Sungwoo Kim fc71f409b2 nvme-pci: Fix race bug in nvme_poll_irqdisable()
In the following scenario, pdev can be disabled between (1) and (3) by
(2). This sets pdev->msix_enabled = 0. Then, pci_irq_vector() will
return MSI-X IRQ(>15) for (1) whereas return INTx IRQ(<=15) for (2).
This causes IRQ warning because it tries to enable INTx IRQ that has
never been disabled before.

To fix this, save IRQ number into a local variable and ensure
disable_irq() and enable_irq() operate on the same IRQ number.  Even if
pci_free_irq_vectors() frees the IRQ concurrently, disable_irq() and
enable_irq() on a stale IRQ number is still valid and safe, and the
depth accounting reamins balanced.

task 1:
nvme_poll_irqdisable()
  disable_irq(pci_irq_vector(pdev, nvmeq->cq_vector)) ...(1)
  enable_irq(pci_irq_vector(pdev, nvmeq->cq_vector))  ...(3)

task 2:
nvme_reset_work()
  nvme_dev_disable()
    pdev->msix_enable = 0;  ...(2)

crash log:

------------[ cut here ]------------
Unbalanced enable for IRQ 10
WARNING: kernel/irq/manage.c:753 at __enable_irq+0x102/0x190 kernel/irq/manage.c:753, CPU#1: kworker/1:0H/26
Modules linked in:
CPU: 1 UID: 0 PID: 26 Comm: kworker/1:0H Not tainted 6.19.0-dirty #9 PREEMPT(voluntary)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
Workqueue: kblockd blk_mq_timeout_work
RIP: 0010:__enable_irq+0x107/0x190 kernel/irq/manage.c:753
Code: ff df 48 89 fa 48 c1 ea 03 0f b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 04 84 d2 75 79 48 8d 3d 2e 7a 3f 05 41 8b 74 24 2c <67> 48 0f b9 3a e8 ef b9 21 00 5b 41 5c 5d e9 46 54 66 03 e8 e1 b9
RSP: 0018:ffffc900001bf550 EFLAGS: 00010046
RAX: 0000000000000007 RBX: 0000000000000000 RCX: ffffffffb20c0e90
RDX: 0000000000000000 RSI: 000000000000000a RDI: ffffffffb74b88f0
RBP: ffffc900001bf560 R08: ffff88800197cf00 R09: 0000000000000001
R10: 0000000000000003 R11: 0000000000000003 R12: ffff8880012a6000
R13: 1ffff92000037eae R14: 000000000000000a R15: 0000000000000293
FS:  0000000000000000(0000) GS:ffff8880b49f7000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000555da4a25fa8 CR3: 00000000208e8000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 enable_irq+0x121/0x1e0 kernel/irq/manage.c:797
 nvme_poll_irqdisable+0x162/0x1c0 drivers/nvme/host/pci.c:1494
 nvme_timeout+0x965/0x14b0 drivers/nvme/host/pci.c:1744
 blk_mq_rq_timed_out block/blk-mq.c:1653 [inline]
 blk_mq_handle_expired+0x227/0x2d0 block/blk-mq.c:1721
 bt_iter+0x2fc/0x3a0 block/blk-mq-tag.c:292
 __sbitmap_for_each_set include/linux/sbitmap.h:269 [inline]
 sbitmap_for_each_set include/linux/sbitmap.h:290 [inline]
 bt_for_each block/blk-mq-tag.c:324 [inline]
 blk_mq_queue_tag_busy_iter+0x969/0x1e80 block/blk-mq-tag.c:536
 blk_mq_timeout_work+0x627/0x870 block/blk-mq.c:1763
 process_one_work+0x956/0x1aa0 kernel/workqueue.c:3257
 process_scheduled_works kernel/workqueue.c:3340 [inline]
 worker_thread+0x65c/0xe60 kernel/workqueue.c:3421
 kthread+0x41a/0x930 kernel/kthread.c:463
 ret_from_fork+0x6f8/0x8c0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>
irq event stamp: 74478
hardirqs last  enabled at (74477): [<ffffffffb5720a9c>] __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:159 [inline]
hardirqs last  enabled at (74477): [<ffffffffb5720a9c>] _raw_spin_unlock_irq+0x2c/0x60 kernel/locking/spinlock.c:202
hardirqs last disabled at (74478): [<ffffffffb57207b5>] __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:108 [inline]
hardirqs last disabled at (74478): [<ffffffffb57207b5>] _raw_spin_lock_irqsave+0x85/0xa0 kernel/locking/spinlock.c:162
softirqs last  enabled at (74304): [<ffffffffb1e9466c>] __do_softirq kernel/softirq.c:656 [inline]
softirqs last  enabled at (74304): [<ffffffffb1e9466c>] invoke_softirq kernel/softirq.c:496 [inline]
softirqs last  enabled at (74304): [<ffffffffb1e9466c>] __irq_exit_rcu+0xdc/0x120 kernel/softirq.c:723
softirqs last disabled at (74287): [<ffffffffb1e9466c>] __do_softirq kernel/softirq.c:656 [inline]
softirqs last disabled at (74287): [<ffffffffb1e9466c>] invoke_softirq kernel/softirq.c:496 [inline]
softirqs last disabled at (74287): [<ffffffffb1e9466c>] __irq_exit_rcu+0xdc/0x120 kernel/softirq.c:723
---[ end trace 0000000000000000 ]---

Fixes: fa059b856a (nvme-pci: Simplify nvme_poll_irqdisable)
Acked-by: Chao Shi <cshi008@fiu.edu>
Acked-by: Weidong Zhu <weizhu@fiu.edu>
Acked-by: Dave Tian <daveti@purdue.edu>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sungwoo Kim <iam@sung-woo.kim>
Signed-off-by: Keith Busch <kbusch@kernel.org>
2026-03-10 08:20:29 -07:00
2026-01-26 19:07:09 -08:00
…
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
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* 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

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============

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

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

Welcome! Start your kernel development journey here:

* Getting Started: Documentation/process/development-process.rst
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* Coding Style: Documentation/process/coding-style.rst
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* 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
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---------------

Security documentation and hardening guides:

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

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* Driver API Guide: Documentation/driver-api/index.rst
* Driver Model: Documentation/driver-api/driver-model/driver.rst
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* 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.


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=========================

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