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io_uring: return normal tw run linking optimisation

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io_submit_flush_completions() may produce new task_work items, so it's a
good idea to recheck the task_work list after flushing completions. The
optimisation is not new and was accidentially removed by
f88262e60b ("io_uring: lockless task list")

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/a7ed5ede84de190832cc33ebbcdd6e91cd90f5b6.1674484266.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2023-01-23 14:37:19 +00:00 committed by Jens Axboe
parent cb6bf7f285
commit 50470fc572
1 changed files with 9 additions and 0 deletions
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9
io_uring/io_uring.c
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@ -1238,6 +1238,15 @@ void tctx_task_work(struct callback_head *cb)
loops++;
node = io_llist_xchg(&tctx->task_list, &fake);
count += handle_tw_list(node, &ctx, &uring_locked, &fake);
/* skip expensive cmpxchg if there are items in the list */
if (READ_ONCE(tctx->task_list.first) != &fake)
continue;
if (uring_locked && !wq_list_empty(&ctx->submit_state.compl_reqs)) {
io_submit_flush_completions(ctx);
if (READ_ONCE(tctx->task_list.first) != &fake)
continue;
}
node = io_llist_cmpxchg(&tctx->task_list, &fake, NULL);
} while (node != &fake);