Re: [PATCHv4 1/2] RDMA/rxe: Fix a dead lock problem

[Yanjun Zhu <yanjun.zhu@linux.dev>]

在 2022/4/15 15:35, Bob Pearson 写道:
> On 4/15/22 02:32, Yanjun Zhu wrote:
>>
>> 在 2022/4/15 15:22, Bob Pearson 写道:
>>> On 4/15/22 01:49, Yanjun Zhu wrote:
>>>> 在 2022/4/15 14:35, Bob Pearson 写道:
>>>>> On 4/15/22 00:54, Yanjun Zhu wrote:
>>>>>> 在 2022/4/15 13:37, Bob Pearson 写道:
>>>>>>> On 4/15/22 14:56, yanjun.zhu@linux.dev wrote:
>>>>>>>> From: Zhu Yanjun <yanjun.zhu@linux.dev>
>>>>>>>>
>>>>>>>> This is a dead lock problem.
>>>>>>>> The xa_lock first is acquired in this:
>>>>>>>>
>>>>>>>> {SOFTIRQ-ON-W} state was registered at:
>>>>>>>>
>>>>>>>>       lock_acquire+0x1d2/0x5a0
>>>>>>>>       _raw_spin_lock+0x33/0x80
>>>>>>>>       __rxe_add_to_pool+0x183/0x230 [rdma_rxe]
>>>>>>>>       __ib_alloc_pd+0xf9/0x550 [ib_core]
>>>>>>>>       ib_mad_init_device+0x2d9/0xd20 [ib_core]
>>>>>>>>       add_client_context+0x2fa/0x450 [ib_core]
>>>>>>>>       enable_device_and_get+0x1b7/0x350 [ib_core]
>>>>>>>>       ib_register_device+0x757/0xaf0 [ib_core]
>>>>>>>>       rxe_register_device+0x2eb/0x390 [rdma_rxe]
>>>>>>>>       rxe_net_add+0x83/0xc0 [rdma_rxe]
>>>>>>>>       rxe_newlink+0x76/0x90 [rdma_rxe]
>>>>>>>>       nldev_newlink+0x245/0x3e0 [ib_core]
>>>>>>>>       rdma_nl_rcv_msg+0x2d4/0x790 [ib_core]
>>>>>>>>       rdma_nl_rcv+0x1ca/0x3f0 [ib_core]
>>>>>>>>       netlink_unicast+0x43b/0x640
>>>>>>>>       netlink_sendmsg+0x7eb/0xc40
>>>>>>>>       sock_sendmsg+0xe0/0x110
>>>>>>>>       __sys_sendto+0x1d7/0x2b0
>>>>>>>>       __x64_sys_sendto+0xdd/0x1b0
>>>>>>>>       do_syscall_64+0x37/0x80
>>>>>>>>       entry_SYSCALL_64_after_hwframe+0x44/0xae
>>>>>>> There is a separate xarray for each object pool. So this one is
>>>>>>> rxe->pd_pool.xa.xa_lock from rxe_alloc_pd().
>>>>>>>
>>>>>>>> Then xa_lock is acquired in this:
>>>>>>>>
>>>>>>>> {IN-SOFTIRQ-W}:
>>>>>>>>
>>>>>>>> Call Trace:
>>>>>>>>      <TASK>
>>>>>>>>       dump_stack_lvl+0x44/0x57
>>>>>>>>       mark_lock.part.52.cold.79+0x3c/0x46
>>>>>>>>       __lock_acquire+0x1565/0x34a0
>>>>>>>>       lock_acquire+0x1d2/0x5a0
>>>>>>>>       _raw_spin_lock_irqsave+0x42/0x90
>>>>>>>>       rxe_pool_get_index+0x72/0x1d0 [rdma_rxe]
>>>>>>>>       rxe_get_av+0x168/0x2a0 [rdma_rxe]
>>>>>>>>       rxe_requester+0x75b/0x4a90 [rdma_rxe]
>>>>>>>>       rxe_do_task+0x134/0x230 [rdma_rxe]
>>>>>>>>       tasklet_action_common.isra.12+0x1f7/0x2d0
>>>>>>>>       __do_softirq+0x1ea/0xa4c
>>>>>>>>       run_ksoftirqd+0x32/0x60
>>>>>>>>       smpboot_thread_fn+0x503/0x860
>>>>>>>>       kthread+0x29b/0x340
>>>>>>>>       ret_from_fork+0x1f/0x30
>>>>>>> And this one is rxe->ah_pool.xa.xa_lock from rxe_requester
>>>>>>> in the process of sending a UD packet from a work request
>>>>>>> which contains the index of the ah.
