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Steven Rostedt (VMware) 12ad0cb212 tracing: Use trace_clock_local() for looping in preemptirq_delay_test.c
The preemptirq_delay_test module is used for the ftrace selftest code that
tests the latency tracers. The problem is that it uses ktime for the delay
loop, and then checks the tracer to see if the delay loop is caught, but the
tracer uses trace_clock_local() which uses various different other clocks to
measure the latency. As ktime uses the clock cycles, and the code then
converts that to nanoseconds, it causes rounding errors, and the preemptirq
latency tests are failing due to being off by 1 (it expects to see a delay
of 500000 us, but the delay is only 499999 us). This is happening due to a
rounding error in the ktime (which is totally legit). The purpose of the
test is to see if it can catch the delay, not to test the accuracy between
trace_clock_local() and ktime_get(). Best to use apples to apples, and have
the delay loop use the same clock as the latency tracer does.

Cc: stable@vger.kernel.org
Fixes: f96e8577da ("lib: Add module for testing preemptoff/irqsoff latency tracers")
Acked-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2018-10-17 15:35:33 -04:00
arch xen: fixes for 4.19-rc5 2018-09-23 13:32:19 +02:00
block block: use nanosecond resolution for iostat 2018-09-21 20:26:59 -06:00
certs
crypto
Documentation This pull request is slightly bigger than usual at this stage, but 2018-09-21 16:21:42 +02:00
drivers - Fix Dialog DA9063 regulator constraints issue causing failure in probe 2018-09-23 17:19:27 +02:00
firmware
fs This pull request contains fixes for UBIFS: 2018-09-21 15:29:44 +02:00
include tracepoint: Fix tracepoint array element size mismatch 2018-10-17 15:35:29 -04:00
init
ipc
kernel tracing: Use trace_clock_local() for looping in preemptirq_delay_test.c 2018-10-17 15:35:33 -04:00
lib vsprintf: Fix off-by-one bug in bstr_printf() processing dereferenced pointers 2018-10-05 10:17:15 -04:00
LICENSES
mm mm: slowly shrink slabs with a relatively small number of objects 2018-09-20 22:01:11 +02:00
net net/ipv6: do not copy dst flags on rt init 2018-09-17 19:42:14 -07:00
samples
scripts
security
sound
tools Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-09-23 08:09:16 +02:00
usr
virt
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-09-23 08:10:12 +02:00
Makefile Linux 4.19-rc5 2018-09-23 19:15:18 +02:00
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.
See Documentation/00-INDEX for a list of what is contained in each file.

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.