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Thomas Richard (TI) b1c0e12097 hwrng: core - Stop/start hwrng_fillfn() kthread before/after suspend-resume
The hwrng_fillfn() kernel thread accesses the RNG device directly. During
suspend and resume sequences, hwrng_fillfn() may attempt to access the RNG
device while it is suspended. To address this, the hwrng_fillfn() kernel
thread is stopped before suspend, and restarted after resume. This is done
using the pm_notifier mechanism.

Issue was found while doing suspend-to-ram on J721S2 EVM board with
omap-rng driver.

echo mem > /sys/power/state
[   27.922259] PM: suspend entry (deep)
[   27.927191] Filesystems sync: 0.000 seconds
[   27.933858] Freezing user space processes
[   27.939119] Freezing user space processes completed (elapsed 0.001 seconds)
[   27.946090] OOM killer disabled.
[   27.949315] Freezing remaining freezable tasks
[   27.954887] Freezing remaining freezable tasks completed (elapsed 0.001 seconds)
[   27.963337] GFP mask restricted
[   27.967069] omap_rng 4e10000.rng: PM: calling platform_pm_suspend @ 195, parent: 4e00000.crypto
[   27.967072] mmcblk mmc1:9fb0: PM: calling mmc_bus_suspend @ 122, parent: mmc1
[   27.968636] mmcblk mmc1:9fb0: PM: mmc_bus_suspend returned 0 after 1546 usecs
[   27.975778] omap_rng 4e10000.rng: PM: platform_pm_suspend returned 0 after 3 usecs
...
[   33.510667] ti-sci 44083000.system-controller: PM: ti_sci_suspend_noirq returned 0 after 0 usecs
[   33.510671] SError Interrupt on CPU0, code 0x00000000bf000000 -- SError
[   33.510681] CPU: 0 UID: 0 PID: 132 Comm: hwrng Tainted: G   M    W           7.0.0-12695-g8923b7a6e11d #19 PREEMPT
[   33.510690] Tainted: [M]=MACHINE_CHECK, [W]=WARN
[   33.510693] Hardware name: Texas Instruments J721S2 EVM (DT)
[   33.510697] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[   33.510701] pc : omap_rng_do_read+0x3c/0xe0
[   33.510709] lr : omap_rng_do_read+0x58/0xe0
[   33.510712] sp : ffff80008942be00
[   33.510713] x29: ffff80008942be00 x28: 0000000000000000 x27: 0000000000000000
[   33.510719] x26: 0000000000000010 x25: 0000000000000010 x24: ffff0008065644e8
[   33.510724] x23: ffff8000878b3370 x22: ffff00080148b2c0 x21: 0000000000000000
[   33.510728] x20: ffff000806564480 x19: 0000000000000064 x18: 0000000000000000
[   33.510732] x17: 6573752031207265 x16: 7466612030206465 x15: 6e72757465722071
[   33.510737] x14: ffff0008062c8080 x13: 000031702bc0da42 x12: 0000000000000001
[   33.510741] x11: 00000000000000c0 x10: 0000000000000b30 x9 : ffff80008942bc80
[   33.510745] x8 : ffff0008062c8b90 x7 : ffff000b7dfa34c0 x6 : 0000000805ca16c1
[   33.510749] x5 : 0000000000000000 x4 : ffff800080e17bfc x3 : ffff800087389c68
[   33.510753] x2 : 0000000000000000 x1 : 0000000000000010 x0 : 000000000000a7c6
[   33.510759] Kernel panic - not syncing: Asynchronous SError Interrupt
[   33.510762] CPU: 0 UID: 0 PID: 132 Comm: hwrng Tainted: G   M    W           7.0.0-12695-g8923b7a6e11d #19 PREEMPT
[   33.510767] Tainted: [M]=MACHINE_CHECK, [W]=WARN
[   33.510768] Hardware name: Texas Instruments J721S2 EVM (DT)
[   33.510770] Call trace:
[   33.510772]  show_stack+0x18/0x24 (C)
[   33.510780]  dump_stack_lvl+0x34/0x8c
[   33.510788]  dump_stack+0x18/0x24
[   33.510792]  vpanic+0x47c/0x4dc
[   33.510799]  do_panic_on_target_cpu+0x0/0x1c
[   33.510803]  add_taint+0x0/0xbc
[   33.510807]  arm64_serror_panic+0x70/0x80
[   33.510812]  do_serror+0x3c/0x70
[   33.510815]  el1h_64_error_handler+0x34/0x50
[   33.510823]  el1h_64_error+0x6c/0x70
[   33.510827]  omap_rng_do_read+0x3c/0xe0 (P)
[   33.510831]  hwrng_fillfn+0x98/0x330
[   33.510834]  kthread+0x130/0x13c
[   33.510845]  ret_from_fork+0x10/0x20
[   33.510850] SMP: stopping secondary CPUs
[   33.519442] Kernel Offset: disabled
[   33.519444] CPU features: 0x04000000,800a0008,00040001,0400421b
[   33.519448] Memory Limit: none
[   33.732904] ---[ end Kernel panic - not syncing: Asynchronous SError Interrupt ]---

