io_uring: signal registered eventfd to process deferred task work

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Some workloads rely on a registered eventfd (via
io_uring_register_eventfd(3)) in order to wake up and process the
io_uring.

In the case of a ring setup with IORING_SETUP_DEFER_TASKRUN, that eventfd
also needs to be signalled when there are tasks to run.

This changes an old behaviour which assumed 1 eventfd signal implied at
least 1 CQE, however only when this new flag is set (and so old users will
not notice). This should be expected with the IORING_SETUP_DEFER_TASKRUN
flag as it is not guaranteed that every task will result in a CQE.

Signed-off-by: Dylan Yudaken <dylany@fb.com>
Link: https://lore.kernel.org/r/20220830125013.570060-7-dylany@fb.com
[axboe: fold in call_rcu() serialization fix]
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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This commit is contained in:

Dylan Yudaken 2022-08-30 05:50:12 -07:00 • committed by Jens Axboe

parent d8e9214f11

commit 21a091b970

2 changed files with 63 additions and 23 deletions

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2

include/linux/io_uring_types.h

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84

io_uring/io_uring.c

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