RPi5: Kernel fails to boot with CONFIG_INIT_STACK_NONE=y (works with INIT_STACK_ALL_ZERO)

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#7,336 opened on Apr 27, 2026 0 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty: 4/5
Estimated time: 3-5 days
Newbie friendliness: 35/100

Issue type: Bug
Clarity: Needs clarification
Activity status: Quiet
Tech stack: c, linux
Domain: embedded-iot, networking, operating-systems

Research direction

Start by reproducing the failure on Raspberry Pi 5 with rpi-6.12.y, a bcm2712_defconfig-based configuration, clang, and CONFIG_INIT_STACK_NONE=y. Compare the early-boot and networking behavior against CONFIG_INIT_STACK_ALL_ZERO=y; done means the kernel boots and networking works with stack initialization disabled.

Written by the indexing model from the issue text.

Description

Describe the bug

I encountered a configuration-dependent issue on Raspberry Pi 5 related to stack initialization.

When using:

CONFIG_INIT_STACK_NONE=y

the system exhibits failures, while switching to:

CONFIG_INIT_STACK_ALL_ZERO=y

resolves the issue completely.

Tested on:

Raspberry Pi 5
Kernel: rpi-6.12.y (tested on 6.12.79 and 6.12.83)
Toolchain: clang (LLVM)
Custom config derived from bcm2712_defconfig

Behavior:

Kernel 6.12.79:

System does not reach kernel output
No visible logs
Fan remains at high speed (system appears stuck very early in boot)

Kernel 6.12.83:

System boots
Networking does not come up

Switching back to:

CONFIG_INIT_STACK_ALL_ZERO=y

restores full functionality, including networking.

The issue is reproducible by changing only:

CONFIG_INIT_STACK_ALL_ZERO y -> n
CONFIG_INIT_STACK_NONE n -> y

This suggests a possible dependency on implicitly zero-initialized stack data in early boot or platform/network initialization code.

Steps to reproduce the behaviour

Build kernel for Raspberry Pi 5 using rpi-6.12.y
Use a config based on bcm2712_defconfig
Set:

CONFIG_INIT_STACK_NONE=y
Boot system

Result:

Kernel 6.12.79: system hangs very early
Kernel 6.12.83: system boots but networking is not working

Change config to:

CONFIG_INIT_STACK_ALL_ZERO=y
Rebuild and reboot

Result:

System boots correctly
Networking works

Device (s)

Raspberry Pi 5

System

OS: Gentoo-based custom system
Kernel: rpi-6.12.y (6.12.79 and 6.12.83)
Toolchain: clang (LLVM)
Firmware: 2026/02/23 10:01:39
Copyright (c) 2012 Broadcom
version 85353ce4 (release) (embedded)

Logs

No response

Additional context

No response

Dominant language: C
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Merged PRs (30d): 21

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