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Filename Latest commit message Latest commit date
Steven Rostedt (Google) c0f7253376 tracing/histogram: Fix sorting on old "cpu" value
commit 1d1898f65616c4601208963c3376c1d828cbf2c7 upstream.

When trying to add a histogram against an event with the "cpu" field, it
was impossible due to "cpu" being a keyword to key off of the running CPU.
So to fix this, it was changed to "common_cpu" to match the other generic
fields (like "common_pid"). But since some scripts used "cpu" for keying
off of the CPU (for events that did not have "cpu" as a field, which is
most of them), a backward compatibility trick was added such that if "cpu"
was used as a key, and the event did not have "cpu" as a field name, then
it would fallback and switch over to "common_cpu".

This fix has a couple of subtle bugs. One was that when switching over to
"common_cpu", it did not change the field name, it just set a flag. But
the code still found a "cpu" field. The "cpu" field is used for filtering
and is returned when the event does not have a "cpu" field.

This was found by:

  # cd /sys/kernel/tracing
  # echo hist:key=cpu,pid:sort=cpu > events/sched/sched_wakeup/trigger
  # cat events/sched/sched_wakeup/hist

Which showed the histogram unsorted:

{ cpu:         19, pid:       1175 } hitcount:          1
{ cpu:          6, pid:        239 } hitcount:          2
{ cpu:         23, pid:       1186 } hitcount:         14
{ cpu:         12, pid:        249 } hitcount:          2
{ cpu:          3, pid:        994 } hitcount:          5

Instead of hard coding the "cpu" checks, take advantage of the fact that
trace_event_field_field() returns a special field for "cpu" and "CPU" if
the event does not have "cpu" as a field. This special field has the
"filter_type" of "FILTER_CPU". Check that to test if the returned field is
of the CPU type instead of doing the string compare.

Also, fix the sorting bug by testing for the hist_field flag of
HIST_FIELD_FL_CPU when setting up the sort routine. Otherwise it will use
the special CPU field to know what compare routine to use, and since that
special field does not have a size, it returns tracing_map_cmp_none.

Cc: stable@vger.kernel.org
Fixes: 1e3bac71c505 ("tracing/histogram: Rename "cpu" to "common_cpu"")
Reported-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-03-08 19:07:50 +01:00
arch ARM: 9182/1: mmu: fix returns from early_param() and __setup() functions 2022-03-08 19:07:49 +01:00
block block: Fix fsync always failed if once failed 2022-03-08 19:07:47 +01:00
certs
crypto
Documentation bpf: Add kconfig knob for disabling unpriv bpf by default 2022-02-16 12:52:49 +01:00
drivers HID: add mapping for KEY_ALL_APPLICATIONS 2022-03-08 19:07:50 +01:00
fs cifs: fix double free race when mount fails in cifs_get_root() 2022-03-08 19:07:45 +01:00
include HID: add mapping for KEY_ALL_APPLICATIONS 2022-03-08 19:07:50 +01:00
init bpf: Add kconfig knob for disabling unpriv bpf by default 2022-02-16 12:52:49 +01:00
ipc shm: extend forced shm destroy to support objects from several IPC nses 2021-12-01 09:23:35 +01:00
kernel tracing/histogram: Fix sorting on old "cpu" value 2022-03-08 19:07:50 +01:00
lib lib/iov_iter: initialize "flags" in new pipe_buffer 2022-02-23 11:59:59 +01:00
LICENSES
mm memfd: fix F_SEAL_WRITE after shmem huge page allocated 2022-03-08 19:07:49 +01:00
net nl80211: Handle nla_memdup failures in handle_nan_filter 2022-03-08 19:07:50 +01:00
samples
scripts kconfig: fix failing to generate auto.conf 2022-02-23 12:00:01 +01:00
security ima: Do not print policy rule with inactive LSM labels 2022-02-16 12:52:47 +01:00
sound ASoC: cs4265: Fix the duplicated control name 2022-03-08 19:07:49 +01:00
tools perf data: Fix double free in perf_session__delete() 2022-03-02 11:41:05 +01:00
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virt
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Makefile Linux 5.4.182 2022-03-02 11:41:18 +01:00
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.