kernel/linux
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ synced 2026-09-28 19:20:30 +00:00
Code Issues Releases Packages Activity
No description
1,140,983 commits 116 branches 5,780 tags 5.6 GiB
  • C 96.9%
  • Assembly 0.9%
  • Rust 0.6%
  • Shell 0.6%
  • Python 0.5%
  • Other 0.3%
Find a file
Petr Pavlu 14f4d81f64 module: Don't wait for GOING modules 
commit 0254127ab9 upstream.

During a system boot, it can happen that the kernel receives a burst of
requests to insert the same module but loading it eventually fails
during its init call. For instance, udev can make a request to insert
a frequency module for each individual CPU when another frequency module
is already loaded which causes the init function of the new module to
return an error.

Since commit 6e6de3dee5 ("kernel/module.c: Only return -EEXIST for
modules that have finished loading"), the kernel waits for modules in
MODULE_STATE_GOING state to finish unloading before making another
attempt to load the same module.

This creates unnecessary work in the described scenario and delays the
boot. In the worst case, it can prevent udev from loading drivers for
other devices and might cause timeouts of services waiting on them and
subsequently a failed boot.

This patch attempts a different solution for the problem 6e6de3dee5
was trying to solve. Rather than waiting for the unloading to complete,
it returns a different error code (-EBUSY) for modules in the GOING
state. This should avoid the error situation that was described in
6e6de3dee5 (user space attempting to load a dependent module because
the -EEXIST error code would suggest to user space that the first module
had been loaded successfully), while avoiding the delay situation too.

This has been tested on linux-next since December 2022 and passes
all kmod selftests except test 0009 with module compression enabled
but it has been confirmed that this issue has existed and has gone
unnoticed since prior to this commit and can also be reproduced without
module compression with a simple usleep(5000000) on tools/modprobe.c [0].
These failures are caused by hitting the kernel mod_concurrent_max and can
happen either due to a self inflicted kernel module auto-loead DoS somehow
or on a system with large CPU count and each CPU count incorrectly triggering
many module auto-loads. Both of those issues need to be fixed in-kernel.

[0] https://lore.kernel.org/all/Y9A4fiobL6IHp%2F%2FP@bombadil.infradead.org/

Fixes: 6e6de3dee5 ("kernel/module.c: Only return -EEXIST for modules that have finished loading")
Co-developed-by: Martin Wilck <mwilck@suse.com>
Signed-off-by: Martin Wilck <mwilck@suse.com>
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
Cc: stable@vger.kernel.org
Reviewed-by: Petr Mladek <pmladek@suse.com>
[mcgrof: enhance commit log with testing and kmod test result interpretation ]
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2023-02-01 08:34:37 +01:00
arch arm64: efi: Account for the EFI runtime stack in stack unwinder 2023-02-01 08:34:35 +01:00
block block: mq-deadline: Rename deadline_is_seq_writes() 2023-01-24 07:24:44 +01:00
certs certs: make system keyring depend on built-in x509 parser 2022-09-24 04:31:18 +09:00
crypto crypto: tcrypt - Fix multibuffer skcipher speed test mem leak 2022-12-31 13:32:34 +01:00
Documentation docs: Fix path paste-o for /sys/kernel/warn_count 2023-01-24 07:24:41 +01:00
drivers scsi: hpsa: Fix allocation size for scsi_host_alloc() 2023-02-01 08:34:36 +01:00
fs nfsd: don't free files unconditionally in __nfsd_file_cache_purge 2023-02-01 08:34:36 +01:00
include wifi: mac80211: Proper mark iTXQs for resumption 2023-02-01 08:34:35 +01:00
init gcc: disable -Warray-bounds for gcc-11 too 2023-01-14 10:33:43 +01:00
io_uring io_uring/msg_ring: fix remote queue to disabled ring 2023-02-01 08:34:35 +01:00
ipc ipc: fix memory leak in init_mqueue_fs() 2022-12-31 13:32:01 +01:00
kernel module: Don't wait for GOING modules 2023-02-01 08:34:37 +01:00
lib lockref: stop doing cpu_relax in the cmpxchg loop 2023-02-01 08:34:34 +01:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm panic: Consolidate open-coded panic_on_warn checks 2023-01-24 07:24:41 +01:00
net wifi: mac80211: Fix iTXQ AMPDU fragmentation handling 2023-02-01 08:34:36 +01:00
rust Kbuild: add Rust support 2022-09-28 09:02:20 +02:00
samples samples: vfio-mdev: Fix missing pci_disable_device() in mdpy_fb_probe() 2022-12-31 13:32:42 +01:00
scripts - Handle different output of readelf on different distros running 2022-11-27 12:08:17 -08:00
security tomoyo: fix broken dependency on *.conf.default 2023-02-01 08:34:06 +01:00
sound ASoC: fsl-asoc-card: Fix naming of AC'97 CODEC widgets 2023-02-01 08:34:31 +01:00
tools Revert "selftests/bpf: check null propagation only neither reg is PTR_TO_BTF_ID" 2023-02-01 08:34:34 +01:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt kvm/vfio: Fix potential deadlock on vfio group_lock 2023-02-01 08:34:36 +01:00
.clang-format inet: ping: use hlist_nulls rcu iterator during lookup 2022-12-01 12:42:46 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore Kbuild: add Rust support 2022-09-28 09:02:20 +02:00
.mailmap 9 hotfixes. 6 for MM, 3 for other areas. Four of these patches address 2022-12-10 17:10:52 -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 MAINTAINERS: Remove Michal Marek from Kbuild maintainers 2022-11-16 14:53:00 +09:00
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 panic: Expose "warn_count" to sysfs 2023-01-24 07:24:41 +01:00
Makefile kbuild: fix 'make modules' error when CONFIG_DEBUG_INFO_BTF_MODULES=y 2023-02-01 08:34:08 +01:00
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.