On 11/08/2012 01:51 AM, Glauber Costa wrote:
> On 11/07/2012 04:53 PM, Sasha Levin wrote:
>> On 11/01/2012 08:07 AM, Glauber Costa wrote:
>>> SLUB allows us to tune a particular cache behavior with sysfs-based
>>> tunables. When creating a new memcg cache copy, we'd like to preserve
>>> any tunables the parent cache already had.
>>>
>>> This can be done by tapping into the store attribute function provided
>>> by the allocator. We of course don't need to mess with read-only
>>> fields. Since the attributes can have multiple types and are stored
>>> internally by sysfs, the best strategy is to issue a ->show() in the
>>> root cache, and then ->store() in the memcg cache.
>>>
>>> The drawback of that, is that sysfs can allocate up to a page in
>>> buffering for show(), that we are likely not to need, but also can't
>>> guarantee. To avoid always allocating a page for that, we can update the
>>> caches at store time with the maximum attribute size ever stored to the
>>> root cache. We will then get a buffer big enough to hold it. The
>>> corolary to this, is that if no stores happened, nothing will be
>>> propagated.
>>>
>>> It can also happen that a root cache has its tunables updated during
>>> normal system operation. In this case, we will propagate the change to
>>> all caches that are already active.
>>>
>>> Signed-off-by: Glauber Costa <glommer@xxxxxxxxxxxxx>
>>> CC: Christoph Lameter <cl@xxxxxxxxx>
>>> CC: Pekka Enberg <penberg@xxxxxxxxxxxxxx>
>>> CC: Michal Hocko <mhocko@xxxxxxx>
>>> CC: Kamezawa Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
>>> CC: Johannes Weiner <hannes@xxxxxxxxxxx>
>>> CC: Suleiman Souhlal <suleiman@xxxxxxxxxx>
>>> CC: Tejun Heo <tj@xxxxxxxxxx>
>>> ---
>>
>> Hi guys,
>>
>> This patch is making lockdep angry! *bark bark*
>>
>> [ 351.935003] ======================================================
>> [ 351.937693] [ INFO: possible circular locking dependency detected ]
>> [ 351.939720] 3.7.0-rc4-next-20121106-sasha-00008-g353b62f #117 Tainted: G W
>> [ 351.942444] -------------------------------------------------------
>> [ 351.943528] trinity-child13/6961 is trying to acquire lock:
>> [ 351.943528] (s_active#43){++++.+}, at: [<ffffffff812f9e11>] sysfs_addrm_finish+0x31/0x60
>> [ 351.943528]
>> [ 351.943528] but task is already holding lock:
>> [ 351.943528] (slab_mutex){+.+.+.}, at: [<ffffffff81228a42>] kmem_cache_destroy+0x22/0xe0
>> [ 351.943528]
>> [ 351.943528] which lock already depends on the new lock.
>> [ 351.943528]
>> [ 351.943528]
>> [ 351.943528] the existing dependency chain (in reverse order) is:
>> [ 351.943528]
>> -> #1 (slab_mutex){+.+.+.}:
>> [ 351.960334] [<ffffffff8118536a>] lock_acquire+0x1aa/0x240
>> [ 351.960334] [<ffffffff83a944d9>] __mutex_lock_common+0x59/0x5a0
>> [ 351.960334] [<ffffffff83a94a5f>] mutex_lock_nested+0x3f/0x50
>> [ 351.960334] [<ffffffff81256a6e>] slab_attr_store+0xde/0x110
>> [ 351.960334] [<ffffffff812f820a>] sysfs_write_file+0xfa/0x150
>> [ 351.960334] [<ffffffff8127a220>] vfs_write+0xb0/0x180
>> [ 351.960334] [<ffffffff8127a540>] sys_pwrite64+0x60/0xb0
>> [ 351.960334] [<ffffffff83a99298>] tracesys+0xe1/0xe6
>> [ 351.960334]
>> -> #0 (s_active#43){++++.+}:
>> [ 351.960334] [<ffffffff811825af>] __lock_acquire+0x14df/0x1ca0
>> [ 351.960334] [<ffffffff8118536a>] lock_acquire+0x1aa/0x240
>> [ 351.960334] [<ffffffff812f9272>] sysfs_deactivate+0x122/0x1a0
>> [ 351.960334] [<ffffffff812f9e11>] sysfs_addrm_finish+0x31/0x60
>> [ 351.960334] [<ffffffff812fa369>] sysfs_remove_dir+0x89/0xd0
>> [ 351.960334] [<ffffffff819e1d96>] kobject_del+0x16/0x40
>> [ 351.960334] [<ffffffff8125ed40>] __kmem_cache_shutdown+0x40/0x60
>> [ 351.960334] [<ffffffff81228a60>] kmem_cache_destroy+0x40/0xe0
