[PATCH] perf test: Fix failing test case Session Topology

[Thomas Richter <tmricht@linux.ibm.com>]

Test case 37 Session topology fails on s390. I bisected this to

commit 05be17eed774 ("tool api fs: Correctly encode errno for read/write open failures")

When perf tool is invoked, it builds the perf.data file using the
following function sequence:

  #0  has_die_topology () at util/cputopo.c:223
  #1  cpu_topology__new () at util/cputopo.c:302
  ....
  #9  0x00000000012a5c7a in perf_session__write_header (...)
  	at util/header.c:3774
  #10 0x00000000011ccd64 in session_write_header (...)
	at tests/topology.c:53
  #11 0x00000000011cde9c in test__session_topology (...)
	at tests/topology.c:215
  #12 0x0000000001190276 in start_test (...)

The function has_die_topology() checks for existence of sys file
/sys/devices/system/cpu/cpu0/topology/die_cpus_list
which does not exist on s390. This function returns false and
information for all CPU dies is omitted in the
perf data file section HEADER_CPU_TOPOLOGY.

Later on the test case reads the perf.data file back using
functions.

  check_cpu_topology()
  +--> perf_session__new()

the missing CPU die information in the HEADER_CPU_TOPOLOGY section
causes the id_die field set to 0 in the session->header.env.cpu[0].

Later on when the test case result is verified, the functions

  test__session_topology()
  +--> check_cpu_topology()
       +--> aggr_cpu_id__cpu()
	    +--> aggr_cpu_id__core()
	         +--> aggr_cpu_id__cluster()
	              +--> aggr_cpu_id__die()
	                   +--> cpu__get_topology_int()
	                        +--> sysfs__read_int()

Function aggr_cpu_id__die() reads the die_id from the CPU's
/sys/devices/system/cpu/cpu0/topology/die_id file entry.
This file does not exist and function
sysfs__read_int() now returns error number -2 (ENOENT).
Structure member id.die has value of -2.

This new return value of -2 bypasses this check in function
aggr_cpu_id__die():

	/* There is no die_id on legacy system. */
        if (die == -1)
                die = 0;
and the test verification fails in:

  TEST_ASSERT_VAL("Cpu map - Die ID doesn't match",
	session->header.env.cpu[cpu.cpu].die_id == id.die)

Output before:
 # ./perf test -F 37
 37: Session topology               : FAILED!
 #

Output after:
 # ./perf test -F 37
 37: Session topology               : Ok
 #

Fixes: 05be17eed774 ("tool api fs: Correctly encode errno for read/write open failures")
Cc: Ian Rogers <irogers@google.com>
Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
---
 tools/perf/util/cpumap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/cpumap.c b/tools/perf/util/cpumap.c
index 27094211edd8..05ced29385f7 100644
--- a/tools/perf/util/cpumap.c
+++ b/tools/perf/util/cpumap.c
@@ -293,7 +293,7 @@ struct aggr_cpu_id aggr_cpu_id__die(struct perf_cpu cpu, void *data)
 
 	die = cpu__get_die_id(cpu);
 	/* There is no die_id on legacy system. */
-	if (die == -1)
+	if (die <= -1)
 		die = 0;
 
 	/*
-- 
2.48.1