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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | SEE ALSO | AUTHORS | COLOPHON |
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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 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
<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 */
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.
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_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.
ibv_post_send(3), ibv_post_recv(3)
Dotan Barak <dotanba@gmail.com>
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 2025-08-11. (At
that time, the date of the most recent commit that was found in
the repository was 2025-08-04.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
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)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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