Paul E. McKenney
dba9cda5aa
clocksource: Retry clock read if long delays detected ...
[ Upstream commit db3a34e17433de2390eb80d436970edcebd0ca3e ]
When the clocksource watchdog marks a clock as unstable, this might be due
to that clock being unstable or it might be due to delays that happen to
occur between the reads of the two clocks. Yes, interrupts are disabled
across those two reads, but there are no shortage of things that can delay
interrupts-disabled regions of code ranging from SMI handlers to vCPU
preemption. It would be good to have some indication as to why the clock
was marked unstable.
Therefore, re-read the watchdog clock on either side of the read from the
clock under test. If the watchdog clock shows an excessive time delta
between its pair of reads, the reads are retried.
The maximum number of retries is specified by a new kernel boot parameter
clocksource.max_cswd_read_retries, which defaults to three, that is, up to
four reads, one initial and up to three retries. If more than one retry
was required, a message is printed on the console (the occasional single
retry is expected behavior, especially in guest OSes). If the maximum
number of retries is exceeded, the clock under test will be marked
unstable. However, the probability of this happening due to various sorts
of delays is quite small. In addition, the reason (clock-read delays) for
the unstable marking will be apparent.
Reported-by: Chris Mason <clm@fb.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Feng Tang <feng.tang@intel.com>
Link: https://lore.kernel.org/r/20210527190124.440372-1-paulmck@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-07-14 16:53:18 +02:00
evm: Refuse EVM_ALLOW_METADATA_WRITES only if an HMAC key is loaded
2021-07-14 16:53:08 +02:00
clocksource: Retry clock read if long delays detected
2021-07-14 16:53:18 +02:00
ARM: 9012/1: move device tree mapping out of linear region
2021-05-19 10:08:32 +02:00
arm64: errata: Hide CTR_EL0.DIC on systems affected by Neoverse-N1 #1542419
2020-04-29 16:32:56 +02:00
docs: block: null_blk: enhance document style
2019-09-11 16:04:22 -06:00
XArray: add xas_split
2021-06-10 13:37:14 +02:00
Documentation: cpufreq: Update policy notifier documentation
2019-09-02 22:44:05 +02:00
Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6
2019-09-18 12:11:14 -07:00
mm, page_owner: decouple freeing stack trace from debug_pagealloc
2019-10-14 15:04:00 -07:00
dt-bindings: net: ethernet-controller: fix typo in NVMEM
2021-04-14 08:24:18 +02:00
ata: make qc_prep return ata_completion_errors
2020-10-01 13:18:26 +02:00
fbdev: fix numbering of fbcon options
2020-02-24 08:36:42 +01:00
It's a somewhat calmer cycle for docs this time, as the churn of the mass
2019-09-17 16:22:26 -07:00
sysfs: Add sysfs_emit and sysfs_emit_at to format sysfs output
2021-03-07 12:20:48 +01:00
Documentation: ACPI: DSD: Convert LED documentation to ReST
2019-08-20 23:53:46 +02:00
Documentation: fpga: dfl: add descriptions for virtualization and new interfaces.
2019-09-03 19:35:42 -07:00
Merge drm/drm-next into drm-intel-next-queued
2019-08-22 00:10:36 -07:00
hwmon: (max31790) Fix pwmX_enable attributes
2021-07-14 16:53:14 +02:00
Documentation/infiniband: update name of some functions
2019-09-13 16:55:55 -03:00
kbuild: support LLVM=1 to switch the default tools to Clang/LLVM
2020-08-26 10:40:47 +02:00
docs: Add documentation for Symbol Namespaces
2019-09-10 10:30:49 +02:00
doc 🔒 remove reference to clever use of read-write lock
2019-09-14 01:53:27 -06:00
media: videodev2.h: RGB BT2020 and HSV are always full range
2020-11-05 11:43:15 +01:00
Main MIPS changes for v5.4:
2019-09-22 09:30:30 -07:00
can: j1939: swap addr and pgn in the send example
2020-11-18 19:20:19 +01:00
Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net
2019-08-27 14:23:31 -07:00
Merge branches 'pm-opp', 'pm-qos', 'acpi-pm', 'pm-domains' and 'pm-tools'
2019-09-17 09:49:19 +02:00
docs: powerpc: Add missing documentation reference
2019-09-17 23:59:34 +10:00
Documentation/process: Add fallthrough pseudo-keyword
2019-10-11 09:26:05 -07:00
It's a somewhat calmer cycle for docs this time, as the churn of the mass
2019-09-17 16:22:26 -07:00
Documentation/s390: remove outdated debugging390 documentation
2019-08-21 12:41:43 +02:00
scsi: smartpqi: Update attribute name to driver_version
2020-01-17 19:48:27 +01:00
Merge branch 'next-integrity' of git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity
2019-09-27 19:37:27 -07:00
ALSA: hda/realtek - Remove now-unnecessary XPS 13 headphone noise fixups
2020-04-17 10:50:08 +02:00
tweewide: Fix most Shebang lines
2021-05-22 11:38:30 +02:00
tweewide: Fix most Shebang lines
2021-05-22 11:38:30 +02:00
tweewide: Fix most Shebang lines
2021-05-22 11:38:30 +02:00
doc: arm64: fix grammar dtb placed in no attributes region
2019-09-06 08:44:34 -06:00
USB: rio500: Remove Rio 500 kernel driver
2019-10-04 10:53:36 +02:00
Documentation: seccomp: Fix user notification documentation
2021-06-03 08:59:03 +02:00
KVM: arm64: Reject VM creation when the default IPA size is unsupported
2021-03-17 17:03:57 +01:00
mm/slub: clarify verification reporting
2021-06-23 14:41:30 +02:00
linux-watchdog 5.4-rc1 tag
2019-09-27 11:17:38 -07:00
x86/CPU/AMD: Save AMD NodeId as cpu_die_id
2020-12-30 11:51:47 +01:00
xtensa: fix TLBTEMP area placement
2020-11-24 13:29:22 +01:00
linkage: Introduce new macros for assembler symbols
2020-11-10 12:37:24 +01:00
dma-mapping: remove dma_release_declared_memory
2019-09-04 11:13:19 +02:00
linkage: Introduce new macros for assembler symbols
2020-11-10 12:37:24 +01:00
lib/lzo: fix ambiguous encoding bug in lzo-rle
2020-06-17 16:40:28 +02:00
padata: allocate workqueue internally
2019-09-13 21:15:39 +10:00
dba9cda5aa