>> [ 351.960334] [<ffffffff82b21058>] mon_text_release+0x78/0xe0
>> [ 351.960334] [<ffffffff8127b3b2>] __fput+0x122/0x2d0
>> [ 351.960334] [<ffffffff8127b569>] ____fput+0x9/0x10
>> [ 351.960334] [<ffffffff81131b4e>] task_work_run+0xbe/0x100
>> [ 351.960334] [<ffffffff81110742>] do_exit+0x432/0xbd0
>> [ 351.960334] [<ffffffff81110fa4>] do_group_exit+0x84/0xd0
>> [ 351.960334] [<ffffffff8112431d>] get_signal_to_deliver+0x81d/0x930
>> [ 351.960334] [<ffffffff8106d5aa>] do_signal+0x3a/0x950
>> [ 351.960334] [<ffffffff8106df1e>] do_notify_resume+0x3e/0x90
>> [ 351.960334] [<ffffffff83a993aa>] int_signal+0x12/0x17
>> [ 351.960334]
>> [ 351.960334] other info that might help us debug this:
>> [ 351.960334]
>> [ 351.960334] Possible unsafe locking scenario:
>> [ 351.960334]
>> [ 351.960334] CPU0 CPU1
>> [ 351.960334] ---- ----
>> [ 351.960334] lock(slab_mutex);
>> [ 351.960334] lock(s_active#43);
>> [ 351.960334] lock(slab_mutex);
>> [ 351.960334] lock(s_active#43);
>> [ 351.960334]
>> [ 351.960334] *** DEADLOCK ***
>> [ 351.960334]
>> [ 351.960334] 2 locks held by trinity-child13/6961:
>> [ 351.960334] #0: (mon_lock){+.+.+.}, at: [<ffffffff82b21005>] mon_text_release+0x25/0xe0
>> [ 351.960334] #1: (slab_mutex){+.+.+.}, at: [<ffffffff81228a42>] kmem_cache_destroy+0x22/0xe0
>> [ 351.960334]
>> [ 351.960334] stack backtrace:
>> [ 351.960334] Pid: 6961, comm: trinity-child13 Tainted: G W 3.7.0-rc4-next-20121106-sasha-00008-g353b62f #117
>> [ 351.960334] Call Trace:
>> [ 351.960334] [<ffffffff83a3c736>] print_circular_bug+0x1fb/0x20c
>> [ 351.960334] [<ffffffff811825af>] __lock_acquire+0x14df/0x1ca0
>> [ 351.960334] [<ffffffff81184045>] ? debug_check_no_locks_freed+0x185/0x1e0
>> [ 351.960334] [<ffffffff8118536a>] lock_acquire+0x1aa/0x240
>> [ 351.960334] [<ffffffff812f9e11>] ? sysfs_addrm_finish+0x31/0x60
>> [ 351.960334] [<ffffffff812f9272>] sysfs_deactivate+0x122/0x1a0
>> [ 351.960334] [<ffffffff812f9e11>] ? sysfs_addrm_finish+0x31/0x60
>> [ 351.960334] [<ffffffff812f9e11>] sysfs_addrm_finish+0x31/0x60
>> [ 351.960334] [<ffffffff812fa369>] sysfs_remove_dir+0x89/0xd0
>> [ 351.960334] [<ffffffff819e1d96>] kobject_del+0x16/0x40
>> [ 351.960334] [<ffffffff8125ed40>] __kmem_cache_shutdown+0x40/0x60
>> [ 351.960334] [<ffffffff81228a60>] kmem_cache_destroy+0x40/0xe0
>> [ 351.960334] [<ffffffff82b21058>] mon_text_release+0x78/0xe0
>> [ 351.960334] [<ffffffff8127b3b2>] __fput+0x122/0x2d0
>> [ 351.960334] [<ffffffff8127b569>] ____fput+0x9/0x10
>> [ 351.960334] [<ffffffff81131b4e>] task_work_run+0xbe/0x100
>> [ 351.960334] [<ffffffff81110742>] do_exit+0x432/0xbd0
>> [ 351.960334] [<ffffffff811243b9>] ? get_signal_to_deliver+0x8b9/0x930
>> [ 351.960334] [<ffffffff8117d402>] ? get_lock_stats+0x22/0x70
>> [ 351.960334] [<ffffffff8117d48e>] ? put_lock_stats.isra.16+0xe/0x40
>> [ 351.960334] [<ffffffff83a977fb>] ? _raw_spin_unlock_irq+0x2b/0x80
>> [ 351.960334] [<ffffffff81110fa4>] do_group_exit+0x84/0xd0
>> [ 351.960334] [<ffffffff8112431d>] get_signal_to_deliver+0x81d/0x930
>> [ 351.960334] [<ffffffff8117d48e>] ? put_lock_stats.isra.16+0xe/0x40
>> [ 351.960334] [<ffffffff8106d5aa>] do_signal+0x3a/0x950
>> [ 351.960334] [<ffffffff811c8b33>] ? rcu_cleanup_after_idle+0x23/0x170
>> [ 351.960334] [<ffffffff811cc1c4>] ? rcu_eqs_exit_common+0x64/0x3a0
>> [ 351.960334] [<ffffffff811caa5d>] ? rcu_user_enter+0x10d/0x140
>> [ 351.960334] [<ffffffff811cc8d5>] ? rcu_user_exit+0xc5/0xf0
>> [ 351.960334] [<ffffffff8106df1e>] do_notify_resume+0x3e/0x90
>> [ 351.960334] [<ffffffff83a993aa>] int_signal+0x12/0x17
>>
>>
>> Thanks,
>> Sasha
>
> Hello Sasha,
>
> May I ask how did you trigger this ?
Fuzzing with trinity, inside a KVM guest.
Thanks,
Sasha
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