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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | SEE ALSO | COLOPHON |
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io_uring_re...er_sync_msg(3) liburing Manual io_uring_re...er_sync_msg(3)
io_uring_register_sync_msg - send a synchronous message to another
ring
#include <liburing.h>
int io_uring_register_sync_msg(struct io_uring_sqe *sqe);
io_uring_register_sync_msg(3) issues a synchronous MSG_RING
request. The sqe parameter must have been cleared and initialized
with io_uring_prep_msg_ring(3).
Normally message requests are sent from one ring to another ring.
But there are also cases where a source ring is not available, yet
it would be convenient to send a message to a destination ring.
io_uring_register_sync_msg(3) exists for that purpose. A source
ring is not required to send a message to another ring, instead
the sqe parameter can be placed on the stack and filled in using
the normal message helpers, and then io_uring_register_sync_msg(3)
can be called. Since a source ring does not exist, the results of
the operation is returned directly rather than via a CQE. On the
destination/receiving end, a CQE is posted, as it would have been
with a non-sync request.
Only data request are supported, sending files such as setup by
io_uring_prep_msg_ring_fd(3) is not supported. The given SQE
should be initialized by io_uring_prep_msg_ring(3) or
io_uring_prep_msg_ring_cqe_flags(3), or any other helper that sets
up a non-fd message request.
The targeted ring may be any ring that the user has access to,
even the ring itself. This request can be used for simple message
passing to another ring, allowing 32+64 bits of data to be
transferred through the len and data fields. The use case may be
anything from simply waking up someone waiting on the targeted
ring, or it can be used to pass messages between the two rings.
io_uring_prep_msg_ring_cqe_flags(3) is similar to
io_uring_prep_msg_ring(3). But has an addition cqe_flags
parameter, which is used to set flags field on CQE side. That way,
you can set the CQE flags field cqe->flags when sending a message.
Be aware that io_uring could potentially set additional bits into
this field.
Available since kernel 6.13.
Returns 0 on success, or -errno on error.
io_uring_prep_msg_ring_cqe_flags(3), io_uring_prep_msg_ring(3)
This page is part of the liburing (A library for io_uring)
project. Information about the project can be found at
⟨https://github.com/axboe/liburing⟩. If you have a bug report for
this manual page, send it to io-uring@vger.kernel.org. This page
was obtained from the project's upstream Git repository
⟨https://github.com/axboe/liburing⟩ on 2025-08-11. (At that time,
the date of the most recent commit that was found in the
repository was 2025-08-02.) 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
liburing-2.11 July 10, 2025 io_uring_re...er_sync_msg(3)
Pages that refer to this page: io_uring_register_sync_msg(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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