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@xxxxxxxxx wrote:
>>> From: Zhu Yanjun <yanjun.zhu@xxxxxxxxx>
>>>
>>> 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.
>
> 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@xxxxxxxxxx>
>>> Signed-off-by: Zhu Yanjun <yanjun.zhu@xxxxxxxxx>
>>> ---
>>> 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);
