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Juri Lelli 9a68fa0ebb sched/features: Fix hrtick reprogramming 
[ Upstream commit 156ec6f42b ]

Hung tasks and RCU stall cases were reported on systems which were not
100% busy. Investigation of such unexpected cases (no sign of potential
starvation caused by tasks hogging the system) pointed out that the
periodic sched tick timer wasn't serviced anymore after a certain point
and that caused all machinery that depends on it (timers, RCU, etc.) to
stop working as well. This issues was however only reproducible if
HRTICK was enabled.

Looking at core dumps it was found that the rbtree of the hrtimer base
used also for the hrtick was corrupted (i.e. next as seen from the base
root and actual leftmost obtained by traversing the tree are different).
Same base is also used for periodic tick hrtimer, which might get "lost"
if the rbtree gets corrupted.

Much alike what described in commit 1f71addd34 ("tick/sched: Do not
mess with an enqueued hrtimer") there is a race window between
hrtimer_set_expires() in hrtick_start and hrtimer_start_expires() in
__hrtick_restart() in which the former might be operating on an already
queued hrtick hrtimer, which might lead to corruption of the base.

Use hrtick_start() (which removes the timer before enqueuing it back) to
ensure hrtick hrtimer reprogramming is entirely guarded by the base
lock, so that no race conditions can occur.

Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20210208073554.14629-2-juri.lelli@redhat.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-03-07 12:34:13 +01:00
arch parisc: Bump 64-bit IRQ stack size to 64 KB 2021-03-07 12:34:13 +01:00
block blk-settings: align max_sectors on "logical_block_size" boundary 2021-03-04 11:38:22 +01:00
certs certs: Fix blacklist flag type confusion 2021-03-04 11:37:59 +01:00
crypto crypto: tcrypt - avoid signed overflow in byte count 2021-03-07 12:34:11 +01:00
Documentation dt-bindings: net: btusb: DT fix s/interrupt-name/interrupt-names/ 2021-03-07 12:34:08 +01:00
drivers nvme-tcp: add clean action for failed reconnection 2021-03-07 12:34:12 +01:00
fs btrfs: fix error handling in commit_fs_roots 2021-03-07 12:34:13 +01:00
include Bluetooth: Add new HCI_QUIRK_NO_SUSPEND_NOTIFIER quirk 2021-03-07 12:34:10 +01:00
init kgdb: fix to kill breakpoints on initmem after boot 2021-03-04 11:38:46 +01:00
ipc ipc: adjust proc_ipc_sem_dointvec definition to match prototype 2020-09-05 12:14:29 -07:00
kernel sched/features: Fix hrtick reprogramming 2021-03-07 12:34:13 +01:00
lib udp: fix skb_copy_and_csum_datagram with odd segment sizes 2021-02-17 11:02:28 +01:00
LICENSES LICENSES/deprecated: add Zlib license text 2020-09-16 14:33:49 +02:00
mm mm/hugetlb.c: fix unnecessary address expansion of pmd sharing 2021-03-07 12:34:06 +01:00
net Bluetooth: Fix null pointer dereference in amp_read_loc_assoc_final_data 2021-03-07 12:34:10 +01:00
samples watch_queue: Drop references to /dev/watch_queue 2021-03-04 11:37:59 +01:00
scripts scripts/recordmcount.pl: support big endian for ARCH sh 2021-02-26 10:13:02 +01:00
security tomoyo: ignore data race while checking quota 2021-03-07 12:34:05 +01:00
sound ASoC: Intel: sof_sdw: detect DMIC number based on mach params 2021-03-07 12:34:13 +01:00
tools wireguard: selftests: test multiple parallel streams 2021-03-04 11:38:47 +01:00
usr Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 13:29:39 -07:00
virt KVM: Use kvm_pfn_t for local PFN variable in hva_to_pfn_remapped() 2021-02-26 10:13:01 +01:00
.clang-format RDMA 5.10 pull request 2020-10-17 11:18:18 -07:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: docs: ignore sphinx_*/ directories 2020-09-10 10:44:31 -06:00
.mailmap mailmap: add two more addresses of Uwe Kleine-König 2020-12-06 10:19:07 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Jason Cooper to CREDITS 2020-11-30 10:20:34 +01:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-12-10 15:30:13 -08:00
Makefile Linux 5.10.20 2021-03-04 11:38:47 +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.