linux-kernel - [tip:tracing/ftrace] tracing: Don't use tracing_record

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Message-ID: <tip-889a6c367283709a80dad9413488472596a1a1d2@git.kernel.org>
Date:	Fri, 13 Mar 2009 04:03:14 GMT
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	srostedt@...hat.com, tglx@...utronix.de,
	kosaki.motohiro@...fujitsu.com
Subject: [tip:tracing/ftrace] tracing: Don't use tracing_record_cmdline() in workqueue tracer fix

Commit-ID:  889a6c367283709a80dad9413488472596a1a1d2
Gitweb:     http://git.kernel.org/tip/889a6c367283709a80dad9413488472596a1a1d2
Author:     KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
AuthorDate: Fri, 13 Mar 2009 09:03:04 +0900
Commit:     Steven Rostedt <srostedt@...hat.com>
CommitDate: Thu, 12 Mar 2009 21:23:47 -0400

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@...fujitsu.com>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Signed-off-by: Steven Rostedt <srostedt@...hat.com>


---
 kernel/trace/trace_workqueue.c |   20 ++++++++++++++------
 1 files changed, 14 insertions(+), 6 deletions(-)

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 @@ static int workqueue_stat_show(struct seq_file *s, void *p)
 	struct cpu_workqueue_stats *cws = p;
 	unsigned long flags;
 	int cpu = cws->cpu;
-	struct task_struct *tsk = find_task_by_vpid(cws->pid);
-
-	seq_printf(s, "%3d %6d     %6u       %s\n", cws->cpu,
-		   atomic_read(&cws->inserted),
-		   cws->executed,
-		   tsk ? tsk->comm : "<...>");
+	struct pid *pid;
+	struct task_struct *tsk;
+
+	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)
--
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