On Wed, Apr 13, 2022 at 03:42:08AM -0400, 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
>
> 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
> </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>
> ---
> 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 | 17 ++++++++++++-----
> 1 file changed, 12 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/infiniband/sw/rxe/rxe_pool.c b/drivers/infiniband/sw/rxe/rxe_pool.c
> index 87066d04ed18..b9b147df4020 100644
> --- a/drivers/infiniband/sw/rxe/rxe_pool.c
> +++ b/drivers/infiniband/sw/rxe/rxe_pool.c
> @@ -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_bh(&pool->xa);
> + err = __xa_alloc_cyclic(&pool->xa, &elem->index, elem, pool->limit,
> + &pool->next, GFP_KERNEL);
> + xa_unlock_bh(&pool->xa);
> if (err)
> goto err_free;
You can't mix bh and not bh locks, either this is an irq spinlock or
it is bh spinlock, pick one and also ensure that the proper xa_init
flag is set.
> @@ -166,8 +168,10 @@ 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_irq(&pool->xa);
> + err = __xa_alloc_cyclic(&pool->xa, &elem->index, elem, pool->limit,
> + &pool->next, GFP_ATOMIC);
> + xa_unlock_irq(&pool->xa);
> if (err)
> goto err_cnt;
Still no, this does almost every allocation - only AH with the
non-blocking flag set should use this path.
Jason