>>>>>>>
>>>>>>> For your story to work there needs to be an another ah_pool.xa.xa_lock somewhere.
>>>>>>> Let's assume it is there somewhere and it's from (a different) add_to_pool call
>>>>>>> then the add_to_pool_ routine should disable interrupts when it gets the lock
>>>>>>> with spin_lock_xxx. But only for AH objects.
>>>>>>>
>>>>>>> This may be old news.
>>>>>> What do you mean? Please check the call trace in the bug.
>>>>> I mean the trace you show here shows an instance of xa_lock being
>>>>> acquired from the pd pool followed by an instance of xa_lock being
>>>>> acquired from rxe_pool_get_index from the ah pool. They are different
>>>>> locks. They can't deadlock against each other. So there must be
>>>>> some other trace (not shown) that also gets xa_lock from the ah pool.
>>>> Please check the bug report mail. The link is news://nntp.lore.kernel.org:119/CAHj4cs-MT13RiEsWXUAcX_H5jEtjsebuZgSeUcfptNVuELgjYQ@mail.gmail.com
>>>>
>>>> BTW, what is the update about wr crash caused by your xarray patches?
>>>>
>>>> Zhu Yanjun
>>>>
>>>>>> Zhu Yanjun
>>>>>>
>>>>>>>>      </TASK>
>>>>>>>>
>>>>>>>>     From the above, in the function __rxe_add_to_pool,
>>>>>>>> xa_lock is acquired. Then the function __rxe_add_to_pool
>>>>>>>> is interrupted by softirq. The function
>>>>>>>> rxe_pool_get_index will also acquire xa_lock.
>>>>>>>>
>>>>>>>> Finally, the dead lock appears.
>>>>>>>>
>>>>>>>> [  296.806097]        CPU0
>>>>>>>> [  296.808550]        ----
>>>>>>>> [  296.811003]   lock(&xa->xa_lock#15);  <----- __rxe_add_to_pool
>>>>>>>> [  296.814583]   <Interrupt>
>>>>>>>> [  296.817209]     lock(&xa->xa_lock#15); <---- rxe_pool_get_index
>>>>>>>> [  296.820961]
>>>>>>>>                      *** DEADLOCK ***
>>>>>>>>
>>>>>>>> Fixes: 3225717f6dfa ("RDMA/rxe: Replace red-black trees by carrays")
>>>>>>>> Reported-and-tested-by: Yi Zhang <yi.zhang@redhat.com>
>>>>>>>> Signed-off-by: Zhu Yanjun <yanjun.zhu@linux.dev>
>>>>>>>> ---
>>>>>>>> V3->V4: xa_lock_irq locks are used.
>>>>>>>> V2->V3: __rxe_add_to_pool is between spin_lock and spin_unlock, so
>>>>>>>>             GFP_ATOMIC is used in __rxe_add_to_pool.
