From: Dmitry Osipenko <digetx@gmail.com>
To: "Michał Mirosław" <mirq-linux@rere.qmqm.pl>
Cc: Thierry Reding <thierry.reding@gmail.com>,
Jonathan Hunter <jonathanh@nvidia.com>,
Russell King <linux@armlinux.org.uk>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>, Guo Ren <guoren@kernel.org>,
Geert Uytterhoeven <geert@linux-m68k.org>,
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"K . C . Kuen-Chern Lin" <kclin@andestech.com>,
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linux-tegra@vger.kernel.org
Subject: Re: [PATCH v4 05/25] reboot: Warn if restart handler has duplicated priority
Date: Mon, 29 Nov 2021 00:06:19 +0300 [thread overview]
Message-ID: <033ddf2a-6223-1a82-ec64-30f17c891f67@gmail.com> (raw)
In-Reply-To: <YaLNOJTM+lVq+YNS@qmqm.qmqm.pl>
28.11.2021 03:28, Michał Mirosław пишет:
> On Fri, Nov 26, 2021 at 09:00:41PM +0300, Dmitry Osipenko wrote:
>> Add sanity check which ensures that there are no two restart handlers
>> registered with the same priority. Normally it's a direct sign of a
>> problem if two handlers use the same priority.
>
> The patch doesn't ensure the property that there are no duplicated-priority
> entries on the chain.
It's not the exact point of this patch.
> I'd rather see a atomic_notifier_chain_register_unique() that returns
> -EBUSY or something istead of adding an entry with duplicate priority.
> That way it would need only one list traversal unless you want to
> register the duplicate anyway (then you would call the older
> atomic_notifier_chain_register() after reporting the error).
The point of this patch is to warn developers about the problem that
needs to be fixed. We already have such troubling drivers in mainline.
It's not critical to register different handlers with a duplicated
priorities, but such cases really need to be corrected. We shouldn't
break users' machines during transition to the new API, meanwhile
developers should take action of fixing theirs drivers.
> (Or you could return > 0 when a duplicate is registered in
> atomic_notifier_chain_register() if the callers are prepared
> for that. I don't really like this way, though.)
I had a similar thought at some point before and decided that I'm not in
favor of this approach. It's nicer to have a dedicated function that
verifies the uniqueness, IMO.
next prev parent reply other threads:[~2021-11-28 21:08 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-26 18:00 [PATCH v4 00/25] Introduce power-off+restart call chain API Dmitry Osipenko
2021-11-26 18:00 ` [PATCH v4 01/25] notifier: Remove extern annotation from function prototypes Dmitry Osipenko
2021-11-26 18:00 ` [PATCH v4 02/25] notifier: Add blocking_notifier_call_chain_is_empty() Dmitry Osipenko
2021-12-10 18:14 ` Rafael J. Wysocki
2021-12-10 18:19 ` Dmitry Osipenko
2021-11-26 18:00 ` [PATCH v4 03/25] notifier: Add atomic/blocking_notifier_has_unique_priority() Dmitry Osipenko
2021-12-10 18:19 ` Rafael J. Wysocki
2021-12-10 18:52 ` Dmitry Osipenko
