perf tools: Use atomic_t to implement thread__{get,put} refcnt

Fixing bugs in 'perf top' where the used thread unsafe 'struct thread'
refcount implementation was falling apart because we really use two
threads.

Acked-by: David Ahern <dsahern@gmail.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-hil2hol294u5ntcuof4jhmn6@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

2 files changed, 5 insertions, 4 deletions

diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
index 1c8fbc9588c5..1b265521836c 100644
--- a/tools/perf/util/thread.c
+++ b/tools/perf/util/thread.c
@@ -53,7 +53,7 @@ struct thread *thread__new(pid_t pid, pid_t tid)
                         goto err_thread;
 
                 list_add(&comm->list, &thread->comm_list);
-
+                atomic_set(&thread->refcnt, 0);
         }
 
         return thread;
@@ -84,13 +84,13 @@ void thread__delete(struct thread *thread)
 
 struct thread *thread__get(struct thread *thread)
 {
-        ++thread->refcnt;
+        atomic_inc(&thread->refcnt);
         return thread;
 }
 
 void thread__put(struct thread *thread)
 {
-        if (thread && --thread->refcnt == 0) {
+        if (thread && atomic_dec_and_test(&thread->refcnt)) {
                 list_del_init(&thread->node);
                 thread__delete(thread);
         }
diff --git a/tools/perf/util/thread.h b/tools/perf/util/thread.h
index 9b8a54dc34a8..f33c48cfdaa0 100644
--- a/tools/perf/util/thread.h
+++ b/tools/perf/util/thread.h
@@ -1,6 +1,7 @@
 #ifndef __PERF_THREAD_H
 #define __PERF_THREAD_H
 
+#include <linux/atomic.h>
 #include <linux/rbtree.h>
 #include <linux/list.h>
 #include <unistd.h>
@@ -21,7 +22,7 @@ struct thread {
         pid_t                   tid;
         pid_t                   ppid;
         int                     cpu;
-        int                     refcnt;
+        atomic_t                refcnt;
         char                    shortname[3];
         bool                    comm_set;
         bool                    dead; /* if set thread has exited */