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Nicholas Piggin 9664c5b908 lazy tlb: fix hotplug exit race with MMU_LAZY_TLB_SHOOTDOWN
CPU unplug first calls __cpu_disable(), and that's where powerpc calls
cleanup_cpu_mmu_context(), which clears this CPU from mm_cpumask() of all
mms in the system.

However this CPU may still be using a lazy tlb mm, and its mm_cpumask bit
will be cleared from it.  The CPU does not switch away from the lazy tlb
mm until arch_cpu_idle_dead() calls idle_task_exit().

If that user mm exits in this window, it will not be subject to the lazy
tlb mm shootdown and may be freed while in use as a lazy mm by the CPU
that is being unplugged.

cleanup_cpu_mmu_context() could be moved later, but it looks better to
move the lazy tlb mm switching earlier.  The problem with doing the lazy
mm switching in idle_task_exit() is explained in commit bf2c59fce4
("sched/core: Fix illegal RCU from offline CPUs"), which added a wart to
switch away from the mm but leave it set in active_mm to be cleaned up
later.

So instead, switch away from the lazy tlb mm at sched_cpu_wait_empty(),
which is the last hotplug state before teardown
(CPUHP_AP_SCHED_WAIT_EMPTY).  This CPU will never switch to a user thread
from this point, so it has no chance to pick up a new lazy tlb mm.  This
removes the lazy tlb mm handling wart in CPU unplug.

With this, idle_task_exit() is not needed anymore and can be cleaned up. 
This leaves the prototype alone, to be cleaned after this change.

herton: took the suggestions from https://lore.kernel.org/all/87jzvyprsw.ffs@tglx/
and made adjustments on the initial patch proposed by Nicholas.

Link: https://lkml.kernel.org/r/20230524060455.147699-1-npiggin@gmail.com
Link: https://lore.kernel.org/all/20230525205253.E2FAEC433EF@smtp.kernel.org/
Link: https://lkml.kernel.org/r/20241104142318.3295663-1-herton@redhat.com
Fixes: 2655421ae6 ("lazy tlb: shoot lazies, non-refcounting lazy tlb mm reference handling scheme")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Herton R. Krzesinski <herton@redhat.com>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-12-18 19:50:37 -08:00
arch mm: introduce cpu_icache_is_aliasing() across all architectures 2024-12-18 19:04:43 -08:00
block block: Fix potential deadlock while freezing queue and acquiring sysfs_lock 2024-12-13 10:51:58 -07:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: rsassa-pkcs1 - Copy source data for SG list 2024-12-10 13:34:05 +08:00
Documentation docs: tmpfs: drop 'fadvise()' from the documentation 2024-12-18 19:50:32 -08:00
drivers zram: fix uninitialized ZRAM not releasing backing device 2024-12-18 19:04:44 -08:00
fs ocfs2: fix slab-use-after-free due to dangling pointer dqi_priv 2024-12-18 19:49:59 -08:00
include lazy tlb: fix hotplug exit race with MMU_LAZY_TLB_SHOOTDOWN 2024-12-18 19:50:37 -08:00
init - The series "resource: A couple of cleanups" from Andy Shevchenko 2024-11-25 16:09:48 -08:00
io_uring io_uring/rsrc: don't put/free empty buffers 2024-12-12 08:01:52 -07:00
ipc - The series "resource: A couple of cleanups" from Andy Shevchenko 2024-11-25 16:09:48 -08:00
kernel lazy tlb: fix hotplug exit race with MMU_LAZY_TLB_SHOOTDOWN 2024-12-18 19:50:37 -08:00
lib maple_tree: only root node could be deficient 2024-12-18 19:50:37 -08:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm mm-swap_cgroup-allocate-swap_cgroup-map-using-vcalloc-fix 2024-12-18 19:50:36 -08:00
net BPF fixes: 2024-12-14 12:58:14 -08:00
rust rust: kbuild: set bindgen's Rust target version 2024-12-10 01:06:10 +01:00
samples BPF fixes: 2024-12-06 15:07:48 -08:00
scripts A single fix for a docs-build regression caused by the EXPORT_SYMBOL_NS() 2024-12-13 09:46:02 -08:00
security Including fixes from can and netfilter. 2024-12-05 10:25:06 -08:00
sound ASoC: Fixes for v6.13 2024-12-12 14:49:35 +01:00
tools selftest/mm: remove seal_elf 2024-12-18 19:50:34 -08:00
usr initramfs: shorten cmd_initfs in usr/Makefile 2024-07-16 01:07:52 +09:00
virt VFIO updates for v6.13 2024-11-27 12:57:03 -08:00
.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: enable Clippy's check-private-items 2024-10-07 21:39:57 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.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 updates for v6.13 2024-11-30 13:41:50 -08:00
.mailmap mailmap: modify the entry for Mathieu Othacehe 2024-12-18 19:49:58 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS cgroup: Changes for v6.13 2024-11-20 09:54:49 -08:00
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 block-6.13-20241213 2024-12-13 15:10:59 -08:00
Makefile Linux 6.13-rc3 2024-12-15 15:58:23 -08:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

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.