Linux kernel ============ The Linux kernel is the core of any Linux operating system. It manages hardware, system resources, and provides the fundamental services for all other software. Quick Start ----------- * Report a bug: See Documentation/admin-guide/reporting-issues.rst * Get the latest kernel: https://kernel.org * Build the kernel: See Documentation/admin-guide/quickly-build-trimmed-linux.rst * Join the community: https://lore.kernel.org/ Essential Documentation ----------------------- All users should be familiar with: * Building requirements: Documentation/process/changes.rst * Code of Conduct: Documentation/process/code-of-conduct.rst * License: See COPYING Documentation can be built with make htmldocs or viewed online at: https://www.kernel.org/doc/html/latest/ Who Are You? ============ Find your role below: * New Kernel Developer - Getting started with kernel development * Academic Researcher - Studying kernel internals and architecture * Security Expert - Hardening and vulnerability analysis * Backport/Maintenance Engineer - Maintaining stable kernels * System Administrator - Configuring and troubleshooting * Maintainer - Leading subsystems and reviewing patches * Hardware Vendor - Writing drivers for new hardware * Distribution Maintainer - Packaging kernels for distros * AI Coding Assistant - LLMs and AI-powered development tools For Specific Users ================== New Kernel Developer -------------------- Welcome! Start your kernel development journey here: * Getting Started: Documentation/process/development-process.rst * Your First Patch: Documentation/process/submitting-patches.rst * Coding Style: Documentation/process/coding-style.rst * Build System: Documentation/kbuild/index.rst * Development Tools: Documentation/dev-tools/index.rst * Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst * Core APIs: Documentation/core-api/index.rst Academic Researcher ------------------- Explore the kernel's architecture and internals: * Researcher Guidelines: Documentation/process/researcher-guidelines.rst * Memory Management: Documentation/mm/index.rst * Scheduler: Documentation/scheduler/index.rst * Networking Stack: Documentation/networking/index.rst * Filesystems: Documentation/filesystems/index.rst * RCU (Read-Copy Update): Documentation/RCU/index.rst * Locking Primitives: Documentation/locking/index.rst * Power Management: Documentation/power/index.rst Security Expert --------------- Security documentation and hardening guides: * Security Documentation: Documentation/security/index.rst * LSM Development: Documentation/security/lsm-development.rst * Self Protection: Documentation/security/self-protection.rst * Reporting Vulnerabilities: Documentation/process/security-bugs.rst * CVE Procedures: Documentation/process/cve.rst * Embargoed Hardware Issues: Documentation/process/embargoed-hardware-issues.rst * Security Features: Documentation/userspace-api/seccomp_filter.rst Backport/Maintenance Engineer ----------------------------- Maintain and stabilize kernel versions: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * Backporting Guide: Documentation/process/backporting.rst * Applying Patches: Documentation/process/applying-patches.rst * Subsystem Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git for Maintainers: Documentation/maintainer/configure-git.rst System Administrator -------------------- Configure, tune, and troubleshoot Linux systems: * Admin Guide: Documentation/admin-guide/index.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Sysctl Tuning: Documentation/admin-guide/sysctl/index.rst * Tracing/Debugging: Documentation/trace/index.rst * Performance Security: Documentation/admin-guide/perf-security.rst * Hardware Monitoring: Documentation/hwmon/index.rst Maintainer ---------- Lead kernel subsystems and manage contributions: * Maintainer Handbook: Documentation/maintainer/index.rst * Pull Requests: Documentation/maintainer/pull-requests.rst * Managing Patches: Documentation/maintainer/modifying-patches.rst * Rebasing and Merging: Documentation/maintainer/rebasing-and-merging.rst * Development Process: Documentation/process/maintainer-handbooks.rst * Maintainer Entry Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git Configuration: Documentation/maintainer/configure-git.rst Hardware Vendor --------------- Write drivers and support new hardware: * Driver API Guide: Documentation/driver-api/index.rst * Driver Model: Documentation/driver-api/driver-model/driver.rst * Device Drivers: Documentation/driver-api/infrastructure.rst * Bus Types: Documentation/driver-api/driver-model/bus.rst * Device Tree Bindings: Documentation/devicetree/bindings/ * Power Management: Documentation/driver-api/pm/index.rst * DMA API: Documentation/core-api/dma-api.rst Distribution Maintainer ----------------------- Package and distribute the kernel: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * ABI Documentation: Documentation/ABI/README * Kernel Configuration: Documentation/kbuild/kconfig.rst * Module Signing: Documentation/admin-guide/module-signing.