From: Ian Rogers <irogers@google.com>

Date: Tue, 23 Nov 2021 16:12:29 -0800

Subject: perf tools: Fix SMT detection fast read path

Git-commit: 4ffbe87e2d5b53bcb0213d8650bbe70bf942de6a

Patch-mainline: v5.16-rc5

References: git-fixes

​

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: Tony Jones <tonyj@suse.de>

---

 tools/perf/util/smt.c | 2 +-

 1 file changed, 1 insertion(+), 1 deletion(-)

​

diff --git a/tools/perf/util/smt.c b/tools/perf/util/smt.c

index 20bacd5972ad..34f1b1b1176c 100644

--- 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);

​

​