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Chen Ridong 3cb97a927f cgroup/cpuset: remove kernfs active break A warning was found: WARNING: CPU: 10 PID: 3486953 at fs/kernfs/file.c:828 CPU: 10 PID: 3486953 Comm: rmdir Kdump: loaded Tainted: G RIP: 0010:kernfs_should_drain_open_files+0x1a1/0x1b0 RSP: 0018:ffff8881107ef9e0 EFLAGS: 00010202 RAX: 0000000080000002 RBX: ffff888154738c00 RCX: dffffc0000000000 RDX: 0000000000000007 RSI: 0000000000000004 RDI: ffff888154738c04 RBP: ffff888154738c04 R08: ffffffffaf27fa15 R09: ffffed102a8e7180 R10: ffff888154738c07 R11: 0000000000000000 R12: ffff888154738c08 R13: ffff888750f8c000 R14: ffff888750f8c0e8 R15: ffff888154738ca0 FS: 00007f84cd0be740(0000) GS:ffff8887ddc00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000555f9fbe00c8 CR3: 0000000153eec001 CR4: 0000000000370ee0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: kernfs_drain+0x15e/0x2f0 __kernfs_remove+0x165/0x300 kernfs_remove_by_name_ns+0x7b/0xc0 cgroup_rm_file+0x154/0x1c0 cgroup_addrm_files+0x1c2/0x1f0 css_clear_dir+0x77/0x110 kill_css+0x4c/0x1b0 cgroup_destroy_locked+0x194/0x380 cgroup_rmdir+0x2a/0x140 It can be explained by: rmdir echo 1 > cpuset.cpus kernfs_fop_write_iter // active=0 cgroup_rm_file kernfs_remove_by_name_ns kernfs_get_active // active=1 __kernfs_remove // active=0x80000002 kernfs_drain cpuset_write_resmask wait_event //waiting (active == 0x80000001) kernfs_break_active_protection // active = 0x80000001 // continue kernfs_unbreak_active_protection // active = 0x80000002 ... kernfs_should_drain_open_files // warning occurs kernfs_put_active This warning is caused by 'kernfs_break_active_protection' when it is writing to cpuset.cpus, and the cgroup is removed concurrently. The commit `3a5a6d0c2b` ("cpuset: don't nest cgroup_mutex inside get_online_cpus()") made cpuset_hotplug_workfn asynchronous, This change involves calling flush_work(), which can create a multiple processes circular locking dependency that involve cgroup_mutex, potentially leading to a deadlock. To avoid deadlock. the commit `76bb5ab8f6` ("cpuset: break kernfs active protection in cpuset_write_resmask()") added 'kernfs_break_active_protection' in the cpuset_write_resmask. This could lead to this warning. After the commit `2125c0034c` ("cgroup/cpuset: Make cpuset hotplug processing synchronous"), the cpuset_write_resmask no longer needs to wait the hotplug to finish, which means that concurrent hotplug and cpuset operations are no longer possible. Therefore, the deadlock doesn't exist anymore and it does not have to 'break active protection' now. To fix this warning, just remove kernfs_break_active_protection operation in the 'cpuset_write_resmask'. Fixes: `bdb2fd7fc5` ("kernfs: Skip kernfs_drain_open_files() more aggressively") Fixes: `76bb5ab8f6` ("cpuset: break kernfs active protection in cpuset_write_resmask()") Reported-by: Ji Fa <jifa@huawei.com> Signed-off-by: Chen Ridong <chenridong@huawei.com> Acked-by: Waiman Long <longman@redhat.com> Signed-off-by: Tejun Heo <tj@kernel.org>		2025-01-08 15:54:39 -10:00
arch	- Make sure the PEBS buffer is drained before reconfiguring the hardware	2024-12-09 10:31:35 -08:00
block	blk-mq: move cpuhp callback registering out of q->sysfs_lock	2024-12-06 09:48:46 -07:00
certs	sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3	2024-09-20 19:52:48 +03:00
crypto	module: Convert symbol namespace to string literal	2024-12-02 11:34:44 -08:00
Documentation	- Remove wrong enqueueing of a task for a later wakeup when a task blocks on	2024-12-09 10:28:55 -08:00
drivers	Two reverts and two EN7581 driver fixes:	2024-12-10 18:21:40 -08:00
fs	for-6.13-rc2-tag	2024-12-10 18:18:01 -08:00
include	- Remove if_not_guard() as it is generating incorrect code	2024-12-09 10:34:41 -08:00
init	- The series "resource: A couple of cleanups" from Andy Shevchenko	2024-11-25 16:09:48 -08:00
io_uring	io_uring: Change res2 parameter type in io_uring_cmd_done	2024-12-03 06:33:13 -07:00
ipc	- The series "resource: A couple of cleanups" from Andy Shevchenko	2024-11-25 16:09:48 -08:00
kernel	cgroup/cpuset: remove kernfs active break	2025-01-08 15:54:39 -10:00
lib	- Remove if_not_guard() as it is generating incorrect code	2024-12-09 10:34:41 -08:00
LICENSES	LICENSES: add 0BSD license text	2024-09-01 20:43:24 -07:00
mm	24 hotfixes. 17 are cc:stable. 15 are MM and 9 are non-MM.	2024-12-08 11:26:13 -08:00
net	BPF fixes:	2024-12-06 15:07:48 -08:00
rust	block-6.13-20242901	2024-11-30 15:47:29 -08:00
samples	BPF fixes:	2024-12-06 15:07:48 -08:00
scripts	Kbuild fixes for v6.13	2024-12-08 12:01:06 -08:00
security	Including fixes from can and netfilter.	2024-12-05 10:25:06 -08:00
sound	sound fixes for 6.13-rc2	2024-12-06 11:46:39 -08:00
tools	cgroup/cpuset: Prevent leakage of isolated CPUs into sched domains	2024-12-11 05:45:52 -10:00
usr	initramfs: shorten cmd_initfs in usr/Makefile	2024-07-16 01:07:52 +09:00
virt	VFIO updates for v6.13	2024-11-27 12:57:03 -08:00
.clang-format	clang-format: Update with v6.11-rc1's `for_each` macro list	2024-08-02 13:20:31 +02:00
.clippy.toml	rust: enable Clippy's `check-private-items`	2024-10-07 21:39:57 +02:00
.cocciconfig
.editorconfig	.editorconfig: remove trim_trailing_whitespace option	2024-06-13 16:47:52 +02:00
.get_maintainer.ignore	MAINTAINERS: Retire Ralf Baechle	2024-11-12 15:48:59 +01:00
.gitattributes	.gitattributes: set diff driver for Rust source code files	2023-05-31 17:48:25 +02:00
.gitignore	Kbuild updates for v6.13	2024-11-30 13:41:50 -08:00
.mailmap	media updates for v6.13-rc1	2024-11-20 14:01:15 -08:00
.rustfmt.toml	rust: add `.rustfmt.toml`	2022-09-28 09:02:20 +02:00
COPYING
CREDITS	cgroup: Changes for v6.13	2024-11-20 09:54:49 -08:00
Kbuild	Kbuild updates for v6.1	2022-10-10 12:00:45 -07:00
Kconfig
MAINTAINERS	arm64 fixes for 6.13-rc2:	2024-12-06 13:47:55 -08:00
Makefile	Linux 6.13-rc2	2024-12-08 14:03:39 -08:00
README	README: Fix spelling	2024-03-18 03:36:32 -06:00

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.