[PATCH 3.4 32/92] perf header: Fixup reading of HEADER_NRCPUS feature

lizf
2016-04-18T10:48:51Z

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

3.4.112-rc1 review patch. If anyone has any objections, please let me know.

------------------

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>
[lizf: Backported to 3.4: fix it by saving values in an array and then print
it in reverse order]
Signed-off-by: Zefan Li <lizefan@huawei.com>
---
tools/perf/util/header.c | 22 ++++++++--------------
1 file changed, 8 insertions(+), 14 deletions(-)

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index c0b70c6..5a4482c 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -1060,25 +1060,19 @@ static void print_cpudesc(struct perf_header *ph, int fd, FILE *fp)
static void print_nrcpus(struct perf_header *ph, int fd, FILE *fp)
{
ssize_t ret;
- u32 nr;
+ u32 nr[2];

ret = read(fd, &nr, sizeof(nr));
if (ret != (ssize_t)sizeof(nr))
- nr = -1; /* interpreted as error */
+ nr[0] = nr[1] = -1; /* interpreted as error */

- if (ph->needs_swap)
- nr = bswap_32(nr);
-
- fprintf(fp, "# nrcpus online : %u\n", nr);
-
- ret = read(fd, &nr, sizeof(nr));
- if (ret != (ssize_t)sizeof(nr))
- nr = -1; /* interpreted as error */
-
- if (ph->needs_swap)
- nr = bswap_32(nr);
+ if (ph->needs_swap) {
+ nr[0] = bswap_32(nr[0]);
+ nr[1] = bswap_32(nr[1]);
+ }

- fprintf(fp, "# nrcpus avail : %u\n", nr);
+ fprintf(fp, "# nrcpus online : %u\n", nr[1]);
+ fprintf(fp, "# nrcpus avail : %u\n", nr[0]);
}

static void print_version(struct perf_header *ph, int fd, FILE *fp)
--
1.9.1