linux-kernel - [PATCH 5.15 126/171] perf tools: Fix SMT detection fast read path

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Date:   Mon, 13 Dec 2021 10:30:41 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ian Rogers <irogers@...gle.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>, Jiri Olsa <jolsa@...hat.com>,
        John Garry <john.garry@...wei.com>,
        Kajol Jain <kjain@...ux.ibm.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Konstantin Khlebnikov <koct9i@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        Namhyung Kim <namhyung@...nel.org>,
        Paul Clarke <pc@...ibm.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Stephane Eranian <eranian@...gle.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 5.15 126/171] perf tools: Fix SMT detection fast read path

From: Ian Rogers <irogers@...gle.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@...gle.com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Andi Kleen <ak@...ux.intel.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: John Garry <john.garry@...wei.com>
Cc: Kajol Jain <kjain@...ux.ibm.com>
Cc: Kan Liang <kan.liang@...ux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@...il.com>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Paul Clarke <pc@...ibm.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Stephane Eranian <eranian@...gle.com>
Link: http://lore.kernel.org/lkml/20211124001231.3277836-2-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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);