[PATCH 1/2] perf kvm: Support refcnt in structure kvm_info

Leo Yan
2023-03-20T06:16:43Z

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@linaro.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* become out-of-date due to an exec() or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