linux-kernel - [tip:perf/urgent] perf pmu: Fix core PMU alias list for X86 platform

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Date:   Wed, 25 Apr 2018 22:56:17 -0700
From:   tip-bot for Kan Liang <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     jolsa@...hat.com, will.deacon@....com, peterz@...radead.org,
        ak@...ux.intel.com, agustinv@...eaurora.org, tglx@...utronix.de,
        kan.liang@...ux.intel.com, namhyung@...nel.org,
        linux-kernel@...r.kernel.org, ganapatrao.kulkarni@...ium.com,
        yao.jin@...ux.intel.com, acme@...hat.com, hpa@...or.com,
        zhangshaokun@...ilicon.com, mingo@...nel.org
Subject: [tip:perf/urgent] perf pmu: Fix core PMU alias list for X86
 platform

Commit-ID:  292c34c10249c64a70def442f0d977bf9d466ed7
Gitweb:     https://git.kernel.org/tip/292c34c10249c64a70def442f0d977bf9d466ed7
Author:     Kan Liang <kan.liang@...ux.intel.com>
AuthorDate: Tue, 24 Apr 2018 11:20:10 -0700
Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Tue, 24 Apr 2018 16:02:29 -0300

perf pmu: Fix core PMU alias list for X86 platform

When counting uncore event with alias, core event is mistakenly
involved, for example:

  perf stat --no-merge -e "unc_m_cas_count.all" -C0  sleep 1

  Performance counter stats for 'CPU(s) 0':

                 0      unc_m_cas_count.all [uncore_imc_4]
                 0      unc_m_cas_count.all [uncore_imc_2]
                 0      unc_m_cas_count.all [uncore_imc_0]
           153,640      unc_m_cas_count.all [cpu]
                 0      unc_m_cas_count.all [uncore_imc_5]
            25,026      unc_m_cas_count.all [uncore_imc_3]
                 0      unc_m_cas_count.all [uncore_imc_1]

       1.001447890 seconds time elapsed

The reason is that current implementation doesn't check PMU name of a
event when adding its alias into the alias list for core PMU. The
uncore event aliases are mistakenly added.

This bug was introduced in:
  commit 14b22ae028de ("perf pmu: Add helper function is_pmu_core to
  detect PMU CORE devices")

Checking the PMU name for all PMUs on X86 and other architectures except
ARM.
There is no behavior change for ARM.

Signed-off-by: Kan Liang <kan.liang@...ux.intel.com>
Tested-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Agustin Vega-Frias <agustinv@...eaurora.org>
Cc: Andi Kleen <ak@...ux.intel.com>
Cc: Ganapatrao Kulkarni <ganapatrao.kulkarni@...ium.com>
Cc: Jin Yao <yao.jin@...ux.intel.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Shaokun Zhang <zhangshaokun@...ilicon.com>
Cc: Will Deacon <will.deacon@....com>
Fixes: 14b22ae028de ("perf pmu: Add helper function is_pmu_core to detect PMU CORE devices")
Link: http://lkml.kernel.org/r/1524594014-79243-1-git-send-email-kan.liang@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/pmu.c | 20 +++++++-------------
 1 file changed, 7 insertions(+), 13 deletions(-)

diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index af4bedf4cf98..d2fb597c9a8c 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -539,9 +539,10 @@ static bool pmu_is_uncore(const char *name)
 
 /*
  *  PMU CORE devices have different name other than cpu in sysfs on some
- *  platforms. looking for possible sysfs files to identify as core device.
+ *  platforms.
+ *  Looking for possible sysfs files to identify the arm core device.
  */
-static int is_pmu_core(const char *name)
+static int is_arm_pmu_core(const char *name)
 {
 	struct stat st;
 	char path[PATH_MAX];
@@ -550,12 +551,6 @@ static int is_pmu_core(const char *name)
 	if (!sysfs)
 		return 0;
 
-	/* Look for cpu sysfs (x86 and others) */
-	scnprintf(path, PATH_MAX, "%s/bus/event_source/devices/cpu", sysfs);
-	if ((stat(path, &st) == 0) &&
-			(strncmp(name, "cpu", strlen("cpu")) == 0))
-		return 1;
-
 	/* Look for cpu sysfs (specific to arm) */
 	scnprintf(path, PATH_MAX, "%s/bus/event_source/devices/%s/cpus",
 				sysfs, name);
@@ -668,6 +663,7 @@ static void pmu_add_cpu_aliases(struct list_head *head, struct perf_pmu *pmu)
 	struct pmu_events_map *map;
 	struct pmu_event *pe;
 	const char *name = pmu->name;
+	const char *pname;
 
 	map = perf_pmu__find_map(pmu);
 	if (!map)
@@ -686,11 +682,9 @@ static void pmu_add_cpu_aliases(struct list_head *head, struct perf_pmu *pmu)
 			break;
 		}
 
-		if (!is_pmu_core(name)) {
-			/* check for uncore devices */
-			if (pe->pmu == NULL)
-				continue;
-			if (strncmp(pe->pmu, name, strlen(pe->pmu)))
+		if (!is_arm_pmu_core(name)) {
+			pname = pe->pmu ? pe->pmu : "cpu";
+			if (strncmp(pname, name, strlen(pname)))
 				continue;
 		}