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Sebastian Andrzej Siewior 63ee96c7f4 ALSA: pcm: Disable bottom softirqs as part of spin_lock_irq() on PREEMPT_RT 
[ Upstream commit 9fc4a3da9a ]

snd_pcm_group_lock_irq() acquires a spinlock_t and disables interrupts
via spin_lock_irq(). This also implicitly disables the handling of
softirqs such as TIMER_SOFTIRQ.
On PREEMPT_RT softirqs are preemptible and spin_lock_irq() does not
disable them. That means a timer can be invoked during spin_lock_irq()
on the same CPU. Due to synchronisations reasons local_bh_disable() has
a per-CPU lock named softirq_ctrl.lock which synchronizes individual
softirq against each other.
syz-bot managed to trigger a lockdep report where softirq_ctrl.lock is
acquired in hrtimer_cancel() in addition to hrtimer_run_softirq(). This
is a possible deadlock.

The softirq_ctrl.lock can not be made part of spin_lock_irq() as this
would lead to too much synchronisation against individual threads on the
system. To avoid the possible deadlock, softirqs must be manually
disabled before the lock is acquired.

Disable softirqs before the lock is acquired on PREEMPT_RT.

Reported-by: syzbot+10b4363fb0f46527f3f3@syzkaller.appspotmail.com
Fixes: d2d6422f8b ("x86: Allow to enable PREEMPT_RT.")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2025-10-15 12:00:12 +02:00
arch bpf, arm64: Call bpf_jit_binary_pack_finalize() in bpf_jit_free() 2025-10-15 12:00:02 +02:00
block block: use int to store blk_stack_limits() return value 2025-10-15 11:59:58 +02:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: rng - Ensure set_ent is always present 2025-10-12 12:57:19 +02:00
Documentation platform/x86: lg-laptop: Fix WMAB call in fan_mode_store() 2025-10-02 13:44:12 +02:00
drivers wifi: mt76: mt7915: fix mt7981 pre-calibration 2025-10-15 12:00:11 +02:00
fs f2fs: fix to mitigate overhead of f2fs_zero_post_eof_page() 2025-10-15 12:00:12 +02:00
include bpf: Enforce expected_attach_type for tailcall compatibility 2025-10-15 12:00:04 +02:00
init init: INITRAMFS_PRESERVE_MTIME should depend on BLK_DEV_INITRD 2025-10-15 11:59:53 +02:00
io_uring io_uring: fix incorrect io_kiocb reference in io_link_skb 2025-09-25 11:13:49 +02:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:11:22 +01:00
kernel bpf: Enforce expected_attach_type for tailcall compatibility 2025-10-15 12:00:04 +02:00
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: swap: check for stable address space before operating on the VMA 2025-10-06 11:17:52 +02:00
net ipvs: Use READ_ONCE/WRITE_ONCE for ipvs->enable 2025-10-15 12:00:10 +02:00
rust rust: block: fix srctree/ links 2025-10-12 12:57:16 +02:00
samples ftrace/samples: Fix function size computation 2025-09-19 16:35:44 +02:00
scripts gcc-plugins: Remove TODO_verify_il for GCC >= 16 2025-10-06 11:17:52 +02:00
security lsm: CONFIG_LSM can depend on CONFIG_SECURITY 2025-10-15 11:59:55 +02:00
sound ALSA: pcm: Disable bottom softirqs as part of spin_lock_irq() on PREEMPT_RT 2025-10-15 12:00:12 +02:00
tools libbpf: Fix error when st-prefix_ops and ops from differ btf 2025-10-15 12:00:04 +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 6.12.52 2025-10-12 12:57:19 +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.