2021-12-10 19:05 ` Rafael J. Wysocki
2021-12-10 19:33 ` Dmitry Osipenko
2021-12-10 20:16 ` Dmitry Osipenko
2021-11-26 18:00 ` [PATCH v4 04/25] reboot: Correct typo in a comment Dmitry Osipenko
2021-12-10 18:21 ` Rafael J. Wysocki
2021-11-26 18:00 ` [PATCH v4 05/25] reboot: Warn if restart handler has duplicated priority Dmitry Osipenko
2021-11-28 0:28 ` Michał Mirosław
2021-11-28 21:06 ` Dmitry Osipenko [this message]
2021-11-29 0:26 ` Michał Mirosław
2021-11-29 11:34 ` Dmitry Osipenko
2021-12-10 18:27 ` Rafael J. Wysocki
2021-12-10 19:04 ` Dmitry Osipenko
2021-12-10 19:14 ` Rafael J. Wysocki
2021-12-10 19:42 ` Dmitry Osipenko
2021-12-10 19:44 ` Dmitry Osipenko
2021-12-10 19:49 ` Dmitry Osipenko
2021-12-13 9:23 ` Geert Uytterhoeven
2021-11-26 18:00 ` [PATCH v4 06/25] reboot: Warn if unregister_restart_handler() fails Dmitry Osipenko
2021-12-10 18:32 ` Rafael J. Wysocki
2021-12-10 18:54 ` Dmitry Osipenko
2021-12-10 19:08 ` Rafael J. Wysocki
2021-12-10 19:38 ` Dmitry Osipenko
2021-11-26 18:00 ` [PATCH v4 07/25] reboot: Remove extern annotation from function prototypes Dmitry Osipenko
2021-12-10 18:09 ` Rafael J. Wysocki
2021-12-10 18:15 ` Dmitry Osipenko
2021-12-10 18:35 ` Rafael J. Wysocki
2021-12-10 18:56 ` Dmitry Osipenko
2021-11-26 18:00 ` [PATCH v4 08/25] kernel: Add combined power-off+restart handler call chain API Dmitry Osipenko
2021-11-28 0:43 ` Michał Mirosław
2021-11-28 21:04 ` Dmitry Osipenko
2021-11-28 21:17 ` Michał Mirosław
2021-11-28 21:53 ` Dmitry Osipenko
2021-11-29 0:36 ` Michał Mirosław
2021-11-29 11:52 ` Dmitry Osipenko
2021-11-26 18:00 ` [PATCH v4 09/25] ARM: Use do_kernel_power_off() Dmitry Osipenko
2021-11-26 18:00 ` [PATCH v4 10/25] csky: " Dmitry Osipenko
2021-11-26 18:00 ` [PATCH v4 11/25] riscv: " Dmitry Osipenko
2021-11-26 18:00 ` [PATCH v4 12/25] arm64: " Dmitry Osipenko
2021-11-26 18:00 ` [PATCH v4 13/25] parisc: " Dmitry Osipenko
2021-11-26 18:00 ` [PATCH v4 14/25] xen/x86: " Dmitry Osipenko
2021-11-26 18:00 ` [PATCH v4 15/25] powerpc: " Dmitry Osipenko
2021-11-26 18:00 ` [PATCH v4 16/25] m68k: Switch to new sys-off handler API Dmitry Osipenko
2021-11-26 18:00 ` [PATCH v4 17/25] sh: Use do_kernel_power_off() Dmitry Osipenko
2021-11-26 18:00 ` [PATCH v4 18/25] x86: " Dmitry Osipenko
2021-11-28 1:15 ` Michał Mirosław
2021-11-28 21:06 ` Dmitry Osipenko
2021-11-26 18:00 ` [PATCH v4 19/25] ia64: " Dmitry Osipenko
2021-11-26 18:00 ` [PATCH v4 20/25] mips: " Dmitry Osipenko
2021-11-26 18:00 ` [PATCH v4 21/25] nds32: " Dmitry Osipenko
2021-11-26 18:00 ` [PATCH v4 22/25] memory: emif: Use kernel_can_power_off() Dmitry Osipenko
2021-11-28 1:23 ` Michał Mirosław
2021-11-28 21:04 ` Dmitry Osipenko
2021-11-26 18:00 ` [PATCH v4 23/25] ACPI: power: Switch to sys-off handler API Dmitry Osipenko
2021-11-26 18:01 ` [PATCH v4 24/25] regulator: pfuze100: Use devm_register_sys_off_handler() Dmitry Osipenko
2021-11-26 18:01 ` [PATCH v4 25/25] reboot: Remove pm_power_off_prepare() Dmitry Osipenko
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