在 2022/4/12 22:31, Jason Gunthorpe 写道:
On Tue, Apr 12, 2022 at 10:28:16PM +0800, Yanjun Zhu wrote:
在 2022/4/12 21:53, Jason Gunthorpe 写道:
On Tue, Apr 12, 2022 at 09:43:28PM +0800, Yanjun Zhu wrote:
在 2022/4/11 19:50, Jason Gunthorpe 写道:
On Mon, Apr 11, 2022 at 04:00:18PM -0400, yanjun.zhu@xxxxxxxxx wrote:
@@ -138,8 +139,10 @@ 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_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);
No to using atomics, this needs to be either the _irq or _bh varient
If I understand you correctly, you mean that we should use
xa_lock_irq/xa_unlock_irq or xa_lock_bh/xa_unlock_bh instead of
xa_unlock_irqrestore?
This is correct
If so, xa_lock_irq/xa_unlock_irq or xa_lock_bh/xa_unlock_bh is used here,
the warning as below will appear. This means that __rxe_add_to_pool disables
softirq, but fpu_clone enables softirq.
I don't know what this is, you need to show the whole debug.
The followings are the warnings if xa_lock_bh + __xa_alloc(...,GFP_KERNEL)
is used. The diff is as below.
If xa_lock_irqsave/irqrestore + __xa_alloc(...,GFP_ATOMIC) is used,
the waring does not appear.
That is because this was called in an atomic context:
[ 92.107490] __rxe_add_to_pool+0x76/0xa0 [rdma_rxe]
[ 92.107500] rxe_create_ah+0x59/0xe0 [rdma_rxe]
[ 92.107511] _rdma_create_ah+0x148/0x180 [ib_core]
[ 92.107546] rdma_create_ah+0xb7/0xf0 [ib_core]
[ 92.107565] cm_alloc_msg+0x5c/0x170 [ib_cm]
[ 92.107577] cm_alloc_priv_msg+0x1b/0x50 [ib_cm]
[ 92.107584] ib_send_cm_req+0x213/0x3f0 [ib_cm]
[ 92.107613] rdma_connect_locked+0x238/0x8e0 [rdma_cm]
[ 92.107637] rdma_connect+0x2b/0x40 [rdma_cm]
[ 92.107646] ucma_connect+0x128/0x1a0 [rdma_ucm]
[ 92.107690] ucma_write+0xaf/0x140 [rdma_ucm]
[ 92.107698] vfs_write+0xb8/0x370
[ 92.107707] ksys_write+0xbb/0xd0
Meaning the GFP_KERNEL is already wrong.
The AH path needs to have its own special atomic allocation flow and
you have to use an irq lock and GFP_ATOMIC for it.
static struct ib_mad_send_buf *cm_alloc_msg(struct cm_id_private
*cm_id_priv)
{
...
spin_lock(&cm_id_priv->av.port->cm_dev->mad_agent_lock);
...
ah = rdma_create_ah(mad_agent->qp->pd, &cm_id_priv->av.ah_attr, 0);
...
spin_unlock(&cm_id_priv->av.port->cm_dev->mad_agent_lock);
...
}
Yes. Exactly.
In cm_alloc_msg, spinlock is used. And __rxe_add_to_pool should not use
GFP_KERNEL.
Thanks a lot. I will send the latest patch very soon.
Zhu Yanjun
Jason
