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2160d6c8a1
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Tom Zanussi 2160d6c8a1 tools lib traceevent: Add proper KBUFFER_TYPE_TIME_STAMP handling 
Kernel commit dc4e2801d4 (ring-buffer: Redefine the unimplemented
RINGBUF_TYPE_TIME_STAMP) changed the way the ring buffer timestamps work
- after that commit the previously unimplemented RINGBUF_TYPE_TIME_STAMP
type causes the time delta to be used as a timestamp rather than a delta
to be added to the timestamp.

The trace-cmd code didn't get updated to handle this, so misinterprets
the event data for this case, which causes a cascade of errors,
including trace-report not being able to identify synthetic (or any
other) events generated by the histogram code (which uses TIME_STAMP
mode).  For example, the following triggers along with the trace-cmd
shown cause an UNKNOWN_EVENT error and trace-cmd report crash:

  # echo 'wakeup_latency  u64 lat pid_t pid char comm[16]' > /sys/kernel/debug/tracing/synthetic_events

  # echo 'hist:keys=pid:ts0=common_timestamp.usecs if comm=="ping"' > /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
  # echo 'hist:keys=next_pid:wakeup_lat=common_timestamp.usecs-$ts0:onmatch(sched.sched_wakeup).trace(wakeup_latency,$wakeup_lat,next_pid,next_comm) if next_comm=="ping"' > /sys/kernel/debug/tracing/events/sched/sched_switch/trigger
  # echo 'hist:keys=comm,pid,lat:wakeup_lat=lat:sort=lat' > /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/trigger

  # trace-cmd record -e wakeup_latency -e sched_wakeup -f comm==\"ping\" ping localhost -c 5

  # trace-cmd report
  CPU 0 is empty
  CPU 1 is empty
  CPU 2 is empty
  CPU 3 is empty
  CPU 5 is empty
  CPU 6 is empty
  CPU 7 is empty
  cpus=8
    ug! no event found for type 0
  [UNKNOWN TYPE 0]
    ug! no event found for type 11520
  Segmentation fault (core dumped)

After this patch we get the correct interpretation and the events are
shown properly:

  # trace-cmd report
  CPU 0 is empty
  CPU 1 is empty
  CPU 2 is empty
  CPU 3 is empty
  CPU 5 is empty
  CPU 6 is empty
  CPU 7 is empty
  cpus=8
          <idle>-0     [004] 23284.341392: sched_wakeup:         ping:12031 [120] success=1 CPU:004
          <idle>-0     [004] 23284.341464: wakeup_latency:       lat=58, pid=12031, comm=ping
          <idle>-0     [004] 23285.365303: sched_wakeup:         ping:12031 [120] success=1 CPU:004
          <idle>-0     [004] 23285.365382: wakeup_latency:       lat=64, pid=12031, comm=ping
          <idle>-0     [004] 23286.389290: sched_wakeup:         ping:12031 [120] success=1 CPU:004
          <idle>-0     [004] 23286.389378: wakeup_latency:       lat=72, pid=12031, comm=ping
          <idle>-0     [004] 23287.413213: sched_wakeup:         ping:12031 [120] success=1 CPU:004
          <idle>-0     [004] 23287.413291: wakeup_latency:       lat=64, pid=12031, comm=ping

Link: http://lkml.kernel.org/r/1567628224.13841.4.camel@kernel.org
Link: http://lore.kernel.org/linux-trace-devel/20200625100516.365338-3-tz.stoyanov@gmail.com

Signed-off-by: Tom Zanussi <zanussi@kernel.org>
[ Ported from trace-cmd.git ]
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: linux-trace-devel@vger.kernel.org
Link: http://lore.kernel.org/lkml/20200702185703.785094515@goodmis.org
Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2020-07-03 08:45:38 -03:00
arch m68k: mm: fix node memblock init 2020-06-29 23:58:05 +10:00
block block-5.8-2020-07-01 2020-07-02 15:13:51 -07:00
certs
crypto crypto: af_alg - fix use-after-free in af_alg_accept() due to bh_lock_sock() 2020-06-18 17:09:54 +10:00
Documentation Devicetree fixes for v5.8, take 2: 2020-07-02 22:46:05 -07:00
drivers tpmdd updates for Linux v5.8-rc4 2020-07-02 22:36:19 -07:00
fs Fixes for a umask bug on exported filesystems lacking ACL support, a 2020-07-02 20:35:33 -07:00
include block-5.8-2020-07-01 2020-07-02 15:13:51 -07:00
init Kbuild updates for v5.8 (2nd) 2020-06-13 13:29:16 -07:00
ipc mmap locking API: use coccinelle to convert mmap_sem rwsem call sites 2020-06-09 09:39:14 -07:00
kernel for-linus-2020-07-02 2020-07-02 22:40:06 -07:00
lib Peter Zijlstra says: 2020-06-28 09:42:47 -07:00
LICENSES
mm mm/memory_hotplug.c: fix false softlockup during pfn range removal 2020-06-26 00:27:38 -07:00
net Fixes for a umask bug on exported filesystems lacking ACL support, a 2020-07-02 20:35:33 -07:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-06-25 18:27:40 -07:00
scripts Devicetree fixes for v5.8, take 2: 2020-07-02 22:46:05 -07:00
security Two simple fixes for v5.8: 2020-06-30 12:21:53 -07:00
sound sound fixes for 5.8-rc3 2020-06-25 09:15:24 -07:00
tools tools lib traceevent: Add proper KBUFFER_TYPE_TIME_STAMP handling 2020-07-03 08:45:38 -03:00
usr
virt MIPS: 2020-06-12 11:05:52 -07:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore modpost: generate vmlinux.symvers and reuse it for the second modpost 2020-06-06 23:38:12 +09:00
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS Devicetree fixes for v5.8, take 2: 2020-07-02 22:46:05 -07:00
Makefile Linux 5.8-rc3 2020-06-28 15:00:24 -07:00
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.