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Frederic Weisbecker 0836f94040 rcu/exp: Mark current CPU as exp-QS in IPI loop second pass 
[ Upstream commit 81f6d49cce ]

Expedited RCU grace periods invoke sync_rcu_exp_select_node_cpus(), which
takes two passes over the leaf rcu_node structure's CPUs.  The first
pass gathers up the current CPU and CPUs that are in dynticks idle mode.
The workqueue will report a quiescent state on their behalf later.
The second pass sends IPIs to the rest of the CPUs, but excludes the
current CPU, incorrectly assuming it has been included in the first
pass's list of CPUs.

Unfortunately the current CPU may have changed between the first and
second pass, due to the fact that the various rcu_node structures'
->lock fields have been dropped, thus momentarily enabling preemption.
This means that if the second pass's CPU was not on the first pass's
list, it will be ignored completely.  There will be no IPI sent to
it, and there will be no reporting of quiescent states on its behalf.
Unfortunately, the expedited grace period will nevertheless be waiting
for that CPU to report a quiescent state, but with that CPU having no
reason to believe that such a report is needed.

The result will be an expedited grace period stall.

Fix this by no longer excluding the current CPU from consideration during
the second pass.

Fixes: b9ad4d6ed1 ("rcu: Avoid self-IPI in sync_rcu_exp_select_node_cpus()")
Reviewed-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Uladzislau Rezki <urezki@gmail.com>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Joel Fernandes <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-01-27 10:53:55 +01:00
arch arm64: clear_page() shouldn't use DC ZVA when DCZID_EL0.DZP == 1 2022-01-27 10:53:54 +01:00
block iocost: Fix divide-by-zero on donation from low hweight cgroup 2021-12-22 09:30:57 +01:00
certs
crypto
Documentation bpf: Add kconfig knob for disabling unpriv bpf by default 2022-01-05 12:40:34 +01:00
drivers drm/msm/dp: displayPort driver need algorithm rational 2022-01-27 10:53:55 +01:00
fs fs: dlm: fix build with CONFIG_IPV6 disabled 2022-01-27 10:53:49 +01:00
include bpf: Disallow BPF_LOG_KERNEL log level for bpf(BPF_BTF_LOAD) 2022-01-27 10:53:54 +01:00
init bpf: Add kconfig knob for disabling unpriv bpf by default 2022-01-05 12:40:34 +01:00
ipc shm: extend forced shm destroy to support objects from several IPC nses 2021-12-01 09:19:10 +01:00
kernel rcu/exp: Mark current CPU as exp-QS in IPI loop second pass 2022-01-27 10:53:55 +01:00
lib siphash: use _unaligned version by default 2021-12-08 09:03:23 +01:00
LICENSES
mm shmem: fix a race between shmem_unused_huge_shrink and shmem_evict_inode 2022-01-27 10:53:44 +01:00
net netfilter: bridge: add support for pppoe filtering 2022-01-27 10:53:52 +01:00
samples ftrace/samples: Add missing prototypes direct functions 2022-01-11 15:25:00 +01:00
scripts recordmcount.pl: fix typo in s390 mcount regex 2022-01-05 12:40:29 +01:00
security selinux: initialize proto variable in selinux_ip_postroute_compat() 2022-01-05 12:40:30 +01:00
sound ALSA: hda/realtek: Re-order quirk entries for Lenovo 2022-01-20 09:17:51 +01:00
tools tools/nolibc: fix incorrect truncation of exit code 2022-01-27 10:53:42 +01:00
usr
virt KVM: downgrade two BUG_ONs to WARN_ON_ONCE 2021-12-22 09:30:50 +01:00
.clang-format
.cocciconfig
.get_maintainer.ignore
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CREDITS
Kbuild
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MAINTAINERS MAINTAINERS: adjust GCC PLUGINS after gcc-plugin.sh removal 2021-12-14 11:32:46 +01:00
Makefile Linux 5.10.93 2022-01-20 09:17:52 +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.