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Viacheslav Bocharov efecde8a25 gpio: shared-proxy: always serialize with a sleeping mutex
The shared GPIO descriptor used either a mutex or a spinlock, chosen at
runtime from the underlying chip's can_sleep:

	shared_desc->can_sleep = gpiod_cansleep(shared_desc->desc);
	... if (can_sleep) mutex_lock(); else spin_lock_irqsave();

can_sleep describes only the value path (->get/->set). Under the same
lock, however, the proxy may call gpiod_set_config() and
gpiod_direction_*(), which can reach pinctrl paths that take a mutex
(e.g. gpiod_set_config() -> gpiochip_generic_config() ->
pinctrl_gpio_set_config()), independent of can_sleep. On a controller
with non-sleeping MMIO value ops the descriptor lock was a spinlock, so
the sleeping pinctrl call ran from atomic context. Reproduced on an
Amlogic A113X board with the workaround from commit 28f2406838
("pinctrl: meson: mark the GPIO controller as sleeping") reverted; the
original Khadas VIM3 report hit the same path:

	BUG: sleeping function called from invalid context
	  __mutex_lock
	  pinctrl_get_device_gpio_range
	  pinctrl_gpio_set_config
	  gpiochip_generic_config
	  gpiod_set_config
	  gpio_shared_proxy_set_config   <- voting spinlock held
	  ...
	  mmc_pwrseq_simple_probe

The spinlock existed to take the value vote from atomic context, but the
vote and the (possibly sleeping) control operations share the same state
and lock, so this scheme cannot serialize config under a mutex and still
offer atomic value access. Always serialize the shared descriptor with a
mutex instead and mark the proxy a sleeping gpiochip, driving the
underlying GPIO through the cansleep value accessors: those are valid
for both sleeping and non-sleeping chips, so value access keeps working
on fast controllers, at the cost of no longer being atomic.

With every vote edge now driven through the cansleep value setter,
gpio_shared_proxy_set_unlocked() no longer needs a per-call setter: drop
its set_func callback and call gpiod_set_value_cansleep() directly. The
shared direction_output path reaches it only once the line is already an
output, so driving the value there is equivalent to re-issuing
gpiod_direction_output(), without the redundant per-edge re-assertion of
drive config and bias.

This is observable: consumers gating on gpiod_cansleep() take their
sleeping branch on a proxied GPIO (mmc-pwrseq-emmc skips its
emergency-restart reset handler; its normal reset is unaffected), and
consumers that reject sleeping GPIOs (pwm-gpio, ps2-gpio, ...) would
fail to probe. Such atomic users do not share a pin through the proxy,
whose purpose is voting on shared reset/enable lines. The same narrowing
already applies on Amlogic since that workaround, and rockchip
addressed the identical splat per-driver in commit 7ca497be00 ("gpio:
rockchip: Stop calling pinctrl for set_direction"); fixing the proxy
addresses the locking error once, for every controller.

The lock type was added by commit a060b8c511 ("gpiolib: implement
low-level, shared GPIO support"); the sleeping call under it arrived with
the proxy driver.

Fixes: e992d54c6f ("gpio: shared-proxy: implement the shared GPIO proxy driver")
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Closes: https://lore.kernel.org/all/00107523-7737-4b92-a785-14ce4e93b8cb@samsung.com/
Signed-off-by: Viacheslav Bocharov <v@baodeep.com>
Link: https://patch.msgid.link/20260630101545.800625-2-v@baodeep.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
2026-06-30 16:01:28 +02:00
arch LoongArch changes for v7.2 2026-06-26 08:42:49 -07:00
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 mm.git review status for mm-hotfixes-stable..mm-nonmm-stable 2026-06-21 13:20:19 -07:00
Documentation RTC for 7.2 2026-06-27 11:00:18 -07:00
drivers gpio: shared-proxy: always serialize with a sleeping mutex 2026-06-30 16:01:28 +02:00
fs fscrypt fixes for 7.2 2026-06-27 09:20:16 -07:00
include NTB updates include an EPF bug fix to prevent an invalid unmap during 2026-06-28 07:46:12 -07:00
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 Misc fixes: 2026-06-23 16:05:54 -07:00
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
.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
COPYING
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 Including fixes from netfilter and IPsec. 2026-06-25 12:25:36 -07:00
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