ibv_poll_cq(3) — Linux manual page


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

NAME         top

       ibv_poll_cq - poll a completion queue (CQ)

SYNOPSIS         top

       #include <infiniband/verbs.h>

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

DESCRIPTION         top

       ibv_poll_cq() polls the CQ cq for work completions and returns
       the first num_entries (or all available completions 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

       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 */
               union {
                       __be32                  imm_data;         /* Immediate data (in network byte order) */
                       uint32_t                invalidated_rkey; /* Local RKey that was invalidated */
               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) */
               unsigned 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

       IBV_WC_WITH_INV  Invalidated RKey data value is valid (cannot be
       combined with IBV_WC_WITH_IMM)

       IBV_WC_IP_CSUM_OK  TCP/UDP checksum over IPv4 and IPv4 header
       checksum are
              verified.  Valid only when device_cap_flags in device_attr
              indicates current QP is supported by checksum offload.

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

RETURN VALUE         top

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

NOTES         top

       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

       IBV_WC_DRIVER1 will be reported as a response to IBV_WR_DRIVER1
       opcode; IBV_WC_DRIVER2/IBV_WC_DRIVER3 will be reported on
       specific driver operations.

SEE ALSO         top

       ibv_post_send(3), ibv_post_recv(3)

AUTHORS         top

       Dotan Barak <dotanba@gmail.com>

COLOPHON         top

       This page is part of the rdma-core (RDMA Core Userspace Libraries
       and Daemons) project.  Information about the project can be found
       at ⟨https://github.com/linux-rdma/rdma-core⟩.  If you have a bug
       report for this manual page, send it to
       linux-rdma@vger.kernel.org.  This page was obtained from the
       project's upstream Git repository
       ⟨https://github.com/linux-rdma/rdma-core.git⟩ on 2023-12-22.  (At
       that time, the date of the most recent commit that was found in
       the repository was 2023-12-20.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
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       (which is not part of the original manual page), send a mail to

libibverbs                     2006-10-31                 IBV_POLL_CQ(3)

Pages that refer to this page: ibv_bind_mw(3)ibv_create_ah_from_wc(3)ibv_get_cq_event(3)ibv_post_recv(3)ibv_post_send(3)ibv_post_srq_recv(3)rdma_get_recv_comp(3)rdma_get_send_comp(3)