From: "Rafael J. Wysocki" <rafael@kernel.org>
To: Dmitry Osipenko <digetx@gmail.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
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Subject: Re: [PATCH v4 06/25] reboot: Warn if unregister_restart_handler() fails
Date: Fri, 10 Dec 2021 20:08:21 +0100 [thread overview]
Message-ID: <CAJZ5v0iP_VnNW3ChmdvRFg1gvwvkDGmqtGnf1oVwQxXY303RkQ@mail.gmail.com> (raw)
In-Reply-To: <c518ce36-09d2-16a3-cec2-6bab8260e3cf@gmail.com>
On Fri, Dec 10, 2021 at 7:54 PM Dmitry Osipenko <digetx@gmail.com> wrote:
>
> 10.12.2021 21:32, Rafael J. Wysocki пишет:
> > On Fri, Nov 26, 2021 at 7:02 PM Dmitry Osipenko <digetx@gmail.com> wrote:
> >>
> >> Emit warning if unregister_restart_handler() fails since it never should
> >> fail. This will ease further API development by catching mistakes early.
> >>
> >> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> >> ---
> >> kernel/reboot.c | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/kernel/reboot.c b/kernel/reboot.c
> >> index e6659ae329f1..f0e7b9c13f6b 100644
> >> --- a/kernel/reboot.c
> >> +++ b/kernel/reboot.c
> >> @@ -210,7 +210,7 @@ EXPORT_SYMBOL(register_restart_handler);
> >> */
> >> int unregister_restart_handler(struct notifier_block *nb)
> >> {
> >> - return atomic_notifier_chain_unregister(&restart_handler_list, nb);
> >> + return WARN_ON(atomic_notifier_chain_unregister(&restart_handler_list, nb));
> >
> > The only reason why it can fail is if the object pointed to by nb is
> > not in the chain.
>
> I had exactly this case where object wasn't in the chain due to a bug
> and this warning was very helpful.
During the development. In production it would be rather annoying.
> > Why WARN() about this? And what about systems with
> > panic_on_warn set?
>
> That warning condition will never happen normally, only when something
> is seriously wrong.
>
> Those systems with panic_on_warn will get what was they asked for.
They may not be asking for panicking on bugs in the reboot notifier
code, though. That's what your change is making them panic on.
next prev parent reply other threads:[~2021-12-10 19:08 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
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 [this message]
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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