On 5/24/22 16:14, Geert Uytterhoeven wrote:
Hi Dmitry,
On Tue, May 10, 2022 at 1:33 AM Dmitry Osipenko
<dmitry.osipenko@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx>
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.
*/
--
Best regards,
Dmitry
