linux-kernel - Re: [PATCH] nvmet,rxe: defer ip datagram sending to tasklet

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Date:   Mon, 7 May 2018 16:48:56 +0800
From:   Yanjun Zhu <yanjun.zhu@...cle.com>
To:     Alexandru Moise <00moses.alexander00@...il.com>,
        monis@...lanox.com, dledford@...hat.com, jgg@...pe.ca,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nvmet,rxe: defer ip datagram sending to tasklet


On 2018/5/7 6:20, Alexandru Moise wrote:
> When using NVME over Fabrics we may end up sending IP
> packets in interrupt context, we should defer this work
> to a tasklet.
>
> [   50.939957] WARNING: CPU: 3 PID: 0 at kernel/softirq.c:161 __local_bh_enable_ip+0x1f/0xa0
> [   50.942602] CPU: 3 PID: 0 Comm: swapper/3 Kdump: loaded Tainted: G        W         4.17.0-rc3-ARCH+ #104
> [   50.945466] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-20171110_100015-anatol 04/01/2014
> [   50.948163] RIP: 0010:__local_bh_enable_ip+0x1f/0xa0
> [   50.949631] RSP: 0018:ffff88009c183900 EFLAGS: 00010006
> [   50.951029] RAX: 0000000080010403 RBX: 0000000000000200 RCX: 0000000000000001
> [   50.952636] RDX: 0000000000000000 RSI: 0000000000000200 RDI: ffffffff817e04ec
> [   50.954278] RBP: ffff88009c183910 R08: 0000000000000001 R09: 0000000000000614
> [   50.956000] R10: ffffea00021d5500 R11: 0000000000000001 R12: ffffffff817e04ec
> [   50.957779] R13: 0000000000000000 R14: ffff88009566f400 R15: ffff8800956c7000
> [   50.959402] FS:  0000000000000000(0000) GS:ffff88009c180000(0000) knlGS:0000000000000000
> [   50.961552] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   50.963798] CR2: 000055c4ec0ccac0 CR3: 0000000002209001 CR4: 00000000000606e0
> [   50.966121] Call Trace:
> [   50.966845]  <IRQ>
> [   50.967497]  __dev_queue_xmit+0x62d/0x690
> [   50.968722]  dev_queue_xmit+0x10/0x20
> [   50.969894]  neigh_resolve_output+0x173/0x190
> [   50.971244]  ip_finish_output2+0x2b8/0x370
> [   50.972527]  ip_finish_output+0x1d2/0x220
> [   50.973785]  ? ip_finish_output+0x1d2/0x220
> [   50.975010]  ip_output+0xd4/0x100
> [   50.975903]  ip_local_out+0x3b/0x50
> [   50.976823]  rxe_send+0x74/0x120
> [   50.977702]  rxe_requester+0xe3b/0x10b0
> [   50.978881]  ? ip_local_deliver_finish+0xd1/0xe0
> [   50.980260]  rxe_do_task+0x85/0x100
> [   50.981386]  rxe_run_task+0x2f/0x40
> [   50.982470]  rxe_post_send+0x51a/0x550
> [   50.983591]  nvmet_rdma_queue_response+0x10a/0x170
> [   50.985024]  __nvmet_req_complete+0x95/0xa0
> [   50.986287]  nvmet_req_complete+0x15/0x60
> [   50.987469]  nvmet_bio_done+0x2d/0x40
> [   50.988564]  bio_endio+0x12c/0x140
> [   50.989654]  blk_update_request+0x185/0x2a0
> [   50.990947]  blk_mq_end_request+0x1e/0x80
> [   50.991997]  nvme_complete_rq+0x1cc/0x1e0
> [   50.993171]  nvme_pci_complete_rq+0x117/0x120
> [   50.994355]  __blk_mq_complete_request+0x15e/0x180
> [   50.995988]  blk_mq_complete_request+0x6f/0xa0
> [   50.997304]  nvme_process_cq+0xe0/0x1b0
> [   50.998494]  nvme_irq+0x28/0x50
> [   50.999572]  __handle_irq_event_percpu+0xa2/0x1c0
> [   51.000986]  handle_irq_event_percpu+0x32/0x80
> [   51.002356]  handle_irq_event+0x3c/0x60
> [   51.003463]  handle_edge_irq+0x1c9/0x200
> [   51.004473]  handle_irq+0x23/0x30
> [   51.005363]  do_IRQ+0x46/0xd0
> [   51.006182]  common_interrupt+0xf/0xf
> [   51.007129]  </IRQ>
>
> Signed-off-by: Alexandru Moise <00moses.alexander00@...il.com>
> ---
>   drivers/infiniband/sw/rxe/rxe_verbs.c | 14 +++++++++++++-
>   1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/infiniband/sw/rxe/rxe_verbs.c b/drivers/infiniband/sw/rxe/rxe_verbs.c
> index 2cb52fd48cf1..b84881077f8b 100644
> --- a/drivers/infiniband/sw/rxe/rxe_verbs.c
> +++ b/drivers/infiniband/sw/rxe/rxe_verbs.c
> @@ -798,6 +798,9 @@ static int rxe_post_send_kernel(struct rxe_qp *qp, struct ib_send_wr *wr,
>   	must_sched = (qp_type(qp) == IB_QPT_GSI) ||
>   			(queue_count(qp->sq.queue) > 1);
>   
> +	if (in_irq())
> +		must_sched = 1;
Can we use the following to replace this block?

must_sched = (qp_type(qp) == IB_QPT_GSI) ||
              (queue_count(qp->sq.queue) > 1) || in_irq();

Zhu Yanjun
> +
>   	rxe_run_task(&qp->req.task, must_sched);
>   	if (unlikely(qp->req.state == QP_STATE_ERROR))
>   		rxe_run_task(&qp->comp.task, 1);
> @@ -809,6 +812,7 @@ static int rxe_post_send(struct ib_qp *ibqp, struct ib_send_wr *wr,
>   			 struct ib_send_wr **bad_wr)
>   {
>   	struct rxe_qp *qp = to_rqp(ibqp);
> +	int must_sched = 0;
>   
>   	if (unlikely(!qp->valid)) {
>   		*bad_wr = wr;
> @@ -821,8 +825,16 @@ static int rxe_post_send(struct ib_qp *ibqp, struct ib_send_wr *wr,
>   	}
>   
>   	if (qp->is_user) {
> +		/*
> +		 * NVME over fabrics can enter this path in
> +		 * interrupt context, offload datagram
> +		 * sending to rxe tasklet.
> +		 */
> +		if (in_irq())
> +			must_sched = 1;
> +
>   		/* Utilize process context to do protocol processing */
> -		rxe_run_task(&qp->req.task, 0);
> +		rxe_run_task(&qp->req.task, must_sched);
>   		return 0;
>   	} else
>   		return rxe_post_send_kernel(qp, wr, bad_wr);