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Gavin Shan b9792abb76 drivers/base/memory: Avoid overhead from for_each_present_section_nr() 
for_each_present_section_nr() was introduced to add_boot_memory_block()
by commit 61659efdb3 ("drivers/base/memory: improve add_boot_memory_block()").
It causes unnecessary overhead when the present sections are really
sparse. next_present_section_nr() called by the macro to find the next
present section, which is far away from the spanning sections in the
specified block. Too much time consumed by next_present_section_nr()
in this case, which can lead to softlockup as observed by Aditya Gupta
on IBM Power10 machine.

  watchdog: BUG: soft lockup - CPU#248 stuck for 22s! [swapper/248:1]
  Modules linked in:
  CPU: 248 UID: 0 PID: 1 Comm: swapper/248 Not tainted 6.15.0-rc1-next-20250408 #1 VOLUNTARY
  Hardware name: 9105-22A POWER10 (raw) 0x800200 opal:v7.1-107-gfda75d121942 PowerNV
  NIP:  c00000000209218c LR: c000000002092204 CTR: 0000000000000000
  REGS: c00040000418fa30 TRAP: 0900   Not tainted  (6.15.0-rc1-next-20250408)
  MSR:  9000000002009033 <SF,HV,VEC,EE,ME,IR,DR,RI,LE>  CR: 28000428  XER: 00000000
  CFAR: 0000000000000000 IRQMASK: 0
  GPR00: c000000002092204 c00040000418fcd0 c000000001b08100 0000000000000040
  GPR04: 0000000000013e00 c000c03ffebabb00 0000000000c03fff c000400fff587f80
  GPR08: 0000000000000000 00000000001196f7 0000000000000000 0000000028000428
  GPR12: 0000000000000000 c000000002e80000 c00000000001007c 0000000000000000
  GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
  GPR20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
  GPR24: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
  GPR28: c000000002df7f70 0000000000013dc0 c0000000011dd898 0000000008000000
  NIP [c00000000209218c] memory_dev_init+0x114/0x1e0
  LR [c000000002092204] memory_dev_init+0x18c/0x1e0
  Call Trace:
  [c00040000418fcd0] [c000000002092204] memory_dev_init+0x18c/0x1e0 (unreliable)
  [c00040000418fd50] [c000000002091348] driver_init+0x78/0xa4
  [c00040000418fd70] [c0000000020063ac] kernel_init_freeable+0x22c/0x370
  [c00040000418fde0] [c0000000000100a8] kernel_init+0x34/0x25c
  [c00040000418fe50] [c00000000000cd94] ret_from_kernel_user_thread+0x14/0x1c

Avoid the overhead by folding for_each_present_section_nr() to the outer
loop. add_boot_memory_block() is dropped after that.

Fixes: 61659efdb3 ("drivers/base/memory: improve add_boot_memory_block()")
Closes: https://lore.kernel.org/linux-mm/20250409180344.477916-1-adityag@linux.ibm.com
Reported-by: Aditya Gupta <adityag@linux.ibm.com>
Signed-off-by: Gavin Shan <gshan@redhat.com>
Acked-by: Oscar Salvador <osalvador@suse.de>
Tested-by: Aditya Gupta <adityag@linux.ibm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20250410125110.1232329-1-gshan@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2025-04-15 18:19:49 +02:00
arch A set of final cleanups for the timer subsystem: 2025-04-06 08:35:37 -07:00
block treewide: Switch/rename to timer_delete[_sync]() 2025-04-05 10:30:12 +02:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto This push fixes reverts the multibuffer hash testing as it is buggy. 2025-04-02 09:14:59 -07:00
Documentation A set of final cleanups for the timer subsystem: 2025-04-06 08:35:37 -07:00
drivers drivers/base/memory: Avoid overhead from for_each_present_section_nr() 2025-04-15 18:19:49 +02:00
fs Miscellaneous scheduler fixes/updates: 2025-04-06 10:44:58 -07:00
include device property: Add a note to the fwnode.h 2025-04-15 18:10:57 +02:00
init Miscellaneous scheduler fixes/updates: 2025-04-06 10:44:58 -07:00
io_uring io_uring: always do atomic put from iowq 2025-04-03 08:31:57 -06:00
ipc treewide: const qualify ctl_tables where applicable 2025-01-28 13:48:37 +01:00
kernel Fix a perf events time accounting bug. 2025-04-06 10:48:12 -07:00
lib Kbuild updates for v6.15 2025-04-05 15:46:50 -07:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm Disable SLUB_TINY for build testing 2025-04-06 10:00:04 -07:00
net treewide: Switch/rename to timer_delete[_sync]() 2025-04-05 10:30:12 +02:00
rust rust: firmware: Use ffi::c_char type in FwFunc 2025-04-14 14:13:23 +02:00
samples treewide: Switch/rename to timer_delete[_sync]() 2025-04-05 10:30:12 +02:00
scripts Disable SLUB_TINY for build testing 2025-04-06 10:00:04 -07:00
security mseal sysmap: kernel config and header change 2025-04-01 15:17:14 -07:00
sound soundwire fix for 6.15-rc1 2025-04-06 12:04:53 -07:00
tools tools/include: make uapi/linux/types.h usable from assembly 2025-04-06 12:55:31 -07:00
usr kbuild: hdrcheck: fix cross build with clang 2025-03-05 04:06:45 +09:00
virt ARM: 2025-03-25 14:22:07 -07:00
.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 2025-01-10 00:17:25 +01:00
.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: Create intermediate vmlinux build with relocations preserved 2025-03-17 00:29:50 +09:00
.mailmap mailmap: add an entry for Nicolas Schier 2025-04-01 15:20:45 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING
CREDITS Including fixes from netfilter. 2025-04-04 09:15:35 -07:00
Kbuild drm: ensure drm headers are self-contained and pass kernel-doc 2025-02-12 10:44:43 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS drivers/base: Add myself as auxiliary bus reviewer 2025-04-15 18:10:42 +02:00
Makefile Linux 6.15-rc1 2025-04-06 13:11:33 -07:00
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.