diff mbox series

[v8,07/27] kernel/reboot: Add kernel_can_power_off()

Message ID 20220509233235.995021-8-dmitry.osipenko@collabora.com (mailing list archive)
State New
Headers show
Series Introduce power-off+restart call chain API | expand

Commit Message

Dmitry Osipenko May 9, 2022, 11:32 p.m. UTC
Add kernel_can_power_off() helper that replaces open-coded checks of
the global pm_power_off variable. This is a necessary step towards
supporting chained power-off handlers.

Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 include/linux/reboot.h |  1 +
 kernel/reboot.c        | 14 +++++++++++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

Comments

Geert Uytterhoeven May 24, 2022, 1:14 p.m. UTC | #1
Hi Dmitry,

On Tue, May 10, 2022 at 1:33 AM Dmitry Osipenko
<dmitry.osipenko@collabora.com> wrote:
> Add kernel_can_power_off() helper that replaces open-coded checks of
> the global pm_power_off variable. This is a necessary step towards
> supporting chained power-off handlers.
>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>

Thanks for your patch, which is now commit 0e2110d2e910e44c
("kernel/reboot: Add kernel_can_power_off()") in pm/linux-next.

This causes the "poweroff" command (Debian nfsroot) to no longer
cleanly halt the system on arm32 systems, but fail with a panic
instead:

-reboot: System halted
+reboot: Power down
+Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000000
+CPU: 0 PID: 1 Comm: systemd-shutdow Not tainted
5.18.0-rc7-shmobile-00007-g0e2110d2e910 #1274
+Hardware name: Generic R-Car Gen2 (Flattened Device Tree)
+ unwind_backtrace from show_stack+0x10/0x14
+ show_stack from dump_stack_lvl+0x40/0x4c
+ dump_stack_lvl from panic+0xf4/0x330
+ panic from do_exit+0x1c8/0x8e4
+ do_exit from __do_sys_reboot+0x174/0x1fc
+ __do_sys_reboot from ret_fast_syscall+0x0/0x54
+Exception stack(0xf0815fa8 to 0xf0815ff0)
+5fa0:                   004e6954 00000000 fee1dead 28121969 4321fedc f0d94600
+5fc0: 004e6954 00000000 00000000 00000058 befa0c78 00000000 befa0c10 004e56f8
+5fe0: 00000058 befa0b6c b6ec8d45 b6e4a746
+---[ end Kernel panic - not syncing: Attempted to kill init!
exitcode=0x00000000 ]---

On arm64, "poweroff" causes a clean "reboot: Power down" before/after.

On both arm32 and arm64, the same handlers are registered:
  - SYS_OFF_MODE_POWER_OFF_PREPARE: legacy_pm_power_off_prepare
  - SYS_OFF_MODE_POWER_OFF: legacy_pm_power_off

On both arm32 and arm64, legacy_pm_power_off_prepare() is called.
On both arm32 and arm64, legacy_pm_power_off() does not seem to
be called.

On arm32, both pm_power_off_prepare and pm_power_off are NULL.
On arm64, pm_power_off_prepare is NULL, and
pm_power_off is psci_sys_poweroff.

Do you have a clue?
Thanks!

