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When I run the NVME over TCP test in virtme-ng, I get the following
"suspicious RCU usage" warning in nvme_mpath_add_sysfs_link():
'''
[ 5.024557][ T44] nvmet: Created nvm controller 1 for subsystem nqn.2025-06.org.nvmexpress.mptcp for NQN nqn.2014-08.org.nvmexpress:uuid:f7f6b5e0-ff97-4894-98ac-c85309e0bc77.
[ 5.027401][ T183] nvme nvme0: creating 2 I/O queues.
[ 5.029017][ T183] nvme nvme0: mapped 2/0/0 default/read/poll queues.
[ 5.032587][ T183] nvme nvme0: new ctrl: NQN "nqn.2025-06.org.nvmexpress.mptcp", addr 127.0.0.1:4420, hostnqn: nqn.2014-08.org.nvmexpress:uuid:f7f6b5e0-ff97-4894-98ac-c85309e0bc77
[ 5.042214][ T25]
[ 5.042440][ T25] =============================
[ 5.042579][ T25] WARNING: suspicious RCU usage
[ 5.042705][ T25] 6.16.0-rc3+ #23 Not tainted
[ 5.042812][ T25] -----------------------------
[ 5.042934][ T25] drivers/nvme/host/multipath.c:1203 RCU-list traversed in non-reader section!!
[ 5.043111][ T25]
[ 5.043111][ T25] other info that might help us debug this:
[ 5.043111][ T25]
[ 5.043341][ T25]
[ 5.043341][ T25] rcu_scheduler_active = 2, debug_locks = 1
[ 5.043502][ T25] 3 locks held by kworker/u9:0/25:
[ 5.043615][ T25] #0: ffff888008730948 ((wq_completion)async){+.+.}-{0:0}, at: process_one_work+0x7ed/0x1350
[ 5.043830][ T25] #1: ffffc900001afd40 ((work_completion)(&entry->work)){+.+.}-{0:0}, at: process_one_work+0xcf3/0x1350
[ 5.044084][ T25] #2: ffff888013ee0020 (&head->srcu){.+.+}-{0:0}, at: nvme_mpath_add_sysfs_link.part.0+0xb4/0x3a0
[ 5.044300][ T25]
[ 5.044300][ T25] stack backtrace:
[ 5.044439][ T25] CPU: 0 UID: 0 PID: 25 Comm: kworker/u9:0 Not tainted 6.16.0-rc3+ #23 PREEMPT(full)
[ 5.044441][ T25] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[ 5.044442][ T25] Workqueue: async async_run_entry_fn
[ 5.044445][ T25] Call Trace:
[ 5.044446][ T25] <TASK>
[ 5.044449][ T25] dump_stack_lvl+0x6f/0xb0
[ 5.044453][ T25] lockdep_rcu_suspicious.cold+0x4f/0xb1
[ 5.044457][ T25] nvme_mpath_add_sysfs_link.part.0+0x2fb/0x3a0
[ 5.044459][ T25] ? queue_work_on+0x90/0xf0
[ 5.044461][ T25] ? lockdep_hardirqs_on+0x78/0x110
[ 5.044466][ T25] nvme_mpath_set_live+0x1e9/0x4f0
[ 5.044470][ T25] nvme_mpath_add_disk+0x240/0x2f0
[ 5.044472][ T25] ? __pfx_nvme_mpath_add_disk+0x10/0x10
[ 5.044475][ T25] ? add_disk_fwnode+0x361/0x580
[ 5.044480][ T25] nvme_alloc_ns+0x81c/0x17c0
[ 5.044483][ T25] ? kasan_quarantine_put+0x104/0x240
[ 5.044487][ T25] ? __pfx_nvme_alloc_ns+0x10/0x10
[ 5.044495][ T25] ? __pfx_nvme_find_get_ns+0x10/0x10
[ 5.044496][ T25] ? rcu_read_lock_any_held+0x45/0xa0
[ 5.044498][ T25] ? validate_chain+0x232/0x4f0
[ 5.044503][ T25] nvme_scan_ns+0x4c8/0x810
[ 5.044506][ T25] ? __pfx_nvme_scan_ns+0x10/0x10
[ 5.044508][ T25] ? find_held_lock+0x2b/0x80
[ 5.044512][ T25] ? ktime_get+0x16d/0x220
[ 5.044517][ T25] ? kvm_clock_get_cycles+0x18/0x30
[ 5.044520][ T25] ? __pfx_nvme_scan_ns_async+0x10/0x10
[ 5.044522][ T25] async_run_entry_fn+0x97/0x560
[ 5.044523][ T25] ? rcu_is_watching+0x12/0xc0
[ 5.044526][ T25] process_one_work+0xd3c/0x1350
[ 5.044532][ T25] ? __pfx_process_one_work+0x10/0x10
[ 5.044536][ T25] ? assign_work+0x16c/0x240
[ 5.044539][ T25] worker_thread+0x4da/0xd50
[ 5.044545][ T25] ? __pfx_worker_thread+0x10/0x10
[ 5.044546][ T25] kthread+0x356/0x5c0
[ 5.044548][ T25] ? __pfx_kthread+0x10/0x10
[ 5.044549][ T25] ? ret_from_fork+0x1b/0x2e0
[ 5.044552][ T25] ? __lock_release.isra.0+0x5d/0x180
[ 5.044553][ T25] ? ret_from_fork+0x1b/0x2e0
[ 5.044555][ T25] ? rcu_is_watching+0x12/0xc0
[ 5.044557][ T25] ? __pfx_kthread+0x10/0x10
[ 5.044559][ T25] ret_from_fork+0x218/0x2e0
[ 5.044561][ T25] ? __pfx_kthread+0x10/0x10
[ 5.044562][ T25] ret_from_fork_asm+0x1a/0x30
[ 5.044570][ T25] </TASK>
'''
This patch uses sleepable RCU version of helper list_for_each_entry_srcu()
instead of list_for_each_entry_rcu() to fix it.
Fixes:
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.