perf thread: Fixes to thread__new() related to initializing comm

Freeing the thread on failure won't work with reference count checking,
use thread__delete().

Don't allocate the comm_str, use a stack allocation instead.

Fixes: f6005ca ("perf thread: Add reference count checking")
Signed-off-by: Ian Rogers <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: James Clark <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Kan Liang <[email protected]>
Cc: Leo Yan <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

Author: captain5050

tools/perf/util/thread.c

@@ -39,12 +39,13 @@ int thread__init_maps(struct thread *thread, struct machine *machine)
 
 struct thread *thread__new(pid_t pid, pid_t tid)
 {
-	char *comm_str;
-	struct comm *comm;
 	RC_STRUCT(thread) *_thread = zalloc(sizeof(*_thread));
 	struct thread *thread;
 
 	if (ADD_RC_CHK(thread, _thread) != NULL) {
+		struct comm *comm;
+		char comm_str[32];
+
 		thread__set_pid(thread, pid);
 		thread__set_tid(thread, tid);
 		thread__set_ppid(thread, -1);
@@ -56,13 +57,8 @@ struct thread *thread__new(pid_t pid, pid_t tid)
 		init_rwsem(thread__namespaces_lock(thread));
 		init_rwsem(thread__comm_lock(thread));
 
-		comm_str = malloc(32);
-		if (!comm_str)
-			goto err_thread;
-
-		snprintf(comm_str, 32, ":%d", tid);
+		snprintf(comm_str, sizeof(comm_str), ":%d", tid);
 		comm = comm__new(comm_str, 0, false);
-		free(comm_str);
 		if (!comm)
 			goto err_thread;
 
@@ -76,7 +72,7 @@ struct thread *thread__new(pid_t pid, pid_t tid)
 	return thread;
 
 err_thread:
-	free(thread);
+	thread__delete(thread);
 	return NULL;
 }