Patch "perf header: Fixup reading of HEADER_NRCPUS feature" has been added to the 4.1-stable tree

Patch "perf header: Fixup reading of HEADER_NRCPUS feature" has been added to the 4.1-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    perf header: Fixup reading of HEADER_NRCPUS feature

to the 4.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     perf-header-fixup-reading-of-header_nrcpus-feature.patch
and it can be found in the queue-4.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From caa470475d9b59eeff093ae650800d34612c4379 Mon Sep 17 00:00:00 2001
From: Arnaldo Carvalho de Melo <acme@redhat.com>
Date: Fri, 11 Sep 2015 12:36:12 -0300
Subject: perf header: Fixup reading of HEADER_NRCPUS feature

From: Arnaldo Carvalho de Melo <acme@redhat.com>

commit caa470475d9b59eeff093ae650800d34612c4379 upstream.

The original patch introducing this header wrote the number of CPUs available
and online in one order and then swapped those values when reading, fix it.

Before:

  # perf record usleep 1
  # perf report --header-only | grep 'nrcpus \(online\|avail\)'
  # nrcpus online : 4
  # nrcpus avail : 4
  # echo 0 > /sys/devices/system/cpu/cpu2/online
  # perf record usleep 1
  # perf report --header-only | grep 'nrcpus \(online\|avail\)'
  # nrcpus online : 4
  # nrcpus avail : 3
  # echo 0 > /sys/devices/system/cpu/cpu1/online
  # perf record usleep 1
  # perf report --header-only | grep 'nrcpus \(online\|avail\)'
  # nrcpus online : 4
  # nrcpus avail : 2

After the fix, bringing back the CPUs online:

  # perf report --header-only | grep 'nrcpus \(online\|avail\)'
  # nrcpus online : 2
  # nrcpus avail : 4
  # echo 1 > /sys/devices/system/cpu/cpu2/online
  # perf record usleep 1
  # perf report --header-only | grep 'nrcpus \(online\|avail\)'
  # nrcpus online : 3
  # nrcpus avail : 4
  # echo 1 > /sys/devices/system/cpu/cpu1/online
  # perf record usleep 1
  # perf report --header-only | grep 'nrcpus \(online\|avail\)'
  # nrcpus online : 4
  # nrcpus avail : 4

Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Wang Nan <wangnan0@huawei.com>
Fixes: fbe96f29ce4b ("perf tools: Make perf.data more self-descriptive (v8)")
Link: http://lkml.kernel.org/r/20150911153323.GP23511@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 tools/perf/util/header.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -1426,7 +1426,7 @@ static int process_nrcpus(struct perf_fi
 	if (ph->needs_swap)
 		nr = bswap_32(nr);
 
-	ph->env.nr_cpus_online = nr;
+	ph->env.nr_cpus_avail = nr;
 
 	ret = readn(fd, &nr, sizeof(nr));
 	if (ret != sizeof(nr))
@@ -1435,7 +1435,7 @@ static int process_nrcpus(struct perf_fi
 	if (ph->needs_swap)
 		nr = bswap_32(nr);
 
-	ph->env.nr_cpus_avail = nr;
+	ph->env.nr_cpus_online = nr;
 	return 0;
 }
 


Patches currently in stable-queue which might be from acme@redhat.com are

queue-4.1/perf-tools-add-empty-build-files-for-architectures-lacking-them.patch
queue-4.1/perf-stat-get-correct-cpu-id-for-print_aggr.patch
queue-4.1/perf-tools-fix-copying-of-proc-kcore.patch
queue-4.1/perf-hists-update-the-column-width-for-the-srcline-sort-key.patch
queue-4.1/perf-header-fixup-reading-of-header_nrcpus-feature.patch