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Josh Don 1e116c18e3 Revert "sched/fair: Make sure to try to detach at least one movable task" 
commit 2feab2492d upstream.

This reverts commit b0defa7ae0.

b0defa7ae0 changed the load balancing logic to ignore env.max_loop if
all tasks examined to that point were pinned. The goal of the patch was
to make it more likely to be able to detach a task buried in a long list
of pinned tasks. However, this has the unfortunate side effect of
creating an O(n) iteration in detach_tasks(), as we now must fully
iterate every task on a cpu if all or most are pinned. Since this load
balance code is done with rq lock held, and often in softirq context, it
is very easy to trigger hard lockups. We observed such hard lockups with
a user who affined O(10k) threads to a single cpu.

When I discussed this with Vincent he initially suggested that we keep
the limit on the number of tasks to detach, but increase the number of
tasks we can search. However, after some back and forth on the mailing
list, he recommended we instead revert the original patch, as it seems
likely no one was actually getting hit by the original issue.

Fixes: b0defa7ae0 ("sched/fair: Make sure to try to detach at least one movable task")
Signed-off-by: Josh Don <joshdon@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20240620214450.316280-1-joshdon@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2024-07-18 13:21:17 +02:00
arch ARM: davinci: Convert comma to semicolon 2024-07-18 13:21:16 +02:00
block block/ioctl: prefer different overflow check 2024-06-27 13:49:01 +02:00
certs certs: Reference revocation list for all keyrings 2023-08-17 20:12:41 +00:00
crypto crypto: aead,cipher - zeroize key buffer after use 2024-07-11 12:49:04 +02:00
Documentation cifs: fix setting SecurityFlags to true 2024-07-18 13:21:17 +02:00
drivers octeontx2-af: fix issue with IPv4 match for RSS 2024-07-18 13:21:17 +02:00
fs cifs: fix setting SecurityFlags to true 2024-07-18 13:21:17 +02:00
include bpf: Fix too early release of tcx_entry 2024-07-18 13:21:12 +02:00
init smp: Provide 'setup_max_cpus' definition on UP too 2024-06-16 13:47:49 +02:00
io_uring io_uring/rsrc: fix incorrect assignment of iter->nr_segs in io_import_fixed 2024-06-27 13:49:10 +02:00
ipc Add x86 shadow stack support 2023-08-31 12:20:12 -07:00
kernel Revert "sched/fair: Make sure to try to detach at least one movable task" 2024-07-18 13:21:17 +02:00
lib kunit: Fix timeout message 2024-07-11 12:49:08 +02:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm Revert "mm/writeback: fix possible divide-by-zero in wb_dirty_limits(), again" 2024-07-11 12:49:16 +02:00
net net, sunrpc: Remap EPERM in case of connection failure in xs_tcp_setup_socket 2024-07-18 13:21:14 +02:00
rust rust: kernel: require Send for Module implementations 2024-05-17 12:01:56 +02:00
samples work around gcc bugs with 'asm goto' with outputs 2024-02-23 09:24:47 +01:00
scripts kbuild: fix short log for AS in link-vmlinux.sh 2024-07-11 12:49:21 +02:00
security ima: Avoid blocking in RCU read-side critical section 2024-07-11 12:49:18 +02:00
sound ASoC: SOF: Intel: hda: fix null deref on system suspend entry 2024-07-18 13:21:15 +02:00
tools selftests: make order checking verbose in msg_zerocopy selftest 2024-07-11 12:49:14 +02:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt KVM: Fix a data race on last_boosted_vcpu in kvm_vcpu_on_spin() 2024-06-27 13:49:11 +02:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.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: 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 COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
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 pwm: Rename pwm_apply_state() to pwm_apply_might_sleep() 2024-06-12 11:12:24 +02:00
Makefile Linux 6.6.40 2024-07-15 09:24:53 +02:00
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.