NAME

       io_uring_prep_futex_wait - prepare a futex wait request

SYNOPSIS

       #include <linux/futex.h>
       #include <unistd.h>
       #include <liburing.h>

       void io_uring_prep_futex_wait(struct io_uring_sqe *sqe,
                                     uint32_t *futex,
                                     uint64_t val,
                                     uint64_t mask,
                                     uint32_t futex_flags,
                                     unsigned int flags);

DESCRIPTION

       The io_uring_prep_futex_wait(3) function prepares a futex wait request. The submission queue entry sqe is
       setup  for waiting on a futex at address futex and which still has the value val and with futex2(2) flags
       of futex_flags and io_uring futex flags of flags .

       mask can be set to a specific bitset mask, which will be matched by the waking side to decide who to wake
       up. To always get woken, an application may use FUTEX_BITSET_MATCH_ANY .

       futex_flags follows the futex2(2) flags, not the futex(2) v1 interface flags.

       flags are currently unused and hence 0 must be passed.

       This function prepares an async futex(2) wait request. See that man  page  for  details.  Note  that  the
       io_uring  futex  wait  request  is  similar to the FUTEX_WAIT_BITSET operation, as FUTEX_WAIT is a strict
       subset of that.

       Available since kernel 6.7.

RETURN VALUE

       None

ERRORS

       The CQE res field will contain the result of the operation. See the  related  man  page  for  details  on
       possible  values. Note that where synchronous system calls will return -1 on failure and set errno to the
       actual error value, io_uring never uses errno.  Instead it returns the negated errno directly in the  CQE
       res field.

NOTES

       Unlike  the  sync futex syscalls that wait on a futex, io_uring does not support passing in a timeout for
       the request. Instead, applications are encouraged to use a linked timeout to abort the futex request at a
       given time, if desired.

SEE ALSO

       io_uring_get_sqe(3),   io_uring_submit(3),   io_uring_prep_futex_waitv(3),   io_uring_prep_futex_wake(3),
       io_uring_prep_link_timeout(3), futex(2) futex2(2)

liburing-2.5                                      Sep 29, 2023                       io_uring_prep_futex_wait(3)