[PATCH 5.10 090/132] perf tools: Fix SMT detection fast read path

Greg Kroah-Hartman
2021-12-13T09:58:56Z

From: Ian Rogers <irogers@google.com>

commit 4ffbe87e2d5b53bcb0213d8650bbe70bf942de6a upstream.

sysfs__read_int() returns 0 on success, and so the fast read path was
always failing.

Fixes: bb629484d924118e ("perf tools: Simplify checking if SMT is active.")
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: John Garry <john.garry@huawei.com>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Clarke <pc@us.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20211124001231.3277836-2-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
tools/perf/util/smt.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/tools/perf/util/smt.c
+++ b/tools/perf/util/smt.c
@@ -15,7 +15,7 @@ int smt_on(void)
if (cached)
return cached_result;

- if (sysfs__read_int("devices/system/cpu/smt/active", &cached_result) > 0)
+ if (sysfs__read_int("devices/system/cpu/smt/active", &cached_result) >= 0)
goto done;

ncpu = sysconf(_SC_NPROCESSORS_CONF);