---
title: "Reboot and power-off"
canonical_url: https://developer.repebble.com/pebbleos/docs/kernel/reboot/
last_updated: 2026-11-03
sdk_version: 4.33.1
---
# Reboot and power-off

Source: https://developer.repebble.com/pebbleos/docs/kernel/reboot/

`pbl/kernel/reboot.h` restarts or powers off the system:

- `pbl_reboot()` restarts in order;

- `pbl_power_off()` powers off in order, and restarts if that fails;

- `pbl_reboot_emergency()` resets at once, for contexts where nothing else can be trusted, e.g. a fault handler or the reset-buttons back door.

Code that must shut down before the system goes away registers a handler with `PBL_SYS_OFF_HANDLER_DEFINE()`, for one of four modes:

| 

Mode

 | 

Runs

 | 

Role

 |
| --- | --- | --- |
| 

`PBL_SYS_OFF_RESTART_PREPARE`

 | 

before a restart

 | 

shut down, may block

 |
| 

`PBL_SYS_OFF_POWER_OFF_PREPARE`

 | 

before a power-off

 | 

shut down, may block

 |
| 

`PBL_SYS_OFF_RESTART`

 | 

after the prepare handlers

 | 

restart the system

 |
| 

`PBL_SYS_OFF_POWER_OFF`

 | 

after the prepare handlers

 | 

power off the system

 |

Handlers of a mode run highest priority first. A restart or power-off handler that returns has declined or failed, and the next one runs; once none is left, the kernel resets the SoC.

Prepare handlers only run on the first request, made from a thread with interrupts and the scheduler unlocked. A request from an interrupt, with interrupts locked or from within a handler skips them and goes straight to the restart or power-off handlers, which therefore run in the context of the request and must check it before blocking.

The final reset is the SoC’s `pbl_soc_reset()` when it selects `CONFIG_SOC_HAS_RESET`, e.g. SF32LB52 resets through its PMU and the POSIX host restarts the process; otherwise the architecture’s, the NVIC system reset on Cortex-M.

The firmware’s handlers:

| 

Handler

 | 

Mode

 | 

Priority

 |
| --- | --- | --- |
| 

services to `RunLevel_BareMinimum` (Bluetooth off)

 | 

prepare

 | 

high

 |
| 

PULSE link close

 | 

prepare

 | 

default

 |
| 

wait for flash erases, then hold flash

 | 

prepare

 | 

default

 |
| 

mark the reboot reason as a safe restart

 | 

prepare

 | 

low

 |
| 

core dump after a software failure

 | 

restart

 | 

high

 |
| 

nPM1300 ship mode

 | 

power-off

 | 

default

 |

Reboot reasons and boot bits stay firmware policy: callers set them before calling into the kernel.

Generated from PebbleOS [1dd754433](https://github.com/coredevices/pebbleos/commit/1dd754433b190fee344637b3a6669cb251c611b6). This page is maintained in the pebbleos repository: [docs/kernel/reboot.md](https://github.com/coredevices/pebbleos/blob/1dd754433b190fee344637b3a6669cb251c611b6/docs/kernel/reboot.md).