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

       ibv_poll_cq - poll a completion queue (CQ)

       #include <infiniband/verbs.h>

       int ibv_poll_cq(struct ibv_cq *cq, int num_entries,
                       struct ibv_wc *wc);

       ibv_poll_cq()  polls the CQ cq for work completions and returns the first num_entries (or all available comple-
       tions if the CQ contains fewer than this number) in the array wc.  The argument wc is a pointer to an array  of
       ibv_wc structs, as defined in <infiniband/verbs.h>.

       struct ibv_wc {
               uint64_t                wr_id;          /* ID of the completed Work Request (WR) */
               enum ibv_wc_status      status;         /* Status of the operation */
               enum ibv_wc_opcode      opcode;         /* Operation type specified in the completed WR */
               uint32_t                vendor_err;     /* Vendor error syndrome */
               uint32_t                byte_len;       /* Number of bytes transferred */
               uint32_t                imm_data;       /* Immediate data (in network byte order) */
               uint32_t                qp_num;         /* Local QP number of completed WR */
               uint32_t                src_qp;         /* Source QP number (remote QP number) of completed WR (valid only for UD QPs) */
               int                     wc_flags;       /* Flags of the completed WR */
               uint16_t                pkey_index;     /* P_Key index (valid only for GSI QPs) */
               uint16_t                slid;           /* Source LID */
               uint8_t                 sl;             /* Service Level */
               uint8_t                 dlid_path_bits; /* DLID path bits (not applicable for multicast messages) */

       The  attribute  wc_flags  describes the properties of the work completion.  It is either 0 or the bitwise OR of
       one or more of the following flags:

       IBV_WC_GRH  GRH is present (valid only for UD QPs)

       IBV_WC_WITH_IMM  Immediate data value is valid

       Not all wc attributes are always valid. If the completion status is other than IBV_WC_SUCCESS, only the follow-
       ing attributes are valid: wr_id, status, qp_num, and vendor_err.

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

       Each polled completion is removed from the CQ and cannot be returned to it.

       The user should consume work completions at a rate that prevents CQ overrun from occurrence.  In case of  a  CQ
       overrun, the async event IBV_EVENT_CQ_ERR will be triggered, and the CQ cannot be used.

       ibv_post_send(3), ibv_post_recv(3)

       Dotan Barak <>

libibverbs                        2006-10-31                    IBV_POLL_CQ(3)