Confusion regarding the use of OP_TIMEOUT

["Drew DeVault" <sir@cmpwn.com>]

Hi folks! I'm trying to use IO_TIMEOUT to insert a pause in the middle
of my SQ. I set the off (desired number of events to wait for) to zero,
which according to the docs just makes it behave like a timer.

Essentially, I want the following:

[operations...]
OP_TIMEOUT
[operations...]

To be well-ordered, so that the second batch executes after the first.
To accomplish this, I've tried to submit the first operation of the
second batch with IO_DRAIN, which causes the CQE to be delayed, but
ultimately it fails with EINTR instead of just waiting to execute.

I understand that the primary motivator for OP_TIMEOUT is to provide a
timeout functionality for other CQEs. Is my use-case not accomodated by
io_uring?