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Harald Freudenberger 7ecac01cf1 s390/ap: Fix locking issue in SE bind and associate sysfs functions
Revisit and reorganize the locking and lock coverage of the
ap->lock spinlock as used in the two sysfs functions
se_bind_store() and se_associate_store().

A kernel run reported a possible deadlock situation, caused by
holding the spinlock (ap->lock) while triggering a uevent.
The fix rearranges the code protected by the spinlock by excluding
the uevent invocation, which does not require protection.

Additionally, the start of the protected region is moved earlier
to cover more lines, ensuring a consistent view of the AP queue
state between reading and updating its struct fields.

	=====================================================
	WARNING: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected
	7.1.0-20260601.rc6.git12.516b5dbd4d4a.300.fc44.s390x+debug #1 Not tainted
	-----------------------------------------------------
	setupseguest.sh/11034 [HC0[0]:SC0[2]:HE1:SE0] is trying to acquire:
	000001c991f498e8 (fs_reclaim){+.+.}-{0:0}, at: __kmalloc_cache_noprof+0x5a/0x6d0
	and this task is already holding:
	000000c4a1a12378 (&aq->lock){+.-.}-{2:2}, at: se_bind_store+0x96/0x3a0
	which would create a new lock dependency:
	 (&aq->lock){+.-.}-{2:2} -> (fs_reclaim){+.+.}-{0:0}
	but this new dependency connects a SOFTIRQ-irq-safe lock:
	 (&aq->lock){+.-.}-{2:2}
	... which became SOFTIRQ-irq-safe at:
	  __lock_acquire+0x5ae/0x15a0
	  lock_acquire+0x14c/0x400
	  _raw_spin_lock_bh+0x58/0xb0
	  ap_tasklet_fn+0x72/0xd0
	  tasklet_action_common+0x174/0x1b0
	  handle_softirqs+0x180/0x5c0
	  irq_exit_rcu+0x196/0x200
	  do_ext_irq+0x12a/0x4d0
	  ext_int_handler+0xc6/0xf0
	  folio_zero_user+0x1c6/0x240
	  folio_zero_user+0x182/0x240
	  vma_alloc_anon_folio_pmd+0xa0/0x1d0
	  __do_huge_pmd_anonymous_page+0x3a/0x200
	  __handle_mm_fault+0x56c/0x590
	  handle_mm_fault+0xa2/0x370
	  do_exception+0x292/0x590
	  __do_pgm_check+0x136/0x3e0
	  pgm_check_handler+0x114/0x160
	to a SOFTIRQ-irq-unsafe lock:
	 (fs_reclaim){+.+.}-{0:0}
	... which became SOFTIRQ-irq-unsafe at:
	...
	  __lock_acquire+0x5ae/0x15a0
	  lock_acquire+0x14c/0x400
	  __fs_reclaim_acquire+0x44/0x50
	  fs_reclaim_acquire+0xbe/0x100
	  fs_reclaim_correct_nesting+0x20/0x70
	  dotest+0x5e/0x148
	  locking_selftest+0x2854/0x2a88
	  start_kernel+0x3b2/0x4f0
	  startup_continue+0x2e/0x40
	other info that might help us debug this:
	 Possible interrupt unsafe locking scenario:
	       CPU0                    CPU1
	       ----                    ----
	  lock(fs_reclaim);
				       local_irq_disable();
				       lock(&aq->lock);
				       lock(fs_reclaim);
	  <Interrupt>
	    lock(&aq->lock);
	 *** DEADLOCK ***
	4 locks held by setupseguest.sh/11034:
	 #0: 000000c485d01440 (sb_writers#4){.+.+}-{0:0}, at: vfs_write+0x2fc/0x380
	 #1: 000000c4d2283288 (&of->mutex#2){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x12a0x270
	 #2: 000000c4a1830e48 (kn->active#172){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x1e/0x270
	 #3: 000000c4a1a12378 (&aq->lock){+.-.}-{2:2}, at: se_bind_store+0x96/0x3a0
	the dependencies between SOFTIRQ-irq-safe lock and the holding lock:
	-> (&aq->lock){+.-.}-{2:2} {
	   HARDIRQ-ON-W at:
			    __lock_acquire+0x5ae/0x15a0
			    lock_acquire+0x14c/0x400
			    _raw_spin_lock_bh+0x58/0xb0
			    ap_queue_init_state+0x2e/0x50
			    ap_scan_domains+0x5d6/0x620
			    ap_scan_adapter+0x4c0/0x810
