prov/verbs: account for off-by-one credit initialization

[ooststep]

When we are enabling flow control, we artificially inject
a credit so that the credit messaging itself is not blocked
by a lack of credits. To counter this, we will adjust the number
of credits we send the first time by initializing to -1.

[shefty]

Intel CI is reporting a failure, but looking at the details, everything shows passing. Maybe it was restarted? Anyway, changes look good. Thanks

[swelch]

@shefty, @ooststep - Looks like the commit associated with this PR breaks ofi_rxm;verbs with FI_OFI_RXM_USE_SRX=1 when running osu_bw benchmark.

`Program terminated with signal SIGSEGV, Segmentation fault.
#0 0x00007fa6e23ff7da in vrb_add_credits (ep_fid=0x18aa5e0, credits=18446744073709551615)
at prov/verbs/src/verbs_ep.c:49
49 cq->cq_fastlock_acquire(&cq->cq_lock);
[Current thread is 1 (Thread 0x7fa6e5062c40 (LWP 13355))]
(gdb) bt
#0 0x00007fa6e23ff7da in vrb_add_credits (ep_fid=0x18aa5e0, credits=18446744073709551615)
at prov/verbs/src/verbs_ep.c:49
#1 0x00007fa6e2423f97 in rxm_handle_credit (rxm_ep=0x18ab580, rx_buf=0x7fa6dcb1f510) at prov/rxm/src/rxm_cq.c:1334
#2 0x00007fa6e24242fd in rxm_handle_comp (rxm_ep=0x18ab580, comp=0x7ffe6fc05b30) at prov/rxm/src/rxm_cq.c:1414
#3 0x00007fa6e24256e8 in rxm_ep_do_progress (util_ep=0x18ab580) at prov/rxm/src/rxm_cq.c:1723
#4 0x00007fa6e24258a3 in rxm_ep_progress (util_ep=0x18ab580) at prov/rxm/src/rxm_cq.c:1761
#5 0x00007fa6e23a60e2 in ofi_cq_progress (cq=0x18a3820) at prov/util/src/util_cq.c:599
#6 0x00007fa6e23a5311 in ofi_cq_readfrom (cq_fid=0x18a3820, buf=0x7ffe6fc05e90, count=8, src_addr=0x0)
at prov/util/src/util_cq.c:247
#7 0x00007fa6e23a5601 in ofi_cq_read (cq_fid=0x18a3820, buf=0x7ffe6fc05e90, count=8) at prov/util/src/util_cq.c:314
#8 0x00007fa6e3c3478a in MPIR_Waitall_impl () from /scratch/jenkins/builds/mpich/stable/lib/libmpi.so.12
#9 0x00007fa6e3c5cb5a in MPIR_Waitall () from /scratch/jenkins/builds/mpich/stable/lib/libmpi.so.12
#10 0x00007fa6e3c5da8e in PMPI_Waitall () from /scratch/jenkins/builds/mpich/stable/lib/libmpi.so.12
#11 0x0000000000401751 in main (argc=, argv=) at osu_bw.c:137
(gdb)l
44 struct util_cq *cq;
45
46 ep = container_of(ep_fid, struct vrb_ep, util_ep.ep_fid);
47 cq = ep->util_ep.tx_cq;
48
49 cq->cq_fastlock_acquire(&cq->cq_lock);
50 ep->peer_rq_credits += credits;
51 cq->cq_fastlock_release(&cq->cq_lock);
52 }
53
(gdb) p cq
$1 = (struct util_cq *) 0x0
(gdb)
(gdb) p *ep
$1 = {util_ep = {ep_fid = {fid = {fclass = 6, context = 0x0, ops = 0x7fa6e2688d40 <vrb_srq_ep_ops>},
ops = 0x7fa6e2688b60 <vrb_srq_ep_base_ops>, cm = 0x7fa6e2688ba0 <vrb_srq_cm_ops>,
msg = 0x7fa6e2688940 <vrb_srq_msg_ops>, rma = 0x7fa6e2688c00 <vrb_srq_rma_ops>, tagged = 0x0,
atomic = 0x7fa6e2688c60 <vrb_srq_atomic_ops>, collective = 0x0}, domain = 0x18ab1a8, av = 0x18a8a80, av_entry = {
next = 0x18a6390, prev = 0x100000001}, eq = 0x0, rx_cq = 0x0, rx_op_flags = 0, tx_cq = 0x0, tx_op_flags = 0,
inject_op_flags = 0, tx_msg_flags = 0, rx_msg_flags = 0, tx_cntr = 0x0, rx_cntr = 0x0, rd_cntr = 0x0,
wr_cntr = 0x21, rem_rd_cntr = 0x7fa6e2c60030 <_IO_wmem_jumps+144>, rem_wr_cntr = 0x18a6410, tx_cntr_inc = 0x20,
rx_cntr_inc = 0x21, rd_cntr_inc = 0x7362726576, wr_cntr_inc = 0x6d617267, rem_rd_cntr_inc = 0x18aa780,
rem_wr_cntr_inc = 0x91, type = 25920544, caps = 25920544, flags = 112, progress = 0x400, lock = {impl = 24205392,
is_initialized = 0, in_use = 1}, lock_acquire = 0x1c070, lock_release = 0x1c000, coll_cid_mask = 0x50,
coll_ready_queue = {head = 0x10, tail = 0x0}}, ibv_qp = 0x400, sq_credits = 0, peer_rq_credits = 0,
rq_credits_avail = 0, threshold = 0, {id = 0x6, {ep_name = {gid = {
raw = "\006\000\000\000\000\000\000\000A\000\000\000\000\000\000", global = {subnet_prefix = 6,
interface_id = 65}}, qpn = 25784960, lid = 0, pkey = 0, service = 34320, sl = 138 '\212',
padding = "\001\000\000\000"}, service = 25849728}}, inject_limit = 25849696, eq = 0x0, srq_ep = 0x1897650,
info = 0x0, wrs = 0x91, rx_cq_size = 0, conn_param = {private_data = 0x0, private_data_len = 144 '\220',
responder_resources = 0 '\000', initiator_depth = 0 '\000', flow_control = 0 '\000', retry_count = 0 '\000',
rnr_retry_count = 0 '\000', srq = 0 '\000', qp_num = 0}, cm_hdr = 0x0, cm_priv_data = 0x0}
(gdb)