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Tainted Kernels: Documentation/admin-guide/tainted-kernels.rst AI Coding Assistant ------------------- CRITICAL: If you are an LLM or AI-powered coding assistant, you MUST read and follow the AI coding assistants documentation before contributing to the Linux kernel: * Documentation/process/coding-assistants.rst This documentation contains essential requirements about licensing, attribution, and the Developer Certificate of Origin that all AI tools must comply with. Communication and Support ========================= * Mailing Lists: https://lore.kernel.org/ * IRC: #kernelnewbies on irc.oftc.net * Bugzilla: https://bugzilla.kernel.org/ * MAINTAINERS file: Lists subsystem maintainers and mailing lists * Email Clients: Documentation/process/email-clients.rst
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The proactive nr_dirty > gdtc->bg_thresh check in balance_dirty_pages()
only checks the global dirty threshold to start background writeback while
the writer is still free-running, but for strictlimit BDIs (eg fuse), the
per-wb dirty count can exceed the per-wb background threshold while the
global threshold is not yet exceeded, so background writeback for this
case never gets proactively started.
Add a per-wb threshold check for strictlimit BDIs so that background
writeback is started when wb_dirty exceeds wb_bg_thresh, which drains
dirty pages before the writer hits the throttle wall, matching the
proactive behavior that the global check provides for non-strictlimit
BDIs.
fio runs on fuse show about a 3-4% improvement in perf for buffered
writes:
fio --name=writeback_test --ioengine=psync --rw=write --bs=128k \
--size=2G --numjobs=4 --ramp_time=10 --runtime=20 \
--time_based --group_reporting=1 --direct=0
Link: https://lore.kernel.org/20260326234629.840938-2-joannelkoong@gmail.com
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Fix two error handling issues in kho_add_subtree(), where it doesn't
handle the error path correctly.
1. If fdt_setprop() fails after the subnode has been created, the
subnode is not removed. This leaves an incomplete node in the FDT
(missing "preserved-data" or "blob-size" properties).
2. The fdt_setprop() return value (an FDT error code) is stored
directly in err and returned to the caller, which expects -errno.
Fix both by storing fdt_setprop() results in fdt_err, jumping to a new
out_del_node label that removes the subnode on failure, and only setting
err = 0 on the success path, otherwise returning -ENOMEM (instead of
FDT_ERR_ errors that would come from fdt_setprop).
No user-visible changes. This patch fixes error handling in the KHO
(Kexec HandOver) subsystem, which is used to preserve data across kexec
reboots. The fix only affects a rare failure path during kexec
preparation — specifically when the kernel runs out of space in the
Flattened Device Tree buffer while registering preserved memory regions.
In the unlikely event that this error path was triggered, the old code
would leave a malformed node in the device tree and return an incorrect
error code to the calling subsystem, which could lead to confusing log
messages or incorrect recovery decisions. With this fix, the incomplete
node is properly cleaned up and the appropriate errno value is propagated,
this error code is not returned to the user.
Link: https://lore.kernel.org/20260410-kho_fix_send-v2-1-1b4debf7ee08@debian.org
Fixes: 3dc92c311498 ("kexec: add Kexec HandOver (KHO) generation helpers")
Signed-off-by: Breno Leitao <leitao@debian.org>
Suggested-by: Pratyush Yadav <pratyush@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Breno Leitao <leitao@debian.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
When session allocation fails during deserialization, the global 'err'
variable was not updated before returning. This caused subsequent calls
to luo_session_deserialize() to incorrectly report success.
