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Tejun Heo 5f93225dc9 Revert "kernfs: convert kernfs_idr_lock to an irq safe raw spinlock" 
commit e3977e0609 upstream.

This reverts commit dad3fb67ca1cbef87ce700e83a55835e5921ce8a.

The commit converted kernfs_idr_lock to an IRQ-safe raw_spinlock because it
could be acquired while holding an rq lock through bpf_cgroup_from_id().
However, kernfs_idr_lock is held while doing GPF_NOWAIT allocations which
involves acquiring an non-IRQ-safe and non-raw lock leading to the following
lockdep warning:

  =============================
  [ BUG: Invalid wait context ]
  6.7.0-rc5-kzm9g-00251-g655022a45b1c #578 Not tainted
  -----------------------------
  swapper/0/0 is trying to lock:
  dfbcd488 (&c->lock){....}-{3:3}, at: local_lock_acquire+0x0/0xa4
  other info that might help us debug this:
  context-{5:5}
  2 locks held by swapper/0/0:
   #0: dfbc9c60 (lock){+.+.}-{3:3}, at: local_lock_acquire+0x0/0xa4
   #1: c0c012a8 (kernfs_idr_lock){....}-{2:2}, at: __kernfs_new_node.constprop.0+0x68/0x258
  stack backtrace:
  CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.7.0-rc5-kzm9g-00251-g655022a45b1c #578
  Hardware name: Generic SH73A0 (Flattened Device Tree)
   unwind_backtrace from show_stack+0x10/0x14
   show_stack from dump_stack_lvl+0x68/0x90
   dump_stack_lvl from __lock_acquire+0x3cc/0x168c
   __lock_acquire from lock_acquire+0x274/0x30c
   lock_acquire from local_lock_acquire+0x28/0xa4
   local_lock_acquire from ___slab_alloc+0x234/0x8a8
   ___slab_alloc from __slab_alloc.constprop.0+0x30/0x44
   __slab_alloc.constprop.0 from kmem_cache_alloc+0x7c/0x148
   kmem_cache_alloc from radix_tree_node_alloc.constprop.0+0x44/0xdc
   radix_tree_node_alloc.constprop.0 from idr_get_free+0x110/0x2b8
   idr_get_free from idr_alloc_u32+0x9c/0x108
   idr_alloc_u32 from idr_alloc_cyclic+0x50/0xb8
   idr_alloc_cyclic from __kernfs_new_node.constprop.0+0x88/0x258
   __kernfs_new_node.constprop.0 from kernfs_create_root+0xbc/0x154
   kernfs_create_root from sysfs_init+0x18/0x5c
   sysfs_init from mnt_init+0xc4/0x220
   mnt_init from vfs_caches_init+0x6c/0x88
   vfs_caches_init from start_kernel+0x474/0x528
   start_kernel from 0x0

Let's rever the commit. It's undesirable to spread out raw spinlock usage
anyway and the problem can be solved by protecting the lookup path with RCU
instead.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Andrea Righi <andrea.righi@canonical.com>
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: http://lkml.kernel.org/r/CAMuHMdV=AKt+mwY7svEq5gFPx41LoSQZ_USME5_MEdWQze13ww@mail.gmail.com
Link: https://lore.kernel.org/r/20240109214828.252092-2-tj@kernel.org
Tested-by: Andrea Righi <andrea.righi@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-01-25 15:35:41 -08:00
arch ARM: davinci: always select CONFIG_CPU_ARM926T 2024-01-25 15:35:30 -08:00
block blk-cgroup: fix rcu lockdep warning in blkg_lookup() 2024-01-25 15:35:30 -08:00
certs certs: Reference revocation list for all keyrings 2023-08-17 20:12:41 +00:00
crypto crypto: scomp - fix req->dst buffer overflow 2024-01-25 15:35:18 -08:00
Documentation media: dt-bindings: media: rkisp1: Fix the port description for the parallel interface 2024-01-25 15:35:35 -08:00
drivers class: fix use-after-free in class_register() 2024-01-25 15:35:41 -08:00
fs Revert "kernfs: convert kernfs_idr_lock to an irq safe raw spinlock" 2024-01-25 15:35:41 -08:00
include gpiolib: provide gpio_device_find() 2024-01-25 15:35:39 -08:00
init proc: sysctl: prevent aliased sysctls from getting passed to init 2023-11-28 17:19:57 +00:00
io_uring io_uring: use fget/fput consistently 2024-01-20 11:51:38 +01:00
ipc Add x86 shadow stack support 2023-08-31 12:20:12 -07:00
kernel bpf: Use c->unit_size to select target cache during free 2024-01-25 15:35:28 -08:00
lib kunit: debugfs: Fix unchecked dereference in debugfs_print_results() 2024-01-25 15:35:15 -08:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm/memory_hotplug: fix memmap_on_memory sysfs value retrieval 2024-01-20 11:51:49 +01:00
net ip6_tunnel: fix NEXTHDR_FRAGMENT handling in ip6_tnl_parse_tlv_enc_lim() 2024-01-25 15:35:30 -08:00
rust rust: docs: fix logo replacement 2023-10-19 16:40:00 +02:00
samples vfio/mtty: Overhaul mtty interrupt handling 2024-01-10 17:16:55 +01:00
scripts scripts/decode_stacktrace.sh: optionally use LLVM utilities 2024-01-20 11:51:49 +01:00
security selinux: Fix error priority for bind with AF_UNSPEC on PF_INET6 socket 2024-01-25 15:35:15 -08:00
sound ALSA: scarlett2: Add clamp() in scarlett2_mixer_ctl_put() 2024-01-25 15:35:39 -08:00
tools kselftest/alsa - conf: Stringify the printed errno in sysfs_get() 2024-01-25 15:35:40 -08:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt ARM: 2023-09-07 13:52:20 -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 kbuild: rpm-pkg: rename binkernel.spec to kernel.spec 2023-07-25 00:59:33 +09:00
.mailmap 20 hotfixes. 12 are cc:stable and the remainder address post-6.5 issues 2023-10-24 09:52:16 -10:00
.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
MAINTAINERS Char/Misc driver fixes for 6.6-final 2023-10-28 07:51:27 -10:00
Makefile Linux 6.6.13 2024-01-20 11:51:49 +01:00
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.