Signed-off-by: Thomas Richard (TI) <thomas.richard@bootlin.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
History 2026-08-15 11:24:10 +10:00
arch crypto: qce - Mark QCE as BROKEN 2026-07-17 18:09:22 +10:00
block block: handle REQ_OP_ZONE_APPEND in __bio_integrity_action 2026-06-24 06:53:25 -06:00
certs treewide: fix indentation and whitespace in Kconfig files 2026-05-28 21:24:42 -07:00
crypto crypto: krb5 - use kfree_sensitive() for derived key buffers 2026-08-15 11:24:10 +10:00
Documentation dt-bindings: crypto: qcom,inline-crypto-engine: Add x1e80100 support 2026-08-10 18:20:20 +10:00
drivers
fs fscrypt fixes for 7.2 2026-06-27 09:20:16 -07:00
include crypto: af_alg - Replace 'bool privileged' with flags 2026-08-10 18:34:21 +10:00
init mm.git review status for mm-hotfixes-stable..mm-nonmm-stable 2026-06-21 13:20:19 -07:00
io_uring io_uring-7.2-20260625 2026-06-25 09:53:31 -07:00
ipc kernel-7.2-rc1.misc 2026-06-15 03:05:50 +05:30
kernel Power management fixes for 7.2-rc1 2026-06-26 13:14:18 -07:00
lib Merge git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2026-07-31 17:28:24 +10:00
LICENSES LICENSES: Add modern form of the LGPL-2.1 tags to the usage guide section 2025-10-22 07:58:19 +02:00
mm block-7.2-20260625 2026-06-25 09:56:47 -07:00
net bpf-fixes 2026-06-25 14:09:26 -07:00
rust Rust changes for v7.2 (addendum) 2026-06-24 15:11:08 -07:00
samples Char/Misc/IIO/FPGA/GPIB/etc driver updates for 7.2-rc1 2026-06-22 12:20:21 -07:00
scripts Second round of Kbuild changes for 7.2 2026-06-25 09:06:12 -07:00
security * add Georgia Garcia as co-maintainer of apparmor 2026-06-24 12:33:40 -07:00
sound sound fixes for 7.2-rc1 2026-06-27 12:15:23 -07:00
tools LoongArch changes for v7.2 2026-06-26 08:42:49 -07:00
usr kbuild: uapi: also test UAPI headers against C++ compilers 2026-03-25 13:24:42 +01:00
virt s390: 2026-06-25 10:21:13 -07:00
.clang-format clang-format: fix formatting of guard() and scoped_guard() statements 2026-05-28 21:24:41 -07:00
.clippy.toml rust: bump Clippy's MSRV and clean incompatible_msrv allows 2026-04-07 09:51:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig editorconfig: add rst extension 2026-01-26 19:07:09 -08:00
.get_maintainer.ignore .get_maintainer.ignore: add myself 2026-04-02 16:48:25 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore SPDX patches for 7.2-rc1 2026-06-22 12:06:22 -07:00
.mailmap Including fixes from netfilter and IPsec. 2026-06-25 12:25:36 -07:00
.pylintrc docs: Move the python libraries to tools/lib/python 2025-11-18 09:22:40 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS mm.git review status for mm-hotfixes-stable..mm-nonmm-stable 2026-06-21 13:20:19 -07:00
Kbuild checksyscalls: move instance functionality into generic code 2026-04-05 09:21:32 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS MAINTAINERS: update hisilicon zip driver maintainer 2026-07-05 13:22:36 +08:00
Makefile Linux 7.2-rc1 2026-06-28 12:01:31 -07:00
README docs: add AI Coding Assistants documentation 2026-01-06 14:55:06 -07:00

Linux kernel
============

The Linux kernel is the core of any Linux operating system. It manages hardware,
system resources, and provides the fundamental services for all other software.

