
>> which is inspired by the restart API. The new API provides both power-off
>> and restart functionality.
>>
>> The old pm_power_off method will be kept around till all users are
>> converted to the new API.
>>
>> Current restart API will be replaced by the new unified API since
>> new API is its superset. The restart functionality of the sys-off handler
>> API is built upon the existing restart-notifier APIs.
>>
>> In order to ease conversion to the new API, convenient helpers are added
>> for the common use-cases. They will reduce amount of boilerplate code and
>> remove global variables. These helpers preserve old behaviour for cases
>> where only one power-off handler is expected, this is what all existing
>> drivers want, and thus, they could be easily converted to the new API.
>> Users of the new API should explicitly enable power-off chaining by
>> setting corresponding flag of the power_handler structure.
> [...]
> 
> Hi,
> 
> A general question: do we really need three distinct chains for this?

Hello Michał,

At minimum this makes code easier to follow.

> Can't there be only one that chain of callbacks that get a stage
> (RESTART_PREPARE, RESTART, POWER_OFF_PREPARE, POWER_OFF) and can ignore
> them at will? Calling through POWER_OFF_PREPARE would also return
> whether that POWER_OFF is possible (for kernel_can_power_off()).

I'm having trouble with parsing this comment. Could you please try to
rephrase it? I don't see how you could check whether power-off handler
is available if you'll mix all handlers together.

> I would also split this patch into preparation cleanups (like wrapping
> pm_power_off call with a function) and adding the notifier-based
> implementation.

What's the benefit of this split up will be? Are you suggesting that it
will ease reviewing of this patch or something else?