1io_uring_prep_msg_ring(3)       liburing Manual      io_uring_prep_msg_ring(3)
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NAME

6       io_uring_prep_msg_ring - send a message to another ring
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SYNOPSIS

9       #include <liburing.h>
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11       void io_uring_prep_msg_ring(struct io_uring_sqe *sqe,
12                               int fd,
13                               unsigned int len,
14                               __u64 data,
15                               unsigned int flags);
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DESCRIPTION

18       io_uring_prep_msg_ring(3)  prepares a to send a CQE to an io_uring file
19       descriptor. The submission queue entry sqe is setup to use the file de‐
20       scriptor  fd,  which must identify a io_uring context, to post a CQE on
21       that ring where the target CQE res field will contain  the  content  of
22       len  and  the  user_data of data with the request modifier flags set by
23       flags.  Currently there are no valid flag modifiers,  this  field  must
24       contain 0.
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26       The targeted ring may be any ring that the user has access to, even the
27       ring itself. This request can be used for simple message passing to an‐
28       other  ring,  allowing 32+64 bits of data to be transferred through the
29       len and data fields. The use case may be anything from simply waking up
30       someone  waiting  on  the targeted ring, or it can be used to pass mes‐
31       sages between the two rings.
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RETURN VALUE

35       None
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ERRORS

39       These are the errors that are reported in the CQE res field.
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41       -ENOMEM
42              The kernel was unable to allocate memory for the request.
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44       -EINVAL
45              One of the fields set in the SQE was invalid.
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47       -EBADFD
48              The descriptor passed in fd does not refer to an  io_uring  file
49              descriptor.
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51       -EOVERFLOW
52              The kernel was unable to fill a CQE on the target ring. This can
53              happen if the target CQ ring is in an  overflow  state  and  the
54              kernel wasn't able to allocate memory for a new CQE entry.
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58liburing-2.2                    March 10, 2022       io_uring_prep_msg_ring(3)
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