Ensure 'err' is set to the error code from PTR_ERR(session). This ensures
that an error is correctly returned to userspace when it attempts to open
/dev/liveupdate in the new kernel if deserialization failed.
Link: https://lore.kernel.org/20260415193738.515491-1-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Cc: David Matlack <dmatlack@google.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Samiullah Khawaja <skhawaja@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Update my mailmap entry to point to my current email address.
Link: https://lore.kernel.org/ab2d502542c24491c191a76494717c340afb9a9b.1776691831.git.error27@gmail.com
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Commit 4c5d3365882d ("mm/vmalloc: allow to set node and align in
vrealloc") added the ability to force a new allocation if the current
pointer is on the wrong NUMA node, or if an alignment constraint is not
met, even if the user is shrinking the allocation.
On this path (need_realloc), the code allocates a new object of 'size'
bytes and then memcpy()s 'old_size' bytes into it. If the request is to
shrink the object (size < old_size), this results in an out-of-bounds
write on the new buffer.
Fix this by bounding the copy length by the new allocation size.
Link: https://lore.kernel.org/20260420114805.3572606-2-elver@google.com
Fixes: 4c5d3365882d ("mm/vmalloc: allow to set node and align in vrealloc")
Signed-off-by: Marco Elver <elver@google.com>
Reported-by: Harry Yoo (Oracle) <harry@kernel.org>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Reviewed-by: Harry Yoo (Oracle) <harry@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Pull clk fix from Stephen Boyd:
"One more fix for the merge window to avoid a boot hang on
Raspberry Pi 3B by marking the VEC clk critical so that it
doesn't get turned off and hang the bus"
* tag 'clk-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/clk/linux:
clk: bcm: rpi: Mark VEC clock as CLK_IGNORE_UNUSED
Pull PCIe TSP update from Dan Williams:
"A small update for the TSM core. It is arguably a fix and coming in
late as I have been offline the past few weeks:
- Drop class_create() for the 'tsm' class"
* tag 'tsm-for-7.1' of git://git.kernel.org/pub/scm/linux/kernel/git/devsec/tsm:
virt: coco: change tsm_class to a const struct
On Raspberry Pi 3B, the VEC clock is used by the VideoCore firmware
display driver, which remains active until the vc4 driver loads and
sends NOTIFY_DISPLAY_DONE. If this clock is disabled during boot, a bus
lockup happens and the firmware becomes unresponsive, causing a complete
system lockup.
Mark the VEC clock with CLK_IGNORE_UNUSED so it survives the unused
clock disablement and remains available until the vc4 driver takes over
display management.
Fixes: 672299736af6 ("clk: bcm: rpi: Manage clock rate in prepare/unprepare callbacks")
Reported-by: Mark Brown <broonie@kernel.org>
Closes: https://lore.kernel.org/r/5f0bec08-f458-4fba-8bf3-06817a100c4c@sirena.org.uk
Signed-off-by: Maíra Canal <mcanal@igalia.com>
Link: https://patch.msgid.link/20260401111416.562279-2-mcanal@igalia.com
Tested-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Brian Masney <bmasney@redhat.com> # Active contributor to clk
Reviewed-by: Stefan Wahren <wahrenst@gmx.net>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Pull Kbuild fixes from Nicolas Schier:
- builddeb - avoid recompiles for non-cross-compiles
Avoid triggering complete rebuilds for non-cross-compile Debian
package builds by only triggering the rebuild of host tools for
actual cross-compile builds
- Never respect CONFIG_WERROR / W=e to fixdep
Avoid spurious rebuilds of fixdep w/ and w/o -Werror during a single
kbuild invocation by never respecting CONFIG_WERROR for fixdep
* tag 'kbuild-fixes-7.1-1' of git://git.kernel.org/pub/scm/linux/kernel/git/kbuild/linux:
kbuild: Never respect CONFIG_WERROR / W=e to fixdep
kbuild: builddeb - avoid recompiles for non-cross-compiles
The class_create() call has been deprecated in favor of class_register()
as the driver core now allows for a struct class to be in read-only
memory. Change tsm_class to be a const struct class and drop the
class_create() call. Compile tested only.
