在 2022/4/13 22:50, Yanjun Zhu 写道:
在 2022/4/13 8:45, Jason Gunthorpe 写道:
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.
Got it. I should use irq spinlock. So XA_FLAGS_LOCK_IRQ is added in
xa_init flags.
So the code should be:
@@ -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_LOCK_IRQ | XA_FLAGS_ALLOC);
pool->limit.min = info->min_index;
pool->limit.max = info->max_index;
}
@@ -138,10 +138,10 @@ void *rxe_alloc(struct rxe_pool *pool)
elem->obj = obj;
kref_init(&elem->ref_cnt);
- xa_lock_bh(&pool->xa);
+ xa_lock_irq(&pool->xa);
err = __xa_alloc_cyclic(&pool->xa, &elem->index, elem,
pool->limit,
&pool->next, GFP_KERNEL);
- xa_unlock_bh(&pool->xa);
+ xa_unlock_irq(&pool->xa);
if (err)
goto err_free;
@@ -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.
Yes. Got it.
In the following, xa_lock_irqsave/xa_unlock_irqrestore should be used.
int ib_send_cm_req(struct ib_cm_id *cm_id,
struct ib_cm_req_param *param)
{
...
spin_lock_irqsave(&cm_id_priv->lock, flags);
...
__rxe_add_to_pool
...
spin_unlock_irqrestore(&cm_id_priv->lock, flags);
Hi，Jason
To the function ib_send_cm_req, the call chain is as below.
ib_send_cm_req --> cm_alloc_priv_msg --> cm_alloc_msg --> rdma_create_ah
--> _rdma_create_ah --> rxe_create_ah --> rxe_av_chk_attr
-->__rxe_add_to_pool
As such, xa_lock_irqsave/irqrestore is selected.
Zhu Yanjun
So the diff is as below:
@@ -157,6 +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;
@@ -168,10 +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);
- xa_lock_irq(&pool->xa);
+ xa_lock_irqsave(&pool->xa, flags);
err = __xa_alloc_cyclic(&pool->xa, &elem->index, elem,
pool->limit,
&pool->next, GFP_ATOMIC);
- xa_unlock_irq(&pool->xa);
+ xa_unlock_irqrestore(&pool->xa, flags);
if (err)
goto err_cnt;
Please comment. Thanks a lot.
Zhu Yanjun
Jason
