v4.19.13 snapshot.
diff --git a/tools/perf/util/comm.c b/tools/perf/util/comm.c
new file mode 100644
index 0000000..31279a7
--- /dev/null
+++ b/tools/perf/util/comm.c
@@ -0,0 +1,152 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "comm.h"
+#include "util.h"
+#include <errno.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <linux/refcount.h>
+#include "rwsem.h"
+
+struct comm_str {
+ char *str;
+ struct rb_node rb_node;
+ refcount_t refcnt;
+};
+
+/* Should perhaps be moved to struct machine */
+static struct rb_root comm_str_root;
+static struct rw_semaphore comm_str_lock = {.lock = PTHREAD_RWLOCK_INITIALIZER,};
+
+static struct comm_str *comm_str__get(struct comm_str *cs)
+{
+ if (cs && refcount_inc_not_zero(&cs->refcnt))
+ return cs;
+
+ return NULL;
+}
+
+static void comm_str__put(struct comm_str *cs)
+{
+ if (cs && refcount_dec_and_test(&cs->refcnt)) {
+ down_write(&comm_str_lock);
+ rb_erase(&cs->rb_node, &comm_str_root);
+ up_write(&comm_str_lock);
+ zfree(&cs->str);
+ free(cs);
+ }
+}
+
+static struct comm_str *comm_str__alloc(const char *str)
+{
+ struct comm_str *cs;
+
+ cs = zalloc(sizeof(*cs));
+ if (!cs)
+ return NULL;
+
+ cs->str = strdup(str);
+ if (!cs->str) {
+ free(cs);
+ return NULL;
+ }
+
+ refcount_set(&cs->refcnt, 1);
+
+ return cs;
+}
+
+static
+struct comm_str *__comm_str__findnew(const char *str, struct rb_root *root)
+{
+ struct rb_node **p = &root->rb_node;
+ struct rb_node *parent = NULL;
+ struct comm_str *iter, *new;
+ int cmp;
+
+ while (*p != NULL) {
+ parent = *p;
+ iter = rb_entry(parent, struct comm_str, rb_node);
+
+ /*
+ * If we race with comm_str__put, iter->refcnt is 0
+ * and it will be removed within comm_str__put call
+ * shortly, ignore it in this search.
+ */
+ cmp = strcmp(str, iter->str);
+ if (!cmp && comm_str__get(iter))
+ return iter;
+
+ if (cmp < 0)
+ p = &(*p)->rb_left;
+ else
+ p = &(*p)->rb_right;
+ }
+
+ new = comm_str__alloc(str);
+ if (!new)
+ return NULL;
+
+ rb_link_node(&new->rb_node, parent, p);
+ rb_insert_color(&new->rb_node, root);
+
+ return new;
+}
+
+static struct comm_str *comm_str__findnew(const char *str, struct rb_root *root)
+{
+ struct comm_str *cs;
+
+ down_write(&comm_str_lock);
+ cs = __comm_str__findnew(str, root);
+ up_write(&comm_str_lock);
+
+ return cs;
+}
+
+struct comm *comm__new(const char *str, u64 timestamp, bool exec)
+{
+ struct comm *comm = zalloc(sizeof(*comm));
+
+ if (!comm)
+ return NULL;
+
+ comm->start = timestamp;
+ comm->exec = exec;
+
+ comm->comm_str = comm_str__findnew(str, &comm_str_root);
+ if (!comm->comm_str) {
+ free(comm);
+ return NULL;
+ }
+
+ return comm;
+}
+
+int comm__override(struct comm *comm, const char *str, u64 timestamp, bool exec)
+{
+ struct comm_str *new, *old = comm->comm_str;
+
+ new = comm_str__findnew(str, &comm_str_root);
+ if (!new)
+ return -ENOMEM;
+
+ comm_str__put(old);
+ comm->comm_str = new;
+ comm->start = timestamp;
+ if (exec)
+ comm->exec = true;
+
+ return 0;
+}
+
+void comm__free(struct comm *comm)
+{
+ comm_str__put(comm->comm_str);
+ free(comm);
+}
+
+const char *comm__str(const struct comm *comm)
+{
+ return comm->comm_str->str;
+}