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Jane Chu 59cd6535e7 mm/hugetlb: fix copy_hugetlb_page_range() to use ->pt_share_count commit `14967a9c7d` upstream. commit `59d9094df3` ("mm: hugetlb: independent PMD page table shared count") introduced ->pt_share_count dedicated to hugetlb PMD share count tracking, but omitted fixing copy_hugetlb_page_range(), leaving the function relying on page_count() for tracking that no longer works. When lazy page table copy for hugetlb is disabled, that is, revert commit `bcd51a3c67` ("hugetlb: lazy page table copies in fork()") fork()'ing with hugetlb PMD sharing quickly lockup - [ 239.446559] watchdog: BUG: soft lockup - CPU#75 stuck for 27s! [ 239.446611] RIP: 0010:native_queued_spin_lock_slowpath+0x7e/0x2e0 [ 239.446631] Call Trace: [ 239.446633] <TASK> [ 239.446636] _raw_spin_lock+0x3f/0x60 [ 239.446639] copy_hugetlb_page_range+0x258/0xb50 [ 239.446645] copy_page_range+0x22b/0x2c0 [ 239.446651] dup_mmap+0x3e2/0x770 [ 239.446654] dup_mm.constprop.0+0x5e/0x230 [ 239.446657] copy_process+0xd17/0x1760 [ 239.446660] kernel_clone+0xc0/0x3e0 [ 239.446661] __do_sys_clone+0x65/0xa0 [ 239.446664] do_syscall_64+0x82/0x930 [ 239.446668] ? count_memcg_events+0xd2/0x190 [ 239.446671] ? syscall_trace_enter+0x14e/0x1f0 [ 239.446676] ? syscall_exit_work+0x118/0x150 [ 239.446677] ? arch_exit_to_user_mode_prepare.constprop.0+0x9/0xb0 [ 239.446681] ? clear_bhb_loop+0x30/0x80 [ 239.446684] ? clear_bhb_loop+0x30/0x80 [ 239.446686] entry_SYSCALL_64_after_hwframe+0x76/0x7e There are two options to resolve the potential latent issue: 1. warn against PMD sharing in copy_hugetlb_page_range(), 2. fix it. This patch opts for the second option. While at it, simplify the comment, the details are not actually relevant anymore. Link: https://lkml.kernel.org/r/20250916004520.1604530-1-jane.chu@oracle.com Fixes: `59d9094df3` ("mm: hugetlb: independent PMD page table shared count") Signed-off-by: Jane Chu <jane.chu@oracle.com> Reviewed-by: Harry Yoo <harry.yoo@oracle.com> Acked-by: Oscar Salvador <osalvador@suse.de> Acked-by: David Hildenbrand <david@redhat.com> Cc: Jann Horn <jannh@google.com> Cc: Liu Shixin <liushixin2@huawei.com> Cc: Muchun Song <muchun.song@linux.dev> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> [ David: We don't have ptdesc and the wrappers, so work directly on the page->pt_share_count. CONFIG_HUGETLB_PMD_PAGE_TABLE_SHARING is still called CONFIG_ARCH_WANT_HUGE_PMD_SHARE. ] Signed-off-by: David Hildenbrand (Arm) <david@kernel.org> 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	drm/radeon: apply state adjust rules to some additional HAINAN vairants	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
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.