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Filename Latest commit message Latest commit date
Paul E. McKenney cda27a2c6d rcu: Don't deboost before reporting expedited quiescent state
commit 10c535787436d62ea28156a4b91365fd89b5a432 upstream.

Currently rcu_preempt_deferred_qs_irqrestore() releases rnp->boost_mtx
before reporting the expedited quiescent state.  Under heavy real-time
load, this can result in this function being preempted before the
quiescent state is reported, which can in turn prevent the expedited grace
period from completing.  Tim Murray reports that the resulting expedited
grace periods can take hundreds of milliseconds and even more than one
second, when they should normally complete in less than a millisecond.

This was fine given that there were no particular response-time
constraints for synchronize_rcu_expedited(), as it was designed
for throughput rather than latency.  However, some users now need
sub-100-millisecond response-time constratints.

This patch therefore follows Neeraj's suggestion (seconded by Tim and
by Uladzislau Rezki) of simply reversing the two operations.

Reported-by: Tim Murray <timmurray@google.com>
Reported-by: Joel Fernandes <joelaf@google.com>
Reported-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Reviewed-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Tested-by: Tim Murray <timmurray@google.com>
Cc: Todd Kjos <tkjos@google.com>
Cc: Sandeep Patil <sspatil@google.com>
Cc: <stable@vger.kernel.org> # 5.4.x
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-03-28 08:46:48 +02:00
arch ACPI / x86: Work around broken XSDT on Advantech DAC-BJ01 board 2022-03-28 08:46:47 +02:00
block block: Fix fsync always failed if once failed 2022-03-08 19:07:47 +01:00
certs certs: Trigger creation of RSA module signing key if it's not an RSA key 2021-09-15 09:47:29 +02:00
crypto crypto: pcrypt - Delay write to padata->info 2021-11-17 09:48:40 +01:00
Documentation x86/speculation: Update link to AMD speculation whitepaper 2022-03-11 11:22:37 +01:00
drivers crypto: qat - disable registration of algorithms 2022-03-28 08:46:47 +02:00
fs nfsd: Containerise filecache laundrette 2022-03-28 08:46:43 +02:00
include esp: Fix possible buffer overflow in ESP transformation 2022-03-28 08:46:44 +02:00
init bpf: Add kconfig knob for disabling unpriv bpf by default 2022-02-16 12:52:49 +01:00
ipc shm: extend forced shm destroy to support objects from several IPC nses 2021-12-01 09:23:35 +01:00
kernel rcu: Don't deboost before reporting expedited quiescent state 2022-03-28 08:46:48 +02:00
lib ARM: 9178/1: fix unmet dependency on BITREVERSE for HAVE_ARCH_BITREVERSE 2022-03-19 13:40:16 +01:00
LICENSES
mm memfd: fix F_SEAL_WRITE after shmem huge page allocated 2022-03-08 19:07:49 +01:00
net netfilter: nf_tables: initialize registers in nft_do_chain() 2022-03-28 08:46:47 +02:00
samples samples/kretprobes: Fix return value if register_kretprobe() failed 2021-11-17 09:48:39 +01:00
scripts kconfig: fix failing to generate auto.conf 2022-02-23 12:00:01 +01:00
security ima: Do not print policy rule with inactive LSM labels 2022-02-16 12:52:47 +01:00
sound ALSA: hda/realtek: Add quirk for ASUS GA402 2022-03-28 08:46:46 +02:00
tools Revert "selftests/bpf: Add test for bpf_timer overwriting crash" 2022-03-23 09:12:08 +01:00
usr
virt KVM: arm64: Allow SMCCC_ARCH_WORKAROUND_3 to be discovered and migrated 2022-03-19 13:40:15 +01:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
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COPYING
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Kconfig
MAINTAINERS
Makefile Linux 5.4.187 2022-03-23 09:12:08 +01:00
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.