linux-kernel - [PATCH 1/2] perf kvm: Support refcnt in structure kvm

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Message-Id: <20230320061619.29520-2-leo.yan@linaro.org>
Date:   Mon, 20 Mar 2023 14:16:18 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        James Clark <james.clark@....com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Leo Yan <leo.yan@...aro.org>
Subject: [PATCH 1/2] perf kvm: Support refcnt in structure kvm_info

hists__add_entry_ops() doesn't allocate a new histograms entry if it has
an existed entry for a KVM event, in this case, find_create_kvm_event()
allocates structure kvm_info but it's not used by any histograms and
never freed.

To fix the memory leak, this patch firstly introduces refcnt and a set
of functions for refcnt operations in the structure kvm_info.  When the
data structure is not used anymore, it invokes kvm_info__zput() to
decrease reference count and release the structure.

Signed-off-by: Leo Yan <leo.yan@...aro.org>
---
 tools/perf/builtin-kvm.c   |  3 +--
 tools/perf/util/hist.c     |  5 +++++
 tools/perf/util/kvm-stat.h | 37 +++++++++++++++++++++++++++++++++++++
 3 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/tools/perf/builtin-kvm.c b/tools/perf/builtin-kvm.c
index 4c205df5106f..1e1cb5a9d0a2 100644
--- a/tools/perf/builtin-kvm.c
+++ b/tools/perf/builtin-kvm.c
@@ -768,7 +768,6 @@ static void kvm_he_free(void *he)
 {
 	struct kvm_event *kvm_ev;
 
-	free(((struct hist_entry *)he)->kvm_info);
 	kvm_ev = container_of(he, struct kvm_event, he);
 	free(kvm_ev);
 }
@@ -788,7 +787,7 @@ static struct kvm_event *find_create_kvm_event(struct perf_kvm_stat *kvm,
 
 	BUG_ON(key->key == INVALID_KEY);
 
-	ki = zalloc(sizeof(*ki));
+	ki = kvm_info__new();
 	if (!ki) {
 		pr_err("Failed to allocate kvm info\n");
 		return NULL;
diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c
index 3670136a0074..b296f572f881 100644
--- a/tools/perf/util/hist.c
+++ b/tools/perf/util/hist.c
@@ -628,6 +628,8 @@ static struct hist_entry *hists__findnew_entry(struct hists *hists,
 
 			block_info__zput(entry->block_info);
 
+			kvm_info__zput(entry->kvm_info);
+
 			/* If the map of an existing hist_entry has
 			 * become out-of-date due to an exec() or
 			 * similar, update it.  Otherwise we will
@@ -1323,6 +1325,9 @@ void hist_entry__delete(struct hist_entry *he)
 	if (he->block_info)
 		block_info__zput(he->block_info);
 
+	if (he->kvm_info)
+		kvm_info__zput(he->kvm_info);
+
 	zfree(&he->res_samples);
 	zfree(&he->stat_acc);
 	free_srcline(he->srcline);
diff --git a/tools/perf/util/kvm-stat.h b/tools/perf/util/kvm-stat.h
index bc6c8e38ef50..9bf34c0e0056 100644
--- a/tools/perf/util/kvm-stat.h
+++ b/tools/perf/util/kvm-stat.h
@@ -10,6 +10,9 @@
 #include "symbol.h"
 #include "record.h"
 
+#include <stdlib.h>
+#include <linux/zalloc.h>
+
 #define KVM_EVENT_NAME_LEN	40
 
 struct evsel;
@@ -25,6 +28,7 @@ struct event_key {
 
 struct kvm_info {
 	char name[KVM_EVENT_NAME_LEN];
+	refcount_t refcnt;
 };
 
 struct kvm_event_stats {
@@ -145,6 +149,39 @@ extern const char *vcpu_id_str;
 extern const char *kvm_exit_reason;
 extern const char *kvm_entry_trace;
 extern const char *kvm_exit_trace;
+
+static inline struct kvm_info *kvm_info__get(struct kvm_info *ki)
+{
+	if (ki)
+		refcount_inc(&ki->refcnt);
+	return ki;
+}
+
+static inline void kvm_info__put(struct kvm_info *ki)
+{
+	if (ki && refcount_dec_and_test(&ki->refcnt))
+		free(ki);
+}
+
+static inline void __kvm_info__zput(struct kvm_info **ki)
+{
+	kvm_info__put(*ki);
+	*ki = NULL;
+}
+
+#define kvm_info__zput(ki) __kvm_info__zput(&ki)
+
+static inline struct kvm_info *kvm_info__new(void)
+{
+	struct kvm_info *ki;
+
+	ki = zalloc(sizeof(*ki));
+	if (ki)
+		refcount_set(&ki->refcnt, 1);
+
+	return ki;
+}
+
 #endif /* HAVE_KVM_STAT_SUPPORT */
 
 extern int kvm_add_default_arch_event(int *argc, const char **argv);
-- 
2.39.2