On Fri, 10 Jun 2011 13:21:46 +0800 Xiaotian Feng <xtfeng@xxxxxxxxx> wrote: > On Fri, Jun 10, 2011 at 12:30 PM, KAMEZAWA Hiroyuki < > kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > > > > > I think this can be a fix. > > maybe good to CC Oleg. > > == > > From dff52fb35af0cf36486965d19ee79e04b59f1dc4 Mon Sep 17 00:00:00 2001 > > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > > Date: Fri, 10 Jun 2011 13:15:14 +0900 > > Subject: [PATCH] [BUGFIX] update mm->owner even if no next owner. > > > > A panic is reported. > > > > > Call Trace: > > > [<ffffffff81139792>] mem_cgroup_from_task+0x15/0x17 > > > [<ffffffff8113a75a>] __mem_cgroup_try_charge+0x148/0x4b4 > > > [<ffffffff810493f3>] ? need_resched+0x23/0x2d > > > [<ffffffff814cbf43>] ? preempt_schedule+0x46/0x4f > > > [<ffffffff8113afe8>] mem_cgroup_charge_common+0x9a/0xce > > > [<ffffffff8113b6d1>] mem_cgroup_newpage_charge+0x5d/0x5f > > > [<ffffffff81134024>] khugepaged+0x5da/0xfaf > > > [<ffffffff81078ea0>] ? __init_waitqueue_head+0x4b/0x4b > > > [<ffffffff81133a4a>] ? add_mm_counter.constprop.5+0x13/0x13 > > > [<ffffffff81078625>] kthread+0xa8/0xb0 > > > [<ffffffff814d13e8>] ? sub_preempt_count+0xa1/0xb4 > > > [<ffffffff814d5664>] kernel_thread_helper+0x4/0x10 > > > [<ffffffff814ce858>] ? retint_restore_args+0x13/0x13 > > > [<ffffffff8107857d>] ? __init_kthread_worker+0x5a/0x5a > > > > The code is. > > > return container_of(task_subsys_state(p, mem_cgroup_subsys_id), > > > struct mem_cgroup, css); > > > > > > What happens here is accssing a freed task struct "p" from mm->owner. > > So, it's doubtful that mm->owner points to freed task struct. > > > > > But from the bug itself, it looks more likely kernel is hitting a freed > p->cgroups, right? > If p is already freed, the kernel will fault on > 781cc62d: 8b 82 fc 08 00 00 mov 0x8fc(%edx),%eax > > Then you will not get a value of 6b6b6b87, right? %edx here is a pointer for task struct. Then, task->cgroup == 0x6b6b6b6b. It means "task" is freed. Thanks, -Kame -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>