Quick Start
-----------

* Report a bug: See Documentation/admin-guide/reporting-issues.rst
* Get the latest kernel: https://kernel.org
* Build the kernel: See Documentation/admin-guide/quickly-build-trimmed-linux.rst
* Join the community: https://lore.kernel.org/

Essential Documentation
-----------------------

All users should be familiar with:

* Building requirements: Documentation/process/changes.rst
* Code of Conduct: Documentation/process/code-of-conduct.rst
* License: See COPYING

Documentation can be built with make htmldocs or viewed online at:
https://www.kernel.org/doc/html/latest/


Who Are You?
============

Find your role below:

* New Kernel Developer - Getting started with kernel development
* Academic Researcher - Studying kernel internals and architecture
* Security Expert - Hardening and vulnerability analysis
* Backport/Maintenance Engineer - Maintaining stable kernels
* System Administrator - Configuring and troubleshooting
* Maintainer - Leading subsystems and reviewing patches
* Hardware Vendor - Writing drivers for new hardware
* Distribution Maintainer - Packaging kernels for distros
* AI Coding Assistant - LLMs and AI-powered development tools


For Specific Users
==================

New Kernel Developer
--------------------

Welcome! Start your kernel development journey here:

* Getting Started: Documentation/process/development-process.rst
* Your First Patch: Documentation/process/submitting-patches.rst
* Coding Style: Documentation/process/coding-style.rst
* Build System: Documentation/kbuild/index.rst
* Development Tools: Documentation/dev-tools/index.rst
* Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst
* Core APIs: Documentation/core-api/index.rst

Academic Researcher
-------------------

Explore the kernel's architecture and internals:

* Researcher Guidelines: Documentation/process/researcher-guidelines.rst
* Memory Management: Documentation/mm/index.rst
* Scheduler: Documentation/scheduler/index.rst
* Networking Stack: Documentation/networking/index.rst
* Filesystems: Documentation/filesystems/index.rst
* RCU (Read-Copy Update): Documentation/RCU/index.rst
* Locking Primitives: Documentation/locking/index.rst
* Power Management: Documentation/power/index.rst

Security Expert
---------------

Security documentation and hardening guides:

* Security Documentation: Documentation/security/index.rst
* LSM Development: Documentation/security/lsm-development.rst
* Self Protection: Documentation/security/self-protection.rst
* Reporting Vulnerabilities: Documentation/process/security-bugs.rst
* CVE Procedures: Documentation/process/cve.rst
* Embargoed Hardware Issues: Documentation/process/embargoed-hardware-issues.rst
* Security Features: Documentation/userspace-api/seccomp_filter.rst

Backport/Maintenance Engineer
-----------------------------

Maintain and stabilize kernel versions:

* Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst
* Backporting Guide: Documentation/process/backporting.rst
* Applying Patches: Documentation/process/applying-patches.rst
* Subsystem Profile: Documentation/maintainer/maintainer-entry-profile.rst
* Git for Maintainers: Documentation/maintainer/configure-git.rst

System Administrator
--------------------

Configure, tune, and troubleshoot Linux systems:

* Admin Guide: Documentation/admin-guide/index.rst
* Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst
* Sysctl Tuning: Documentation/admin-guide/sysctl/index.rst
* Tracing/Debugging: Documentation/trace/index.rst
* Performance Security: Documentation/admin-guide/perf-security.rst
* Hardware Monitoring: Documentation/hwmon/index.rst

Maintainer
----------

Lead kernel subsystems and manage contributions:

* Maintainer Handbook: Documentation/maintainer/index.rst
* Pull Requests: Documentation/maintainer/pull-requests.rst
* Managing Patches: Documentation/maintainer/modifying-patches.rst
* Rebasing and Merging: Documentation/maintainer/rebasing-and-merging.rst
* Development Process: Documentation/process/maintainer-handbooks.rst
* Maintainer Entry Profile: Documentation/maintainer/maintainer-entry-profile.rst
* Git Configuration: Documentation/maintainer/configure-git.rst

Hardware Vendor
---------------

Write drivers and support new hardware:

* Driver API Guide: Documentation/driver-api/index.rst
* Driver Model: Documentation/driver-api/driver-model/driver.rst
* Device Drivers: Documentation/driver-api/infrastructure.rst
* Bus Types: Documentation/driver-api/driver-model/bus.rst
* Device Tree Bindings: Documentation/devicetree/bindings/
* Power Management: Documentation/driver-api/pm/index.rst
* DMA API: Documentation/core-api/dma-api.rst

Distribution Maintainer
-----------------------

Package and distribute the kernel:

* Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst
* ABI Documentation: Documentation/ABI/README
* Kernel Configuration: Documentation/kbuild/kconfig.rst
* Module Signing: Documentation/admin-guide/module-signing.rst
* Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst
* Tainted Kernels: Documentation/admin-guide/tainted-kernels.rst

AI Coding Assistant
-------------------

CRITICAL: If you are an LLM or AI-powered coding assistant, you MUST read and
follow the AI coding assistants documentation before contributing to the Linux
kernel:

* Documentation/process/coding-assistants.rst

This documentation contains essential requirements about licensing, attribution,
and the Developer Certificate of Origin that all AI tools must comply with.


Communication and Support
=========================

* Mailing Lists: https://lore.kernel.org/
* IRC: #kernelnewbies on irc.oftc.net
* Bugzilla: https://bugzilla.kernel.org/
* MAINTAINERS file: Lists subsystem maintainers and mailing lists
* Email Clients: Documentation/process/email-clients.rst