			    ap_scan_bus+0x70/0x350
			    ap_scan_bus_wq_callback+0x56/0x80
			    process_one_work+0x2ba/0x820
			    worker_thread+0x21a/0x400
			    kthread+0x164/0x190
			    __ret_from_fork+0x4c/0x340
			    ret_from_fork+0xa/0x30
	   IN-SOFTIRQ-W at:
			    __lock_acquire+0x5ae/0x15a0
			    lock_acquire+0x14c/0x400
			    _raw_spin_lock_bh+0x58/0xb0
			    ap_tasklet_fn+0x72/0xd0
			    tasklet_action_common+0x174/0x1b0
			    handle_softirqs+0x180/0x5c0
			    irq_exit_rcu+0x196/0x200
			    do_ext_irq+0x12a/0x4d0
			    ext_int_handler+0xc6/0xf0
			    folio_zero_user+0x1c6/0x240
			    folio_zero_user+0x182/0x240
			    vma_alloc_anon_folio_pmd+0xa0/0x1d0
			    __do_huge_pmd_anonymous_page+0x3a/0x200
			    __handle_mm_fault+0x56c/0x590
			    handle_mm_fault+0xa2/0x370
			    do_exception+0x292/0x590
			    __do_pgm_check+0x136/0x3e0
			    pgm_check_handler+0x114/0x160
	   INITIAL USE at:
			   __lock_acquire+0x5ae/0x15a0
			   lock_acquire+0x14c/0x400
			   _raw_spin_lock_bh+0x58/0xb0
			   ap_queue_init_state+0x2e/0x50
			   ap_scan_domains+0x5d6/0x620
			   ap_scan_adapter+0x4c0/0x810
			   ap_scan_bus+0x70/0x350
			   ap_scan_bus_wq_callback+0x56/0x80
			   process_one_work+0x2ba/0x820
			   worker_thread+0x21a/0x400
			   kthread+0x164/0x190
			   __ret_from_fork+0x4c/0x340
			   ret_from_fork+0xa/0x30
	 }
	 ... key      at: [<000001c9936e8aa0>] __key.7+0x0/0x10
	the dependencies between the lock to be acquired
	 and SOFTIRQ-irq-unsafe lock:
	-> (fs_reclaim){+.+.}-{0:0} {
	   HARDIRQ-ON-W at:
			    __lock_acquire+0x5ae/0x15a0
			    lock_acquire+0x14c/0x400
			    __fs_reclaim_acquire+0x44/0x50
			    fs_reclaim_acquire+0xbe/0x100
			    fs_reclaim_correct_nesting+0x20/0x70
			    dotest+0x5e/0x148
			    locking_selftest+0x2854/0x2a88
			    start_kernel+0x3b2/0x4f0
			    startup_continue+0x2e/0x40
	   SOFTIRQ-ON-W at:
			    __lock_acquire+0x5ae/0x15a0
			    lock_acquire+0x14c/0x400
			    __fs_reclaim_acquire+0x44/0x50
			    fs_reclaim_acquire+0xbe/0x100
			    fs_reclaim_correct_nesting+0x20/0x70
			    dotest+0x5e/0x148
			    locking_selftest+0x2854/0x2a88
			    start_kernel+0x3b2/0x4f0
			    startup_continue+0x2e/0x40
	   INITIAL USE at:
			   __lock_acquire+0x5ae/0x15a0
			   lock_acquire+0x14c/0x400
			   __fs_reclaim_acquire+0x44/0x50
			   fs_reclaim_acquire+0xbe/0x100
			   fs_reclaim_correct_nesting+0x20/0x70
			   dotest+0x5e/0x148
			   locking_selftest+0x2854/0x2a88
			   start_kernel+0x3b2/0x4f0
			   startup_continue+0x2e/0x40
	 }
	 ... key      at: [<000001c991f498e8>] __fs_reclaim_map+0x0/0x30
	 ... acquired at:
	   check_prev_add+0x178/0xf40
	   __lock_acquire+0x12aa/0x15a0
	   lock_acquire+0x14c/0x400
	   __fs_reclaim_acquire+0x44/0x50
	   fs_reclaim_acquire+0xbe/0x100
	   __kmalloc_cache_noprof+0x5a/0x6d0
	   kobject_uevent_env+0xd4/0x420
	   ap_send_se_bind_uevent+0x48/0x70
	   se_bind_store+0x146/0x3a0
	   kernfs_fop_write_iter+0x18c/0x270
	   vfs_write+0x23c/0x380
	   ksys_write+0x88/0x120
	   __do_syscall+0x170/0x750
	   system_call+0x72/0x90
	stack backtrace:
	CPU: 6 UID: 0 PID: 11034 Comm: setupseguest.sh Not tainted 7.1.0-20260601.rc6.git2.516b5dbd4d4a.300.fc44.s390x+debug #1 PREEMPT
	Hardware name: IBM 9175 ME1 701 (KVM/Linux)
	Call Trace:
	 [<000001c98ffa0a7e>] dump_stack_lvl+0xae/0x108
	 [<000001c9900a6d7a>] print_bad_irq_dependency+0x47a/0x480
	 [<000001c9900a7184>] check_irq_usage+0x404/0x4c0
	 [<000001c9900a73b8>] check_prev_add+0x178/0xf40
