[PATCH v2 1/3] perf tool: fix reading new topology attribute "core_cpus"

[Konstantin Khlebnikov]

Check access("devices/system/cpu/cpu%d/topology/core_cpus", F_OK) fails,
unless current directory is "/sys". Simply try read this file first.

Signed-off-by: Konstantin Khlebnikov <khlebni...@yandex-team.ru>
Fixes: 0ccdb8407a46 ("perf tools: Apply new CPU topology sysfs attributes")
---
 tools/perf/util/smt.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/smt.c b/tools/perf/util/smt.c
index 3b791ef2cd50..8481842e9edb 100644
--- a/tools/perf/util/smt.c
+++ b/tools/perf/util/smt.c
@@ -24,13 +24,13 @@ int smt_on(void)
 
                snprintf(fn, sizeof fn,
                        "devices/system/cpu/cpu%d/topology/core_cpus", cpu);
-               if (access(fn, F_OK) == -1) {
+               if (sysfs__read_str(fn, &str, &strlen) < 0) {
                        snprintf(fn, sizeof fn,
                                
"devices/system/cpu/cpu%d/topology/thread_siblings",
                                cpu);
+                       if (sysfs__read_str(fn, &str, &strlen) < 0)
+                               continue;
                }
-               if (sysfs__read_str(fn, &str, &strlen) < 0)
-                       continue;
                /* Entry is hex, but does not have 0x, so need custom parser */
                siblings = strtoull(str, NULL, 16);
                free(str);