Re: [patch 4/9] oom: Add missing rcu protection of __task_cred() in dump_tasks

KOSAKI Motohiro
2009-12-10T01:57:52Z

> dump_tasks accesses __task_cred() without being in a RCU read side
> critical section. tasklist_lock is not protecting that when
> CONFIG_TREE_PREEMPT_RCU=y.
>
> Add a rcu_read_lock/unlock() section around the code which accesses
> __task_cred().
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Cc: linux-mm@kvack.org
> ---
> mm/oom_kill.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> Index: linux-2.6-tip/mm/oom_kill.c
> ===================================================================
> --- linux-2.6-tip.orig/mm/oom_kill.c
> +++ linux-2.6-tip/mm/oom_kill.c
> @@ -329,10 +329,13 @@ static void dump_tasks(const struct mem_
> task_unlock(p);
> continue;
> }
> + /* Protect __task_cred() access */
> + rcu_read_lock();
> printk(KERN_INFO "[%5d] %5d %5d %8lu %8lu %3d %3d %s\n",
> p->pid, __task_cred(p)->uid, p->tgid, mm->total_vm,
> get_mm_rss(mm), (int)task_cpu(p), p->signal->oom_adj,
> p->comm);
> + rcu_read_unlock();
> task_unlock(p);
> } while_each_thread(g, p);
> }

Looks straight forward and correct to me.

Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>