tracing: Don't use tracing_record_cmdline() in workqueue tracer fix
commit c3ffc7a40b7e94b094efe1c8ab4e24370a782b65
"Don't use tracing_record_cmdline() in workqueue tracer"
has a race window.
find_task_by_vpid() requires task_list_lock().
LKML-Reference: <20090313090042.43CD.A69D9226@jp.fujitsu.com>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
diff --git a/kernel/trace/trace_workqueue.c b/kernel/trace/trace_workqueue.c
index fb5ccac..9ab035b 100644
--- a/kernel/trace/trace_workqueue.c
+++ b/kernel/trace/trace_workqueue.c
@@ -193,12 +193,20 @@
struct cpu_workqueue_stats *cws = p;
unsigned long flags;
int cpu = cws->cpu;
- struct task_struct *tsk = find_task_by_vpid(cws->pid);
+ struct pid *pid;
+ struct task_struct *tsk;
- seq_printf(s, "%3d %6d %6u %s\n", cws->cpu,
- atomic_read(&cws->inserted),
- cws->executed,
- tsk ? tsk->comm : "<...>");
+ pid = find_get_pid(cws->pid);
+ if (pid) {
+ tsk = get_pid_task(pid, PIDTYPE_PID);
+ if (tsk) {
+ seq_printf(s, "%3d %6d %6u %s\n", cws->cpu,
+ atomic_read(&cws->inserted), cws->executed,
+ tsk->comm);
+ put_task_struct(tsk);
+ }
+ put_pid(pid);
+ }
spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
if (&cws->list == workqueue_cpu_stat(cpu)->list.next)