>>>>>>>> V1->V2: Replace GFP_KERNEL with GFP_ATOMIC
>>>>>>>> ---
>>>>>>>>      drivers/infiniband/sw/rxe/rxe_pool.c | 20 ++++++++++++++------
>>>>>>>>      1 file changed, 14 insertions(+), 6 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/drivers/infiniband/sw/rxe/rxe_pool.c b/drivers/infiniband/sw/rxe/rxe_pool.c
>>>>>>>> index 87066d04ed18..f1f06dc7e64f 100644
>>>>>>>> --- a/drivers/infiniband/sw/rxe/rxe_pool.c
>>>>>>>> +++ b/drivers/infiniband/sw/rxe/rxe_pool.c
>>>>>>>> @@ -106,7 +106,7 @@ void rxe_pool_init(struct rxe_dev *rxe, struct rxe_pool *pool,
>>>>>>>>            atomic_set(&pool->num_elem, 0);
>>>>>>>>      -    xa_init_flags(&pool->xa, XA_FLAGS_ALLOC);
>>>>>>>> +    xa_init_flags(&pool->xa, XA_FLAGS_ALLOC | XA_FLAGS_LOCK_IRQ);
>>>>>>>>          pool->limit.min = info->min_index;
>>>>>>>>          pool->limit.max = info->max_index;
>>>>>>>>      }
>>>>>>>> @@ -138,8 +138,10 @@ void *rxe_alloc(struct rxe_pool *pool)
>>>>>>>>          elem->obj = obj;
>>>>>>>>          kref_init(&elem->ref_cnt);
>>>>>>>>      -    err = xa_alloc_cyclic(&pool->xa, &elem->index, elem, pool->limit,
>>>>>>>> -                  &pool->next, GFP_KERNEL);
>>>>>>>> +    xa_lock_irq(&pool->xa);
>>>>>>>> +    err = __xa_alloc_cyclic(&pool->xa, &elem->index, elem, pool->limit,
>>>>>>>> +                &pool->next, GFP_KERNEL);
>>>>>>>> +    xa_unlock_irq(&pool->xa);
>>>>>>>>          if (err)
>>>>>>>>              goto err_free;
>>>>>>>>      @@ -155,6 +157,7 @@ void *rxe_alloc(struct rxe_pool *pool)
>>>>>>>>      int __rxe_add_to_pool(struct rxe_pool *pool, struct rxe_pool_elem *elem)
>>>>>>>>      {
>>>>>>>>          int err;
>>>>>>>> +    unsigned long flags;
>>>>>>>>            if (WARN_ON(pool->flags & RXE_POOL_ALLOC))
>>>>>>>>              return -EINVAL;
>>>>>>>> @@ -166,8 +169,10 @@ int __rxe_add_to_pool(struct rxe_pool *pool, struct rxe_pool_elem *elem)
>>>>>>>>          elem->obj = (u8 *)elem - pool->elem_offset;
>>>>>>>>          kref_init(&elem->ref_cnt);
>>>>>>>>      -    err = xa_alloc_cyclic(&pool->xa, &elem->index, elem, pool->limit,
>>>>>>>> -                  &pool->next, GFP_KERNEL);
>>>>>>>> +    xa_lock_irqsave(&pool->xa, flags);
>>>>>>>> +    err = __xa_alloc_cyclic(&pool->xa, &elem->index, elem, pool->limit,
>>>>>>>> +                &pool->next, GFP_ATOMIC);
>>>>>>>> +    xa_unlock_irqrestore(&pool->xa, flags);
>>>>>>>>          if (err)
>>>>>>>>              goto err_cnt;
>>>>>>>>      @@ -200,8 +205,11 @@ static void rxe_elem_release(struct kref *kref)
>>>>>>>>      {
>>>>>>>>          struct rxe_pool_elem *elem = container_of(kref, typeof(*elem), ref_cnt);
>>>>>>>>          struct rxe_pool *pool = elem->pool;
>>>>>>>> +    unsigned long flags;
>>>>>>>>      -    xa_erase(&pool->xa, elem->index);
>>>>>>>> +    xa_lock_irqsave(&pool->xa, flags);
>>>>>>>> +    __xa_erase(&pool->xa, elem->index);
>>>>>>>> +    xa_unlock_irqrestore(&pool->xa, flags);
>>>>>>>>            if (pool->cleanup)
>>>>>>>>              pool->cleanup(elem);
>>> Here is my output. Everything passes there are no bugs or unexpected warnings in the kernel trace.
