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Frederic Weisbecker b672daa89d rcu: Fix racy re-initialization of irq_work causing hangs commit `61399e0c54` upstream. RCU re-initializes the deferred QS irq work everytime before attempting to queue it. However there are situations where the irq work is attempted to be queued even though it is already queued. In that case re-initializing messes-up with the irq work queue that is about to be handled. The chances for that to happen are higher when the architecture doesn't support self-IPIs and irq work are then all lazy, such as with the following sequence: 1) rcu_read_unlock() is called when IRQs are disabled and there is a grace period involving blocked tasks on the node. The irq work is then initialized and queued. 2) The related tasks are unblocked and the CPU quiescent state is reported. rdp->defer_qs_iw_pending is reset to DEFER_QS_IDLE, allowing the irq work to be requeued in the future (note the previous one hasn't fired yet). 3) A new grace period starts and the node has blocked tasks. 4) rcu_read_unlock() is called when IRQs are disabled again. The irq work is re-initialized (but it's queued! and its node is cleared) and requeued. Which means it's requeued to itself. 5) The irq work finally fires with the tick. But since it was requeued to itself, it loops and hangs. Fix this with initializing the irq work only once before the CPU boots. Fixes: `b41642c877` ("rcu: Fix rcu_read_unlock() deadloop due to IRQ work") Reported-by: kernel test robot <oliver.sang@intel.com> Closes: https://lore.kernel.org/oe-lkp/202508071303.c1134cce-lkp@intel.com Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com> Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.upadhyay@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		History 2025-08-20 18:30:58 +02:00
arch	arm64: dts: ti: k3-j722s-evm: Fix USB gpio-hog level for Type-C	2025-08-20 18:30:57 +02:00
block	block: Introduce bio_needs_zone_write_plugging()	2025-08-20 18:30:51 +02:00
certs	sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3	2024-09-20 19:52:48 +03:00
crypto	crypto: jitter - fix intermediary handling	2025-08-20 18:30:42 +02:00
Documentation	Documentation: ACPI: Fix parent device references	2025-08-20 18:30:15 +02:00
drivers	drm/amd/display: Allow DCN301 to clear update flags	2025-08-20 18:30:58 +02:00
fs	smb: client: fix netns refcount leak after net_passive changes	2025-08-20 18:30:57 +02:00
include	ata: libata-sata: Add link_power_management_supported sysfs attribute	2025-08-20 18:30:57 +02:00
init	io_uring: fix breakage in EXPERT menu	2025-08-15 12:13:32 +02:00
io_uring	io_uring/rw: cast rw->flags assignment to rwf_t	2025-08-20 18:30:58 +02:00
ipc	ipc: fix to protect IPCS lookups using RCU	2025-06-27 11:11:22 +01:00
kernel
lib	lib/sbitmap: convert shallow_depth from one word to the whole sbitmap	2025-08-20 18:30:49 +02:00
LICENSES	LICENSES: add 0BSD license text	2024-09-01 20:43:24 -07:00
mm	mm/kmemleak: avoid deadlock by moving pr_warn() outside kmemleak_lock	2025-08-20 18:30:55 +02:00
net	net: better track kernel sockets lifetime	2025-08-20 18:30:56 +02:00
rust	rust: workaround `rustdoc` target modifiers bug	2025-08-20 18:30:57 +02:00
samples	samples: mei: Fix building on musl libc	2025-08-15 12:13:38 +02:00
scripts	kconfig: lxdialog: fix 'space' to (de)select options	2025-08-20 18:30:48 +02:00
security	apparmor: fix x_table_lookup when stacking is not the first entry	2025-08-20 18:30:47 +02:00
sound	ASoC: fsl_sai: replace regmap_write with regmap_update_bits	2025-08-20 18:30:50 +02:00
tools	tools/hv: fcopy: Fix irregularities with size of ring buffer	2025-08-20 18:30:56 +02:00
usr	kbuild: hdrcheck: fix cross build with clang	2025-03-13 13:02:18 +01:00
virt	KVM: Allow CPU to reschedule while setting per-page memory attributes	2025-07-17 18:37:08 +02:00
.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: give Clippy the minimum supported Rust version	2025-08-01 09:48:44 +01:00
.cocciconfig	scripts: add Linux .cocciconfig for coccinelle	2016-07-22 12:13:39 +02:00
.editorconfig	.editorconfig: remove trim_trailing_whitespace option	2024-06-13 16:47:52 +02:00
.get_maintainer.ignore	Add Jeff Kirsher to .get_maintainer.ignore	2024-03-08 11:36:54 +00:00
.gitattributes	.gitattributes: set diff driver for Rust source code files	2023-05-31 17:48:25 +02:00
.gitignore	rust: introduce `.clippy.toml`	2025-03-13 13:01:42 +01:00
.mailmap	mailmap: add entry for Thorsten Blum	2024-11-07 14:14:59 -08:00
.rustfmt.toml	rust: add `.rustfmt.toml`	2022-09-28 09:02:20 +02:00
COPYING	COPYING: state that all contributions really are covered by this file	2020-02-10 13:32:20 -08:00
CREDITS	MAINTAINERS: Remove self from DSA entry	2024-11-03 12:52:38 -08:00
Kbuild	Kbuild updates for v6.1	2022-10-10 12:00:45 -07:00
Kconfig	kbuild: ensure full rebuild when the compiler is updated	2020-05-12 13:28:33 +09:00
MAINTAINERS	MAINTAINERS: Update Alexey Makhalov's email address	2025-05-22 14:29:46 +02:00
Makefile	Linux 6.12.42	2025-08-15 12:14:14 +02:00
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.