在 2024/7/11 9:01, Honggang LI 写道:
On Thu, Jul 11, 2024 at 11:06:06AM +0800, Greg Sword wrote:
Subject: Re: [PATCH] RDMA/rxe: Restore tasklet call for rxe_cq.c
From: Greg Sword <gregsword0@xxxxxxxxx>
Date: Thu, 11 Jul 2024 11:06:06 +0800
On Thu, Jul 11, 2024 at 9:41 AM Honggang LI <honggangli@xxxxxxx> wrote:
If ib_req_notify_cq() was called in complete handler, deadlock occurs
in receive path.
rxe_req_notify_cq+0x21/0x70 [rdma_rxe]
krping_cq_event_handler+0x26f/0x2c0 [rdma_krping]
What is rdma_krping? What is the deadlock?
https://github.com/larrystevenwise/krping.git
Please explain the deadlock in details.
88 int rxe_cq_post(struct rxe_cq *cq, struct rxe_cqe *cqe, int solicited)
89 {
90 struct ib_event ev;
91 int full;
92 void *addr;
93 unsigned long flags;
94
95 spin_lock_irqsave(&cq->cq_lock, flags); // Lock!
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
96
97 full = queue_full(cq->queue, QUEUE_TYPE_TO_CLIENT);
98 if (unlikely(full)) {
99 rxe_err_cq(cq, "queue full\n");
100 spin_unlock_irqrestore(&cq->cq_lock, flags);
101 if (cq->ibcq.event_handler) {
102 ev.device = cq->ibcq.device;
103 ev.element.cq = &cq->ibcq;
104 ev.event = IB_EVENT_CQ_ERR;
105 cq->ibcq.event_handler(&ev, cq->ibcq.cq_context);
106 }
107
108 return -EBUSY;
109 }
110
111 addr = queue_producer_addr(cq->queue, QUEUE_TYPE_TO_CLIENT);
112 memcpy(addr, cqe, sizeof(*cqe));
113
114 queue_advance_producer(cq->queue, QUEUE_TYPE_TO_CLIENT);
115
116 if ((cq->notify & IB_CQ_NEXT_COMP) ||
117 (cq->notify & IB_CQ_SOLICITED && solicited)) {
118 cq->notify = 0;
119 cq->ibcq.comp_handler(&cq->ibcq, cq->ibcq.cq_context);
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
call the complete handler krping_cq_event_handler()
120 }
121
122 spin_unlock_irqrestore(&cq->cq_lock, flags);
static void krping_cq_event_handler(struct ib_cq *cq, void *ctx)
{
struct krping_cb *cb = ctx;
struct ib_wc wc;
const struct ib_recv_wr *bad_wr;
int ret;
BUG_ON(cb->cq != cq);
if (cb->state == ERROR) {
printk(KERN_ERR PFX "cq completion in ERROR state\n");
return;
}
if (cb->frtest) {
printk(KERN_ERR PFX "cq completion event in frtest!\n");
return;
}
if (!cb->wlat && !cb->rlat && !cb->bw)
ib_req_notify_cq(cb->cq, IB_CQ_NEXT_COMP) > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
IMO, here, we can use a BH workqueue to execute this notification? Or
add an event handler?
Please reference other ULP kernel modules.
Thanks,
Zhu Yanjun
while ((ret = ib_poll_cq(cb->cq, 1, &wc)) == 1) {
if (wc.status) {
static int rxe_req_notify_cq(struct ib_cq *ibcq, enum ib_cq_notify_flags flags)
{
struct rxe_cq *cq = to_rcq(ibcq);
int ret = 0;
int empty;
unsigned long irq_flags;
spin_lock_irqsave(&cq->cq_lock, irq_flags);
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Deadlock