Link: https://lore.kernel.org/all/2023040244-duffel-pushpin-f738@gregkh/
Changes with v1:
- Removed redundant int err variable.
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jori Koolstra <jkoolstra@xs4all.nl>
Reviewed-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Link: https://patch.msgid.link/20260306183325.245254-1-jkoolstra@xs4all.nl
Signed-off-by: Dan Williams <djbw@kernel.org>
* clk-samsung:
clk: samsung: exynos850: Add APM-to-AP mailbox clock
dt-bindings: clock: exynos850: Add APM_AP MAILBOX clock
clk: samsung: Use %pe format to simplify
clk: samsung: pll: Fix possible truncation in a9fraco recalc rate
clk: samsung: exynosautov920: add block G3D clock support
dt-bindings: clock: exynosautov920: add G3D clock definitions
clk: samsung: gs101: harmonise symbol names (clock arrays)
clk: samsung: artpec-9: Add initial clock support for ARTPEC-9 SoC
clk: samsung: Add clock PLL support for ARTPEC-9 SoC
dt-bindings: clock: Add ARTPEC-9 clock controller
* clk-qcom: (67 commits)
clk: qcom: gcc: Add multiple global clock controller driver for Nord SoC
clk: qcom: rpmh: Add support for Nord rpmh clocks
clk: qcom: Add TCSR clock driver for Nord SoC
dt-bindings: clock: qcom: Add Nord Global Clock Controller
dt-bindings: clock: qcom-rpmhcc: Add support for Nord SoCs
dt-bindings: clock: qcom: Document the Nord SoC TCSR Clock Controller
clk: qcom: gcc-x1e80100: Keep GCC USB QTB clock always ON
clk: qcom: Constify list of critical CBCR registers
clk: qcom: Constify qcom_cc_driver_data
clk: qcom: videocc-glymur: Constify qcom_cc_desc
clk: qcom: Add a driver for SM8750 GPU clocks
dt-bindings: clock: qcom: Add SM8750 GPU clocks
clk: qcom: ipq-cmn-pll: Add IPQ8074 SoC support
dt-bindings: clock: qcom: Add CMN PLL support for IPQ8074
clk: qcom: ipq-cmn-pll: Add IPQ6018 SoC support
dt-bindings: clock: qcom: Add CMN PLL support for IPQ6018
clk: qcom: gdsc: Fix error path on registration of multiple pm subdomains
dt-bindings: clock: qcom: Add missing power-domains property
clk: qcom: gcc-eliza: Enable FORCE_MEM_CORE_ON for UFS AXI PHY clock
clk: qcom: dispcc-sc7180: Add missing MDSS resets
...
