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Subject[PATCH 22/30] perf tools: Use atomic_t to implement thread__{get,put} refcnt
Date
From: Arnaldo Carvalho de Melo <acme@redhat.com>

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>
---
tools/perf/util/thread.c | 6 +++---
tools/perf/util/thread.h | 3 ++-
2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
index 1c8fbc9..1b26552 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 9b8a54d..f33c48c 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 */
--
2.1.0


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