[RFC][PATCH] ps command race fix take2 [3/4] profile fix

[RFC][PATCH] ps command race fix take2 [3/4] profile fix

[KAMEZAWA Hiroyuki]

oprofile driver touches task->tasks.
But it doesn't have to use task->tasks, just list_head is needed.

Signed-Off-By: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

 drivers/oprofile/buffer_sync.c |    6 +++---
 include/linux/sched.h          |    4 ++++
 2 files changed, 7 insertions(+), 3 deletions(-)

Index: linux-2.6.18-rc4/include/linux/sched.h
===================================================================
--- linux-2.6.18-rc4.orig/include/linux/sched.h
+++ linux-2.6.18-rc4/include/linux/sched.h
@@ -808,6 +808,10 @@ struct task_struct {
 	struct list_head ptrace_children;
 	struct list_head ptrace_list;
 
+#if defined(CONFIG_OPROFILE) || defined(CONFIG_OPROFILE_MODULE)
+	struct list_head 	dead_tasks;
+#endif
+
 	struct mm_struct *mm, *active_mm;
 
 /* task state */
Index: linux-2.6.18-rc4/drivers/oprofile/buffer_sync.c
===================================================================
--- linux-2.6.18-rc4.orig/drivers/oprofile/buffer_sync.c
+++ linux-2.6.18-rc4/drivers/oprofile/buffer_sync.c
@@ -51,7 +51,7 @@ static int task_free_notify(struct notif
 	unsigned long flags;
 	struct task_struct * task = data;
 	spin_lock_irqsave(&task_mortuary, flags);
-	list_add(&task->tasks, &dying_tasks);
+	list_add(&task->dead_tasks, &dying_tasks);
 	spin_unlock_irqrestore(&task_mortuary, flags);
 	return NOTIFY_OK;
 }
@@ -446,8 +446,8 @@ static void process_task_mortuary(void)
 
 	spin_unlock_irqrestore(&task_mortuary, flags);
 
-	list_for_each_entry_safe(task, ttask, &local_dead_tasks, tasks) {
-		list_del(&task->tasks);
+	list_for_each_entry_safe(task, ttask, &local_dead_tasks, dead_tasks) {
+		list_del(&task->dead_tasks);
 		free_task(task);
 	}
 }

Re: [RFC][PATCH] ps command race fix take2 [3/4] profile fix

[Andi Kleen]

KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> writes:

> ===================================================================
> --- linux-2.6.18-rc4.orig/include/linux/sched.h
> +++ linux-2.6.18-rc4/include/linux/sched.h
> @@ -808,6 +808,10 @@ struct task_struct {
>  	struct list_head ptrace_children;
>  	struct list_head ptrace_list;
>  
> +#if defined(CONFIG_OPROFILE) || defined(CONFIG_OPROFILE_MODULE)
> +	struct list_head 	dead_tasks;
> +#endif

Sorry I think this needs a cleaner solution without ifdef.   Why can't it use
the token list? Or some other list head that's unused then.

Otherwise I would think it it better to use a separate list object to
maintain this list in oprofile.

-Andi

Re: [RFC][PATCH] ps command race fix take2 [3/4] profile fix

[KAMEZAWA Hiroyuki]

On 22 Aug 2006 13:08:49 +0200
Andi Kleen <ak@suse.de> wrote:

> KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> writes:
> 
> > ===================================================================
> > --- linux-2.6.18-rc4.orig/include/linux/sched.h
> > +++ linux-2.6.18-rc4/include/linux/sched.h
> > @@ -808,6 +808,10 @@ struct task_struct {
> >  	struct list_head ptrace_children;
> >  	struct list_head ptrace_list;
> >  
> > +#if defined(CONFIG_OPROFILE) || defined(CONFIG_OPROFILE_MODULE)
> > +	struct list_head 	dead_tasks;
> > +#endif
> 
> Sorry I think this needs a cleaner solution without ifdef.   Why can't it use
> the token list? Or some other list head that's unused then.
> 

I added them because oprofile doesn't need tokened-list. But adding new
member only for this seems a bit expensive as you point out.
I'll find another way, reuse some list_head or use tokened-list.

-Kame