>>
>> If I understand you correctly, you mean that the bug reported by Zhang Yi does not exist?
>>
>> I can reproduce this bug with rping.
>>
>> You can not reproduce this bug. It does not mean that this bug does not exist.
>>
>> And with rping, I also found another wr NULL bug. From the mail, you can also verify this wr NULL bug.
>>
>> Let us foucus on this wr NULL bug. OK?
>>
>> Zhu Yanjun
>>
>>>
>>> bob@ubuntu-21:~/src/blktests$ sudo ./check -q srp
>>>
>>> srp/001 (Create and remove LUNs)                             [passed]
>>>
>>>       runtime  3.402s  ...  2.753s
>>>
>>> srp/002 (File I/O on top of multipath concurrently with logout and login (mq)) [passed]time  34.431s  ...
>>>
>>>       runtime  34.431s  ...  34.328s
>>>
>>> srp/003 (File I/O on top of multipath concurrently with logout and login (sq)) [not run]
>>>
>>>       legacy device mapper support is missing
>>>
>>> srp/004 (File I/O on top of multipath concurrently with logout and login (sq-on-srp/004 (File I/O on top of multipath concurrently with logout and login (sq-on-mq)) [not run]
>>>
>>>       legacy device mapper support is missing
>>>
>>> srp/005 (Direct I/O with large transfer sizes, cmd_sg_entries=255 and bs=4M) [passed]
>>>
>>>       runtime  14.332s  ...  12.919s
>>>
>>> srp/006 (Direct I/O with large transfer sizes, cmd_sg_entries=255 and bs=8M) [passed]
>>>
>>>       runtime  13.361s  ...  12.959s
>>>
>>> srp/007 (Direct I/O with large transfer sizes, cmd_sg_entries=1 and bs=4M) [passed]
>>>
>>>       runtime  14.293s  ...  12.912s
>>>
>>> srp/008 (Direct I/O with large transfer sizes, cmd_sg_entries=1 and bs=8M) [passed]
>>>
>>>       runtime  13.369s  ...  13.165s
>>>
>>> srp/009 (Buffered I/O with large transfer sizes, cmd_sg_entries=255 and bs=4M) [passed]
>>>
>>>       runtime  13.636s  ...  14.201s
>>>
>>> srp/010 (Buffered I/O with large transfer sizes, cmd_sg_entries=255 and bs=8M) [passed]
>>>
>>>       runtime  13.361s  ...  12.909s
>>>
>>> srp/011 (Block I/O on top of multipath concurrently with logout and login) [passed]
>>>
>>>       runtime  33.706s  ...  33.571s
>>>
>>> srp/012 (dm-mpath on top of multiple I/O schedulers)         [passed]
>>>
>>>       runtime  13.592s  ...  14.138s
>>>
>>> srp/013 (Direct I/O using a discontiguous buffer)            [passed]
>>>
>>>       runtime  3.230s  ...  3.513s
>>>
>>> srp/014 (Run sg_reset while I/O is ongoing)                  [passed]
>>>
>>>       runtime  33.070s  ...  33.059s
>>>
>>> srp/015 (File I/O on top of multipath concurrently with logout and login (mq) using the SoftiWARP (siw) dsrp/015 (File I/O on top of multipath concurrently with logout and login (mq) using the SoftiWARP (siw) driver) [passed].148s  ...
>>
>> you are using SoftiWARP (siw)?
> 
> not me. it is just the normal behavior of the srp/015 test case. it has always done that. my rdma-core
> does support siw.

Fine.
Let us find the root cause of wr NULL problem.
I revert xarray patches and fell back to original source code.
This wr NULL problem does not exist.
I am working on it.

Hope we can fix this wr NULL problem very soon.

Zhu Yanjun

> 
>>
>>>
>>>       runtime  35.148s  ...  34.974s
>>>
>>> bob@ubuntu-21:~/src/blktests$
>>>
>>> Bob
>