* clk-round:
clk: divider: remove divider_round_rate() and divider_round_rate_parent()
clk: divider: remove divider_ro_round_rate_parent()
clk: remove round_rate() clk ops
clk: composite: convert from round_rate() to determine_rate()
clk: test: remove references to clk_ops.round_rate
* clk-sai:
clk: fsl-sai: Add MCLK generation support
clk: fsl-sai: Extract clock setup into fsl_sai_clk_register()
dt-bindings: clock: fsl-sai: Document clock-cells = <1> support
clk: fsl-sai: Add i.MX8M support with 8 byte register offset
clk: fsl-sai: Sort the headers
dt-bindings: clock: fsl-sai: Document i.MX8M support
* clk-cleanup:
clk: visconti: pll: initialize clk_init_data to zero
clk: xgene: Fix mapping leak in xgene_pllclk_init()
clk: Simplify clk_is_match()
clk: baikal-t1: Remove not-going-to-be-supported code for Baikal SoC
clk: mvebu: armada-37xx-periph: fix __iomem casts in structure init
clk: qoriq: avoid format string warning
Pull power utility updates from Len Brown:
"x86_energy_perf_policy:
- Initial SoC Slider support
turbostat:
- Display HT siblings in cpu# order
- Add Module-ID column
- Print Core-ID and APIC-ID in hex
- Fix misc bugs"
* tag 'power-utilities-2026.04.25' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux:
tools/power x86_energy_perf_policy: Version 2026.04.25
tools/power x86_energy_perf_policy.8: Document SoC Slider Options
tools/power x86_energy_perf_policy: Enhances SoC Slider related checks
tools/power turbostat: v2026.04.21
tools/power turbostat: Process HT siblings in CPU order
tools/power turbostat: Show module_id column
tools/power turbostat: Print core_id and apic_id in hex
tools/power turbostat: Cleanup print helper functions
tools/power turbostat: Fix --cpu-set 1 regression on HT systems
tools/power turbostat: Fix --cpu-set 0 regression on HT systems
tools/power turbostat: Fix unrecognized option '-P'
tools/power turbostat: Fix AMD RAPL regression on big systems
tools/power/x86: Add SOC slider and platform profile support
The fixdep hostprog may be built multiple times during a single build.
Once during the configuration phase and later during the regular phase.
As only the regular build phase respects CONFIG_WERROR / W=e, the
compiler flags might change between the phases, leading to rebuilds.
Example, the rebuilds will happen twice on each invocation of the build:
$ make allyesconfig prepare
make[1]: Entering directory '/tmp/deleteme'
HOSTCC scripts/basic/fixdep
#
# No change to .config
#
HOSTCC scripts/basic/fixdep
DESCEND objtool
INSTALL libsubcmd_headers
make[1]: Leaving directory '/tmp/deleteme'
Fix the compilation flags used for scripts/basic/ before
scripts/Makefile.warn is evaluated to stop CONFIG_WERROR / W=e
influencing the fixdep build to avoid the spurious rebuilds.
Fixes: 7ded7d37e5f5 ("scripts/Makefile.extrawarn: Respect CONFIG_WERROR / W=e for hostprogs")
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Link: https://patch.msgid.link/20260422-kbuild-scripts-basic-werror-v1-1-8c6912ff22e0@weissschuh.net
Signed-off-by: Nicolas Schier <nsc@kernel.org>
* clk-tenstorrent:
clk: tenstorrent: Add Atlantis clock controller driver
reset: tenstorrent: Add reset controller for Atlantis
dt-bindings: clk: tenstorrent: Add tenstorrent,atlantis-prcm-rcpu
* clk-rockchip:
clk: rockchip: rk3568: Add PCIe pipe clock gates
clk: rockchip: Add clock controller for the RV1103B
dt-bindings: clock: rockchip: Add RV1103B CRU support
* clk-imx:
clk: imx8mq: Correct the CSI PHY sels
clk: vf610: Add support for the Ethernet switch clocks
dt-bindings: clock: vf610: Add definitions for MTIP L2 switch
dt-bindings: clock: vf610: Drop VF610_CLK_END define
clk: vf610: Move VF610_CLK_END define to clk-vf610 driver
clk: imx: imx8-acm: fix flags for acm clocks
clk: imx: imx6q: Fix device node reference leak in of_assigned_ldb_sels()
clk: imx: imx6q: Fix device node reference leak in pll6_bypassed()
clk: imx: fracn-gppll: Add 477.4MHz support
clk: imx: fracn-gppll: Add 333.333333 MHz support
clk: imx: pll14xx: Use unsigned format specifier
dt-bindings: clock: imx6q[ul]-clock: add optional clock enet[1]_ref_pad
* clk-allwinner:
clk: sunxi-ng: sun55i-a523-r: Add missing r-spi module clock
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