1IBV_POLL_CQ(3)          Libibverbs Programmer's Manual          IBV_POLL_CQ(3)
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NAME

6       ibv_poll_cq - poll a completion queue (CQ)
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SYNOPSIS

9       #include <infiniband/verbs.h>
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11       int ibv_poll_cq(struct ibv_cq *cq, int num_entries,
12                       struct ibv_wc *wc);
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DESCRIPTION

15       ibv_poll_cq()  polls  the  CQ  cq  for work completions and returns the
16       first num_entries (or all available  completions  if  the  CQ  contains
17       fewer  than this number) in the array wc.  The argument wc is a pointer
18       to an array of ibv_wc structs, as defined in <infiniband/verbs.h>.
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20       struct ibv_wc {
21               uint64_t                wr_id;          /* ID of the completed Work Request (WR) */
22               enum ibv_wc_status      status;         /* Status of the operation */
23               enum ibv_wc_opcode      opcode;         /* Operation type specified in the completed WR */
24               uint32_t                vendor_err;     /* Vendor error syndrome */
25               uint32_t                byte_len;       /* Number of bytes transferred */
26               uint32_t                imm_data;       /* Immediate data (in network byte order) */
27               uint32_t                qp_num;         /* Local QP number of completed WR */
28               uint32_t                src_qp;         /* Source QP number (remote QP number) of completed WR (valid only for UD QPs) */
29               int                     wc_flags;       /* Flags of the completed WR */
30               uint16_t                pkey_index;     /* P_Key index (valid only for GSI QPs) */
31               uint16_t                slid;           /* Source LID */
32               uint8_t                 sl;             /* Service Level */
33               uint8_t                 dlid_path_bits; /* DLID path bits (not applicable for multicast messages) */
34       };
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37       The attribute wc_flags describes the properties of the work completion.
38       It is either 0 or the bitwise OR of one or more of the following flags:
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40       IBV_WC_GRH  GRH is present (valid only for UD QPs)
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42       IBV_WC_WITH_IMM  Immediate data value is valid
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44       Not  all  wc  attributes  are always valid. If the completion status is
45       other than IBV_WC_SUCCESS, only the  following  attributes  are  valid:
46       wr_id, status, qp_num, and vendor_err.
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RETURN VALUE

49       On  success,  ibv_poll_cq()  returns  a non-negative value equal to the
50       number of completions found.  On failure, a negative value is returned.
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NOTES

53       Each polled completion is removed from the CQ and cannot be returned to
54       it.
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56       The  user  should  consume  work completions at a rate that prevents CQ
57       overrun from occurrence.  In case of a  CQ  overrun,  the  async  event
58       IBV_EVENT_CQ_ERR will be triggered, and the CQ cannot be used.
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SEE ALSO

61       ibv_post_send(3), ibv_post_recv(3)
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AUTHORS

64       Dotan Barak <dotanba@gmail.com>
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68libibverbs                        2006-10-31                    IBV_POLL_CQ(3)