	 [<000001c9900aaf1a>] __lock_acquire+0x12aa/0x15a0
	 [<000001c9900ab35c>] lock_acquire+0x14c/0x400
	 [<000001c9903be454>] __fs_reclaim_acquire+0x44/0x50
	 [<000001c9903be51e>] fs_reclaim_acquire+0xbe/0x100
	 [<000001c9903cf4ca>] __kmalloc_cache_noprof+0x5a/0x6d0
	 [<000001c9910ca9d4>] kobject_uevent_env+0xd4/0x420
	 [<000001c990d84098>] ap_send_se_bind_uevent+0x48/0x70
	 [<000001c990d87416>] se_bind_store+0x146/0x3a0
	 [<000001c99057da7c>] kernfs_fop_write_iter+0x18c/0x270
	 [<000001c99047712c>] vfs_write+0x23c/0x380
	 [<000001c990477438>] ksys_write+0x88/0x120
	 [<000001c9910f64e0>] __do_syscall+0x170/0x750
	 [<000001c99110a412>] system_call+0x72/0x90
	INFO: lockdep is turned off.

Fixes: 4179c39842 ("s390/ap: Implement SE bind and associate uevents")
Reported-by: Ingo Franzki <ifranzki@linux.ibm.com>
Suggested-by: Finn Callies <fcallies@linux.ibm.com>
Reviewed-by: Finn Callies <fcallies@linux.ibm.com>
Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
2026-06-09 19:33:00 +02:00
arch s390/percpu: Provide arch_this_cpu_write() implementation 2026-06-03 15:32:47 +02:00
block block: only restrict bio allocation gfp mask asked to block 2026-04-21 11:42:12 -06:00
certs Clang build fixes for 7.1 2026-04-24 09:29:51 -07:00
crypto This push contains the following changes: 2026-05-02 12:31:43 -07:00
Documentation s390/tracing: Add s390-tod clock 2026-05-26 08:15:41 +02:00
drivers s390/ap: Fix locking issue in SE bind and associate sysfs functions 2026-06-09 19:33:00 +02:00
fs Description for this pull request: 2026-05-02 12:25:57 -07:00
include drm fixes for 7.1-rc2 2026-05-01 16:56:08 -07:00
init memblock: updates for 7.0-rc1 2026-04-18 11:29:14 -07:00
io_uring io_uring-7.1-20260430 2026-05-01 11:01:31 -07:00
ipc Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
kernel Fix lockup in requeue-PI during signal/timeout wakeups, 2026-05-03 08:17:09 -07:00
lib 20 hotfixes. All are for MM (and for MMish maintainers). 9 are cc:stable 2026-05-01 08:45:23 -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 slab fixes for 7.1-rc1 2026-05-03 08:19:57 -07:00
net net/sched: cls_flower: revert unintended changes 2026-04-30 13:47:01 +02:00
rust Char/Misc/IIO/and others driver updates for 7.1-rc1 2026-04-24 13:23:50 -07:00
samples soc: drivers for 7.1 2026-04-16 20:34:34 -07:00
scripts First round of Kbuild fixes for 7.1 2026-04-25 17:04:15 -07:00
security selinux: fix avdcache auditing 2026-04-28 18:13:58 -04:00
sound ALSA: hda/tas2781: Fix incorrect bit update for non-book-zero or book 0 pages >1 2026-04-29 07:51:17 +02:00
tools Assorted arm64, ACPI and kselftest fixes for 7.1-rc2: 2026-05-01 16:32:42 -07:00
usr kbuild: uapi: also test UAPI headers against C++ compilers 2026-03-25 13:24:42 +01:00
virt Arm: 2026-04-17 07:18:03 -07:00
.clang-format Devicetree updates for v7.0: 2026-02-11 18:27:08 -08:00
.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 Askar 2026-04-15 02:15:02 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: rust: provide an option to inline C helpers into Rust 2026-03-30 02:03:52 +02:00
.mailmap drm fixes for 7.1-rc2 2026-05-01 16:56:08 -07:00
.pylintrc docs: Move the python libraries to tools/lib/python 2025-11-18 09:22:40 -07:00
.rustfmt.toml
COPYING
CREDITS Delete some obsolete networking code 2026-04-24 09:41:58 -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 drm fixes for 7.1-rc2 2026-05-01 16:56:08 -07:00
Makefile Linux 7.1-rc2 2026-05-03 14:21:25 -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