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
Dmitry Osipenko May 24, 2022, 1:41 p.m. UTC | #2
On 5/24/22 16:14, Geert Uytterhoeven wrote:
> Hi Dmitry,
> 
> On Tue, May 10, 2022 at 1:33 AM Dmitry Osipenko
> <dmitry.osipenko@collabora.com> wrote:
>> Add kernel_can_power_off() helper that replaces open-coded checks of
>> the global pm_power_off variable. This is a necessary step towards
>> supporting chained power-off handlers.
>>
>> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
> 
> Thanks for your patch, which is now commit 0e2110d2e910e44c
> ("kernel/reboot: Add kernel_can_power_off()") in pm/linux-next.
> 
> This causes the "poweroff" command (Debian nfsroot) to no longer
> cleanly halt the system on arm32 systems, but fail with a panic
> instead:
> 
> -reboot: System halted
> +reboot: Power down
> +Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000000
> +CPU: 0 PID: 1 Comm: systemd-shutdow Not tainted
> 5.18.0-rc7-shmobile-00007-g0e2110d2e910 #1274
> +Hardware name: Generic R-Car Gen2 (Flattened Device Tree)
> + unwind_backtrace from show_stack+0x10/0x14
> + show_stack from dump_stack_lvl+0x40/0x4c
> + dump_stack_lvl from panic+0xf4/0x330
> + panic from do_exit+0x1c8/0x8e4
> + do_exit from __do_sys_reboot+0x174/0x1fc
> + __do_sys_reboot from ret_fast_syscall+0x0/0x54
> +Exception stack(0xf0815fa8 to 0xf0815ff0)
> +5fa0:                   004e6954 00000000 fee1dead 28121969 4321fedc f0d94600
> +5fc0: 004e6954 00000000 00000000 00000058 befa0c78 00000000 befa0c10 004e56f8
> +5fe0: 00000058 befa0b6c b6ec8d45 b6e4a746
> +---[ end Kernel panic - not syncing: Attempted to kill init!
> exitcode=0x00000000 ]---
> 
> On arm64, "poweroff" causes a clean "reboot: Power down" before/after.
> 
> On both arm32 and arm64, the same handlers are registered:
>   - SYS_OFF_MODE_POWER_OFF_PREPARE: legacy_pm_power_off_prepare
>   - SYS_OFF_MODE_POWER_OFF: legacy_pm_power_off
> 
> On both arm32 and arm64, legacy_pm_power_off_prepare() is called.
> On both arm32 and arm64, legacy_pm_power_off() does not seem to
> be called.
> 
> On arm32, both pm_power_off_prepare and pm_power_off are NULL.
> On arm64, pm_power_off_prepare is NULL, and
> pm_power_off is psci_sys_poweroff.
> 
> Do you have a clue?
> Thanks!

Thank you, Geert! I see the problem, the kernel_can_power_off() checks whether power-off handler is registered, but it's always registered because legacy_pm_power_off is registered unconditionally. So it causes trouble for platforms that don't have power-off handler installed at all. All platforms that I tested have a power-off handler, so now wonder that I didn't notice this before.

This change should fix the problem, please give it a try:

--- 8< ---

diff --git a/kernel/reboot.c b/kernel/reboot.c
index 0bdc64ecf4f6..2d55b8bdb444 100644
--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -569,22 +569,6 @@ static int legacy_pm_power_off(struct sys_off_data *data)
 	return NOTIFY_DONE;
 }
 
-/*
- * Register sys-off handlers for legacy PM callbacks. This allows legacy
- * PM callbacks co-exist with the new sys-off API.
- *
- * TODO: Remove legacy handlers once all legacy PM users will be switched
- *       to the sys-off based APIs.
- */
-static int __init legacy_pm_init(void)
-{
-	register_sys_off_handler(SYS_OFF_MODE_POWER_OFF, SYS_OFF_PRIO_DEFAULT,
-				 legacy_pm_power_off, NULL);
-
-	return 0;
-}
-core_initcall(legacy_pm_init);
-
 static void do_kernel_power_off_prepare(void)
 {
 	blocking_notifier_call_chain(&power_off_prep_handler_list, 0, NULL);
@@ -670,6 +654,18 @@ SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
 	if (ret)
 		return ret;
 
+	/*
+	 * Register sys-off handler for the legacy PM callback. This allows
+	 * legacy PM callbacks co-exist with the new sys-off API.
+	 *
+	 * TODO: Remove legacy handler once all legacy PM users will be
+	 *       switched to the sys-off based APIs.
+	 */
+	if (pm_power_off)
+		register_sys_off_handler(SYS_OFF_MODE_POWER_OFF,
+					 SYS_OFF_PRIO_DEFAULT,
+					 legacy_pm_power_off, NULL);
+
 	/* Instead of trying to make the power_off code look like
 	 * halt when pm_power_off is not set do it the easy way.
 	 */
Geert Uytterhoeven May 24, 2022, 3:03 p.m. UTC | #3
Hi Dmitry,

