Shay Drory 2700b7e603 net/mlx5: DR, Fix circular locking dependency in dump
Fix a circular locking dependency between dbg_mutex and the domain
rx/tx mutexes that could lead to a deadlock.

The dump path in dr_dump_domain_all() was acquiring locks in the order:
  dbg_mutex -> rx.mutex -> tx.mutex

While the table/matcher creation paths acquire locks in the order:
  rx.mutex -> tx.mutex -> dbg_mutex

This inverted lock ordering creates a circular dependency. Fix this by
changing dr_dump_domain_all() to acquire the domain lock before
dbg_mutex, matching the order used in mlx5dr_table_create() and
mlx5dr_matcher_create().

Lockdep splat:
 ======================================================
 WARNING: possible circular locking dependency detected
 6.19.0-rc6net_next_e817c4e #1 Not tainted
 ------------------------------------------------------
 sos/30721 is trying to acquire lock:
 ffff888102df5900 (&dmn->info.rx.mutex){+.+.}-{4:4}, at:
dr_dump_start+0x131/0x450 [mlx5_core]

 but task is already holding lock:
 ffff888102df5bc0 (&dmn->dump_info.dbg_mutex){+.+.}-{4:4}, at:
dr_dump_start+0x10b/0x450 [mlx5_core]

 which lock already depends on the new lock.

 the existing dependency chain (in reverse order) is:

 -> #2 (&dmn->dump_info.dbg_mutex){+.+.}-{4:4}:
        __mutex_lock+0x91/0x1060
        mlx5dr_matcher_create+0x377/0x5e0 [mlx5_core]
        mlx5_cmd_dr_create_flow_group+0x62/0xd0 [mlx5_core]
        mlx5_create_flow_group+0x113/0x1c0 [mlx5_core]
        mlx5_chains_create_prio+0x453/0x2290 [mlx5_core]
        mlx5_chains_get_table+0x2e2/0x980 [mlx5_core]
        esw_chains_create+0x1e6/0x3b0 [mlx5_core]
        esw_create_offloads_fdb_tables.cold+0x62/0x63f [mlx5_core]
        esw_offloads_enable+0x76f/0xd20 [mlx5_core]
        mlx5_eswitch_enable_locked+0x35a/0x500 [mlx5_core]
        mlx5_devlink_eswitch_mode_set+0x561/0x950 [mlx5_core]
        devlink_nl_eswitch_set_doit+0x67/0xe0
        genl_family_rcv_msg_doit+0xe0/0x130
        genl_rcv_msg+0x188/0x290
        netlink_rcv_skb+0x4b/0xf0
        genl_rcv+0x24/0x40
        netlink_unicast+0x1ed/0x2c0
        netlink_sendmsg+0x210/0x450
        __sock_sendmsg+0x38/0x60
        __sys_sendto+0x119/0x180
        __x64_sys_sendto+0x20/0x30
        do_syscall_64+0x70/0xd00
        entry_SYSCALL_64_after_hwframe+0x4b/0x53

 -> #1 (&dmn->info.tx.mutex){+.+.}-{4:4}:
        __mutex_lock+0x91/0x1060
        mlx5dr_table_create+0x11d/0x530 [mlx5_core]
        mlx5_cmd_dr_create_flow_table+0x62/0x140 [mlx5_core]
        __mlx5_create_flow_table+0x46f/0x960 [mlx5_core]
        mlx5_create_flow_table+0x16/0x20 [mlx5_core]
        esw_create_offloads_fdb_tables+0x136/0x240 [mlx5_core]
        esw_offloads_enable+0x76f/0xd20 [mlx5_core]
        mlx5_eswitch_enable_locked+0x35a/0x500 [mlx5_core]
        mlx5_devlink_eswitch_mode_set+0x561/0x950 [mlx5_core]
        devlink_nl_eswitch_set_doit+0x67/0xe0
        genl_family_rcv_msg_doit+0xe0/0x130
        genl_rcv_msg+0x188/0x290
        netlink_rcv_skb+0x4b/0xf0
        genl_rcv+0x24/0x40
        netlink_unicast+0x1ed/0x2c0
        netlink_sendmsg+0x210/0x450
        __sock_sendmsg+0x38/0x60
        __sys_sendto+0x119/0x180
        __x64_sys_sendto+0x20/0x30
        do_syscall_64+0x70/0xd00
        entry_SYSCALL_64_after_hwframe+0x4b/0x53

 -> #0 (&dmn->info.rx.mutex){+.+.}-{4:4}:
        __lock_acquire+0x18b6/0x2eb0
        lock_acquire+0xd3/0x2c0
        __mutex_lock+0x91/0x1060
        dr_dump_start+0x131/0x450 [mlx5_core]
        seq_read_iter+0xe3/0x410
        seq_read+0xfb/0x130
        full_proxy_read+0x53/0x80
        vfs_read+0xba/0x330
        ksys_read+0x65/0xe0
        do_syscall_64+0x70/0xd00
        entry_SYSCALL_64_after_hwframe+0x4b/0x53

  Possible unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   lock(&dmn->dump_info.dbg_mutex);
                                lock(&dmn->info.tx.mutex);
                                lock(&dmn->dump_info.dbg_mutex);
   lock(&dmn->info.rx.mutex);

                   *** DEADLOCK ***

Fixes: 9222f0b27d ("net/mlx5: DR, Add support for dumping steering info")
Signed-off-by: Shay Drory <shayd@nvidia.com>
Reviewed-by: Yevgeny Kliteynik <kliteyn@nvidia.com>
Reviewed-by: Alex Vesker <valex@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20260224114652.1787431-2-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2026-02-25 20:01:43 -08:00
2026-01-26 19:07:09 -08:00
2022-09-28 09:02:20 +02:00
2025-02-19 14:53:27 -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
Description
No description provided
Readme 3.5 GiB
Languages
C 97.1%
Assembly 1%
Shell 0.6%
Rust 0.4%
Python 0.4%
Other 0.3%