2009-03-13 00:03:19

by KOSAKI Motohiro

Subject: [PATCH for tip] tracing: Don't use tracing_record_cmdline() in workqueue tracer fix

commit c3ffc7a40b7e94b094efe1c8ab4e24370a782b65 "Don't use tracing_record_cmdline()
in workqueue tracer" have a race window.

find_task_by_vpid() require task_list_lock(). but the patch doesn't.

fixing here.

Signed-off-by: KOSAKI Motohiro <[email protected]>
---
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)
--
1.6.0.6

2009-03-13 00:48:35

by Steven Rostedt

Subject: Re: [PATCH for tip] tracing: Don't use tracing_record_cmdline() in workqueue tracer fix

On Fri, 2009-03-13 at 09:03 +0900, KOSAKI Motohiro wrote:
> commit c3ffc7a40b7e94b094efe1c8ab4e24370a782b65 "Don't use tracing_record_cmdline()
> in workqueue tracer" have a race window.
>
> find_task_by_vpid() require task_list_lock(). but the patch doesn't.
>
> fixing here.
>
> Signed-off-by: KOSAKI Motohiro <[email protected]>
> ---

Applied, thanks!

-- Steve

2009-03-13 04:04:27

by KOSAKI Motohiro

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 <[email protected]>
AuthorDate: Fri, 13 Mar 2009 09:03:04 +0900
Commit: Steven Rostedt <[email protected]>
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: <[email protected]>
Signed-off-by: KOSAKI Motohiro <[email protected]>
Signed-off-by: Steven Rostedt <[email protected]>


---
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)