On Tue, May 24, 2022 at 3:41 PM Dmitry Osipenko
<dmitry.osipenko@collabora.com> wrote:
> On 5/24/22 16:14, Geert Uytterhoeven wrote:
> > On Tue, May 10, 2022 at 1:33 AM Dmitry Osipenko
> > <dmitry.osipenko@collabora.com> wrote:
> >> Add kernel_can_power_off() helper that replaces open-coded checks of
> >> the global pm_power_off variable. This is a necessary step towards
> >> supporting chained power-off handlers.
> >>
> >> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
> >
> > Thanks for your patch, which is now commit 0e2110d2e910e44c
> > ("kernel/reboot: Add kernel_can_power_off()") in pm/linux-next.
> >
> > This causes the "poweroff" command (Debian nfsroot) to no longer
> > cleanly halt the system on arm32 systems, but fail with a panic
> > instead:
> >
> > -reboot: System halted
> > +reboot: Power down
> > +Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000000
> > +CPU: 0 PID: 1 Comm: systemd-shutdow Not tainted
> > 5.18.0-rc7-shmobile-00007-g0e2110d2e910 #1274
> > +Hardware name: Generic R-Car Gen2 (Flattened Device Tree)
> > + unwind_backtrace from show_stack+0x10/0x14
> > + show_stack from dump_stack_lvl+0x40/0x4c
> > + dump_stack_lvl from panic+0xf4/0x330
> > + panic from do_exit+0x1c8/0x8e4
> > + do_exit from __do_sys_reboot+0x174/0x1fc
> > + __do_sys_reboot from ret_fast_syscall+0x0/0x54
> > +Exception stack(0xf0815fa8 to 0xf0815ff0)
> > +5fa0:                   004e6954 00000000 fee1dead 28121969 4321fedc f0d94600
> > +5fc0: 004e6954 00000000 00000000 00000058 befa0c78 00000000 befa0c10 004e56f8
> > +5fe0: 00000058 befa0b6c b6ec8d45 b6e4a746
> > +---[ end Kernel panic - not syncing: Attempted to kill init!
> > exitcode=0x00000000 ]---
> >
> > On arm64, "poweroff" causes a clean "reboot: Power down" before/after.
> >
> > On both arm32 and arm64, the same handlers are registered:
> >   - SYS_OFF_MODE_POWER_OFF_PREPARE: legacy_pm_power_off_prepare
> >   - SYS_OFF_MODE_POWER_OFF: legacy_pm_power_off
> >
> > On both arm32 and arm64, legacy_pm_power_off_prepare() is called.
> > On both arm32 and arm64, legacy_pm_power_off() does not seem to
> > be called.
> >
> > On arm32, both pm_power_off_prepare and pm_power_off are NULL.
> > On arm64, pm_power_off_prepare is NULL, and
> > pm_power_off is psci_sys_poweroff.
> >
> > Do you have a clue?
> > Thanks!
>
> Thank you, Geert! I see the problem, the kernel_can_power_off() checks whether power-off handler is registered, but it's always registered because legacy_pm_power_off is registered unconditionally. So it causes trouble for platforms that don't have power-off handler installed at all. All platforms that I tested have a power-off handler, so now wonder that I didn't notice this before.
>
> This change should fix the problem, please give it a try:

Thank you, that fixes the problem for me!

Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
Dmitry Osipenko May 24, 2022, 8:16 p.m. UTC | #4
On 5/24/22 18:03, Geert Uytterhoeven wrote:
> Hi Dmitry,
> 
> On Tue, May 24, 2022 at 3:41 PM Dmitry Osipenko
> <dmitry.osipenko@collabora.com> wrote:
>> On 5/24/22 16:14, Geert Uytterhoeven wrote:
>>> On Tue, May 10, 2022 at 1:33 AM Dmitry Osipenko
>>> <dmitry.osipenko@collabora.com> wrote:
>>>> Add kernel_can_power_off() helper that replaces open-coded checks of
>>>> the global pm_power_off variable. This is a necessary step towards
>>>> supporting chained power-off handlers.
>>>>
>>>> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
>>>
>>> Thanks for your patch, which is now commit 0e2110d2e910e44c
>>> ("kernel/reboot: Add kernel_can_power_off()") in pm/linux-next.
>>>
>>> This causes the "poweroff" command (Debian nfsroot) to no longer
>>> cleanly halt the system on arm32 systems, but fail with a panic
>>> instead:
>>>
>>> -reboot: System halted
>>> +reboot: Power down
>>> +Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000000
>>> +CPU: 0 PID: 1 Comm: systemd-shutdow Not tainted
>>> 5.18.0-rc7-shmobile-00007-g0e2110d2e910 #1274
>>> +Hardware name: Generic R-Car Gen2 (Flattened Device Tree)
>>> + unwind_backtrace from show_stack+0x10/0x14
>>> + show_stack from dump_stack_lvl+0x40/0x4c
>>> + dump_stack_lvl from panic+0xf4/0x330
>>> + panic from do_exit+0x1c8/0x8e4
>>> + do_exit from __do_sys_reboot+0x174/0x1fc
>>> + __do_sys_reboot from ret_fast_syscall+0x0/0x54
>>> +Exception stack(0xf0815fa8 to 0xf0815ff0)
>>> +5fa0:                   004e6954 00000000 fee1dead 28121969 4321fedc f0d94600
>>> +5fc0: 004e6954 00000000 00000000 00000058 befa0c78 00000000 befa0c10 004e56f8
>>> +5fe0: 00000058 befa0b6c b6ec8d45 b6e4a746
>>> +---[ end Kernel panic - not syncing: Attempted to kill init!
>>> exitcode=0x00000000 ]---
>>>
>>> On arm64, "poweroff" causes a clean "reboot: Power down" before/after.
>>>
>>> On both arm32 and arm64, the same handlers are registered:
>>>   - SYS_OFF_MODE_POWER_OFF_PREPARE: legacy_pm_power_off_prepare
>>>   - SYS_OFF_MODE_POWER_OFF: legacy_pm_power_off
>>>
>>> On both arm32 and arm64, legacy_pm_power_off_prepare() is called.
>>> On both arm32 and arm64, legacy_pm_power_off() does not seem to
>>> be called.
>>>
>>> On arm32, both pm_power_off_prepare and pm_power_off are NULL.
>>> On arm64, pm_power_off_prepare is NULL, and
>>> pm_power_off is psci_sys_poweroff.
>>>
>>> Do you have a clue?
>>> Thanks!
>>
>> Thank you, Geert! I see the problem, the kernel_can_power_off() checks whether power-off handler is registered, but it's always registered because legacy_pm_power_off is registered unconditionally. So it causes trouble for platforms that don't have power-off handler installed at all. All platforms that I tested have a power-off handler, so now wonder that I didn't notice this before.
>>
>> This change should fix the problem, please give it a try:
> 
> Thank you, that fixes the problem for me!
> 
> Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>

Great! I'll send the proper patch soon.
diff mbox series

Patch

diff --git a/include/linux/reboot.h b/include/linux/reboot.h
index 6b951d68c0c7..c52f77ee4ddd 100644
--- a/include/linux/reboot.h
+++ b/include/linux/reboot.h
@@ -149,6 +149,7 @@  extern void kernel_restart_prepare(char *cmd);
 extern void kernel_restart(char *cmd);
 extern void kernel_halt(void);
 extern void kernel_power_off(void);
+extern bool kernel_can_power_off(void);
 
 void ctrl_alt_del(void);
 
diff --git a/kernel/reboot.c b/kernel/reboot.c
index eaede35f45e2..982e58c11ce8 100644
--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -523,6 +523,18 @@  void do_kernel_power_off(void)
 	atomic_notifier_call_chain(&power_off_handler_list, 0, NULL);
 }
 
+/**
+ *	kernel_can_power_off - check whether system can be powered off
+ *
+ *	Returns true if power-off handler is registered and system can be
+ *	powered off, false otherwise.
+ */
+bool kernel_can_power_off(void)
+{
+	return !atomic_notifier_call_chain_is_empty(&power_off_handler_list);
+}
+EXPORT_SYMBOL_GPL(kernel_can_power_off);
+
 /**
  *	kernel_power_off - power_off the system
  *
@@ -581,7 +593,7 @@  SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
 	/* Instead of trying to make the power_off code look like
 	 * halt when pm_power_off is not set do it the easy way.
 	 */
-	if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
+	if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !kernel_can_power_off())
 		cmd = LINUX_REBOOT_CMD_HALT;
 
 	mutex_lock(&system_transition_mutex);