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

[Bob Pearson <rpearsonhpe@gmail.com>]

On 4/15/22 02:42, Yanjun Zhu wrote:
> 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.

I have to go to bed. But the mr == NULL bug was fixed by the last 10 rxe pool patches.
I am sure it was the 8/10 patch which fixed it. I have never seen it once all the
rxe_pool patches were applied.

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