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Hugh Dickins ee40d543e9 mm/pagewalk: fix bootstopping regression from extra pte_unmap() 
Mikhail reports early-6.6-based Fedora Rawhide not booting: "rcu_preempt
detected expedited stalls", minutes wait, and then hung_task splat while
kworker trying to synchronize_rcu_expedited().  Nothing logged to disk.

He bisected to my 6.6 a349d72fd9 ("mm/pgtable: add rcu_read_lock() and
rcu_read_unlock()s"): but the one to blame is my 6.5 commit to fix the
espfix "bad pmd" warnings when booting x86_64 with CONFIG_EFI_PGT_DUMP=y.

Gaah, that added an "addr >= TASK_SIZE" check to avoid pte_offset_map(),
but failed to add the equivalent check when choosing to pte_unmap().

It's not a problem on 6.5 (for different reasons, it's harmless on both
64-bit and 32-bit), but becomes a bootstopper on 6.6 with the unbalanced
rcu_read_unlock() - RCU has a WARN_ON_ONCE for that, but it would have
scrolled off Mikhail's console too quickly.

Reported-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Closes: https://lore.kernel.org/linux-mm/CABXGCsNi8Tiv5zUPNXr6UJw6qV1VdaBEfGqEAMkkXE3QPvZuAQ@mail.gmail.com/
Fixes: 8b1cb4a2e8 ("mm/pagewalk: fix EFI_PGT_DUMP of espfix area")
Fixes: a349d72fd9 ("mm/pgtable: add rcu_read_lock() and rcu_read_unlock()s")
Signed-off-by: Hugh Dickins <hughd@google.com>
Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2023-09-02 08:39:21 -07:00
arch * Mark all Skylake CPUs as vulnerable to GDS 2023-09-01 16:40:19 -07:00
block for-6.6/block-2023-08-28 2023-08-29 20:21:42 -07:00
certs certs: Reference revocation list for all keyrings 2023-08-17 20:12:41 +00:00
crypto This update includes the following changes: 2023-08-29 11:23:29 -07:00
Documentation IOMMU Updates for Linux v6.6 2023-09-01 16:54:25 -07:00
drivers fbdev/g364fb: fix build failure with mips 2023-09-02 08:18:40 -07:00
fs Tracing updates for 6.6: 2023-09-01 16:34:25 -07:00
include IOMMU Updates for Linux v6.6 2023-09-01 16:54:25 -07:00
init workqueue: Changes for v6.6 2023-09-01 16:06:32 -07:00
io_uring for-6.6/io_uring-2023-08-28 2023-08-29 20:11:33 -07:00
ipc Add x86 shadow stack support 2023-08-31 12:20:12 -07:00
kernel cgroup: fix build when CGROUP_SCHED is not enabled 2023-09-02 08:27:17 -07:00
lib percpu: changes for v6.6 2023-09-01 15:44:45 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm/pagewalk: fix bootstopping regression from extra pte_unmap() 2023-09-02 08:39:21 -07:00
net TTY/Serial driver changes for 6.6-rc1 2023-09-01 09:38:00 -07:00
rust Documentation work keeps chugging along; stuff for 6.6 includes: 2023-08-30 20:05:42 -07:00
samples VFIO updates for v6.6-rc1 2023-08-30 20:36:01 -07:00
scripts Documentation work keeps chugging along; stuff for 6.6 includes: 2023-08-30 20:05:42 -07:00
security Smack updates for v6.6. Two minor fixes. 2023-08-30 09:28:07 -07:00
sound TTY/Serial driver changes for 6.6-rc1 2023-09-01 09:38:00 -07:00
tools Tracing updates for 6.6: 2023-09-01 16:34:25 -07:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt VFIO updates for v6.6-rc1 2023-08-30 20:36:01 -07:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Revert ".gitignore: ignore *.cover and *.mbx" 2023-07-04 15:05:12 -07:00
.mailmap for-linus-2023083101 2023-09-01 12:31:44 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING
CREDITS USB: Remove Wireless USB and UWB documentation 2023-08-09 14:17:32 +02:00
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 IOMMU Updates for Linux v6.6 2023-09-01 16:54:25 -07:00
Makefile Rust changes for v6.6 2023-08-29 08:19:46 -07:00
README

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.