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Thomas Richter 7b0131a022 perf stat: Handle different PMU names with common prefix 
commit ea1fa48c05 upstream.

On s390 the CPU Measurement Facility for counters now supports
2 PMUs named cpum_cf (CPU Measurement Facility for counters) and
cpum_cf_diag (CPU Measurement Facility for diagnostic counters)
for one and the same CPU.

Running command

 [root@s35lp76 perf]# ./perf stat -e tx_c_tend \
	 -- ~/mytests/cf-tx-events 1

 Measuring transactions
 TX_C_TABORT_NO_SPECIAL: 0 expected:0
 TX_C_TABORT_SPECIAL: 0 expected:0
 TX_C_TEND: 1 expected:1
 TX_NC_TABORT: 11 expected:11
 TX_NC_TEND: 1 expected:1

 Performance counter stats for '/root/mytests/cf-tx-events 1':

  2      tx_c_tend

      0.002120091 seconds time elapsed

      0.000121000 seconds user
      0.002127000 seconds sys

 [root@s35lp76 perf]#

displays output which is unexpected (and wrong):

  2      tx_c_tend

The test program definitely triggers only one transaction, as shown
in line 'TX_C_TEND: 1 expected:1'.

This is caused by the following call sequence:

pmu_lookup() scans and installs a PMU.
+--> pmu_aliases() parses all aliases in directory
		.../<pmu-name>/events/* which are file names.
     +--> pmu_aliases_parse() Read each file in directory and create
                      an new alias entry. This is done with
          +--> perf_pmu__new_alias() and
	       +--> __perf_pmu__new_alias() which also check for
	                   identical alias names.

After pmu_aliases() returns, a complete list of event names
for this pmu has been created. Now function

pmu_add_cpu_aliases()   is called to add the events listed in the json
|                       files to the alias list of the cpu.
+--> perf_pmu__find_map()  Returns a pointer to the json events.

Now function pmu_add_cpu_aliases() scans through all events listed
in the JSON files for this CPU.
Each json event pmu name is compared with the current PMU being
built up and if they mismatch, the json event is added to the
current PMUs alias list.
To avoid duplicate entries the following comparison is done:

	if (!is_arm_pmu_core(name)) {
	     pname = pe->pmu ? pe->pmu : "cpu";
	     if (strncmp(pname, name, strlen(pname)))
		     continue;
     }

The culprit is the strncmp() function.

Using current s390 PMU naming, the first PMU is 'cpum_cf'
and a long list of events is added, among them 'tx_c_tend'

When the second PMU named 'cpum_cf_diag' is added, only one event
named 'CF_DIAG' is added by the pmu_aliases()  function.

Now function pmu_add_cpu_aliases() is invoked for PMU 'cpum_cf_diag'.
Since the CPUID string is the same for both PMUs, json file events
for PMU named 'cpum_cf' are added to the PMU 'cpm_cf_diag'

This happens because the strncmp() actually compares:

     strncmp("cpum_cf", "cpum_cf_diag", 6);

The first parameter is the pmu name taken from the event in
the json file. The second parameter is the pmu name of the PMU
currently being built.
They are different, but the length of the compare only tests the
common prefix and this returns 0(true) when it should return false.

Now all events for PMU cpum_cf are added to the alias list for pmu
cpum_cf_diag.

Later on in function parse_events_add_pmu() the event 'tx_c_end' is
searched in all available PMUs and found twice, adding it two
times to the evsel_list global variable which is the root
of all events. This results in a counter value of 2 instead
of 1.

Output with this patch:

 [root@s35lp76 perf]# ./perf stat -e tx_c_tend \
			-- ~/mytests/cf-tx-events 1
 Measuring transactions
 TX_C_TABORT_NO_SPECIAL: 0 expected:0
 TX_C_TABORT_SPECIAL: 0 expected:0
 TX_C_TEND: 1 expected:1
 TX_NC_TABORT: 11 expected:11
 TX_NC_TEND: 1 expected:1

 Performance counter stats for '/root/mytests/cf-tx-events 1':

                  1      tx_c_tend

      0.001815365 seconds time elapsed

      0.000123000 seconds user
      0.001756000 seconds sys

 [root@s35lp76 perf]#

Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Reviewed-by: Hendrik Brueckner <brueckner@linux.ibm.com>
Reviewed-by: Sebastien Boisvert <sboisvert@gydle.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: stable@vger.kernel.org
Fixes: 292c34c102 ("perf pmu: Fix core PMU alias list for X86 platform")
Link: http://lkml.kernel.org/r/20181023151616.78193-1-tmricht@linux.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2018-11-21 09:19:19 +01:00
arch ARM: 8809/1: proc-v7: fix Thumb annotation of cpu_v7_hvc_switch_mm 2018-11-21 09:19:18 +01:00
block SCSI: fix queue cleanup race before queue initialization is done 2018-11-21 09:19:18 +01:00
certs export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR() 2018-08-22 23:21:44 +09:00
crypto crypto: speck - remove Speck 2018-11-13 11:08:46 -08:00
Documentation ovl: automatically enable redirect_dir on metacopy=on 2018-11-21 09:19:13 +01:00
drivers hwmon: (core) Fix double-free in __hwmon_device_register() 2018-11-21 09:19:19 +01:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs ocfs2: free up write context when direct IO failed 2018-11-21 09:19:18 +01:00
include mtd: nand: Fix nanddev_neraseblocks() 2018-11-21 09:19:19 +01:00
init Kbuild updates for v4.19 (2nd) 2018-08-25 13:40:38 -07:00
ipc ipc/shm.c: use ERR_CAST() for shm_lock() error return 2018-10-05 16:32:04 -07:00
kernel tracing/kprobes: Check the probe on unloaded module correctly 2018-11-21 09:19:09 +01:00
lib locking/lockdep: Fix debug_locks off performance problem 2018-11-13 11:08:20 -08:00
LICENSES LICENSES: Remove CC-BY-SA-4.0 license text 2018-10-18 11:28:50 +02:00
mm memory_hotplug: cond_resched in __remove_pages 2018-11-21 09:19:18 +01:00
net netfilter: conntrack: fix calculation of next bucket number in early_drop 2018-11-21 09:19:18 +01:00
samples samples: disable CONFIG_SAMPLES for UML 2018-10-11 02:15:46 +09:00
scripts Kbuild fixes for v4.19 (2nd) 2018-10-11 19:23:07 +02:00
security ima: open a new file instance if no read permissions 2018-11-13 11:08:46 -08:00
sound ASoC: sta32x: set ->component pointer in private struct 2018-11-13 11:08:42 -08:00
tools perf stat: Handle different PMU names with common prefix 2018-11-21 09:19:19 +01:00
usr initramfs: move gen_initramfs_list.sh from scripts/ to usr/ 2018-08-22 23:21:44 +09:00
virt KVM: arm64: Fix caching of host MDCR_EL2 value 2018-11-13 11:08:47 -08:00
.clang-format clang-format: Set IndentWrappedFunctionNames false 2018-08-01 18:38:51 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
.mailmap libnvdimm-for-4.19_misc 2018-08-25 18:13:10 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS 9p: remove Ron Minnich from MAINTAINERS 2018-08-17 16:20:26 -07:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS MAINTAINERS: Add an entry for the code of conduct 2018-10-22 07:33:36 +01:00
Makefile Linux 4.19.2 2018-11-13 11:09:00 -08:00
README Docs: Added a pointer to the formatted docs to README 2018-03-21 09:02:53 -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.
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.