io_uring: remove racy overflow list fast checks (9cd2be51) · Commits · 戴 / test

list_empty_careful() is not racy only if some conditions are met, i.e. no re-adds after del_init. io_cqring_overflow_flush() does list_move(), so it's actually racy. Remove those checks, we have ->cq_check_overflow for the fast path. Signed-off-by:

Pavel Begunkov <asml.silence@gmail.com> Signed-off-by:

Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

+1 −4

Original line number	Diff line number	Diff line
		@@ -1724,8 +1724,6 @@ static bool io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool force,
		LIST_HEAD(list);

		if (!force) {
		if (list_empty_careful(&ctx->cq_overflow_list))
		return true;
		if ((ctx->cached_cq_tail - READ_ONCE(rings->cq.head) ==
		rings->cq_ring_entries))
		return false;
		@@ -6822,8 +6820,7 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr)

		/* if we have a backlog and couldn't flush it all, return BUSY */
		if (test_bit(0, &ctx->sq_check_overflow)) {
		if (!list_empty(&ctx->cq_overflow_list) &&
		!io_cqring_overflow_flush(ctx, false, NULL, NULL))
		if (!io_cqring_overflow_flush(ctx, false, NULL, NULL))
		return -EBUSY;
		}

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