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Maciej Andrzejewski ICEYE 40de151be9 serial: uartlite: fix PM runtime usage count underflow on probe 
commit d54801cd50 upstream.

ulite_probe() calls pm_runtime_put_autosuspend() at the end of probe
without holding a corresponding PM runtime reference for non-console
ports.

During ulite_assign(), uart_add_one_port() triggers uart_configure_port()
which calls ulite_pm() via uart_change_pm(). For non-console ports, the
UART core performs a balanced get/put cycle:

  uart_change_pm(ON)  -> ulite_pm() -> pm_runtime_get_sync()        +1
  uart_change_pm(OFF) -> ulite_pm() -> pm_runtime_put_autosuspend() -1

This leaves no spare reference for the pm_runtime_put_autosuspend() at
the end of probe. The PM runtime core prevents the count from actually
going below zero, and instead triggers a
"Runtime PM usage count underflow!" warning.

For console ports the bug is masked: the UART core skips the
uart_change_pm(OFF) call, so the UART core's unbalanced get happens to
pair with probe's trailing put.

Add pm_runtime_get_noresume() before pm_runtime_enable() to take an
explicit probe-owned reference that the trailing
pm_runtime_put_autosuspend() can release. This ensures a correct usage
count regardless of whether the port is a console.

Fixes: 5bbe10a694 ("tty: serial: uartlite: Add runtime pm support")
Cc: stable <stable@kernel.org>
Signed-off-by: Maciej Andrzejewski ICEYE <maciej.andrzejewski@m-works.net>
Link: https://patch.msgid.link/20260305123746.4152800-1-maciej.andrzejewski@m-works.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2026-04-18 10:33:18 +02:00
arch x86/apic: Disable x2apic on resume if the kernel expects so 2026-04-18 10:33:16 +02:00
block blk-mq-debugfs: add missing debugfs_mutex in blk_mq_debugfs_register_hctxs() 2026-03-04 07:19:59 -05:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:22:01 +02:00
crypto crypto: authencesn - reject too-short AAD (assoclen<8) to match ESP/ESN spec 2026-02-06 16:41:53 +01:00
Documentation net: dpaa2: replace dpaa2_mac_is_type_fixed() with dpaa2_mac_is_type_phy() 2026-04-18 10:33:09 +02:00
drivers serial: uartlite: fix PM runtime usage count underflow on probe 2026-04-18 10:33:18 +02:00
fs btrfs: abort transaction on failure to update root in the received subvol ioctl 2026-04-18 10:33:16 +02:00
include irqchip/gic-v3-its: Limit number of per-device MSIs to the range the ITS supports 2026-04-18 10:33:15 +02:00
init init: handle bootloader identifier in kernel parameters 2025-10-19 16:21:45 +02:00
io_uring io_uring/io-wq: check IO_WQ_BIT_EXIT inside work run loop 2026-04-18 10:33:17 +02:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:05:26 +01:00
kernel bpf: Forget ranges when refining tnum after JSET 2026-04-18 10:33:16 +02:00
lib lib/bootconfig: check bounds before writing in __xbc_open_brace() 2026-04-18 10:33:16 +02:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm mm, page_alloc, thp: prevent reclaim for __GFP_THISNODE THP allocations 2026-03-04 07:20:30 -05:00
net Bluetooth: L2CAP: Validate L2CAP_INFO_RSP payload length before access 2026-04-18 10:33:17 +02:00
samples samples: mei: Fix building on musl libc 2025-08-28 16:24:07 +02:00
scripts modpost: Amend ppc64 save/restfpr symnames for -Os build 2026-03-04 07:20:06 -05:00
security apparmor: fix invalid deref of rawdata when export_binary is unset 2026-03-04 07:19:53 -05:00
sound ASoC: detect empty DMI strings 2026-04-18 10:33:13 +02:00
tools selftests: mptcp: more stable simult_flows tests 2026-04-18 10:33:09 +02:00
usr kbuild: hdrcheck: fix cross build with clang 2025-06-27 11:05:22 +01:00
virt KVM: Don't clobber irqfd routing type when deassigning irqfd 2026-02-11 13:35:27 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore Remove *.orig pattern from .gitignore 2024-10-17 15:11:10 +02:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS staging: rtl8712: Remove driver using deprecated API wext 2025-12-07 06:09:36 +09:00
Makefile Linux 5.15.202 2026-03-04 07:37:37 -05:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -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 Restructured Text 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.