Commit f4bb2f65 authored by Jens Axboe's avatar Jens Axboe
Browse files

io_uring/eventfd: move ctx->evfd_last_cq_tail into io_ev_fd 

Everything else about the io_uring eventfd support is nicely kept
private to that code, except the cached_cq_tail tracking. With
everything else in place, move io_eventfd_flush_signal() to using
the ev_fd grab+release helpers, which then enables the direct use of
io_ev_fd for this tracking too.

Link: https://lore.kernel.org/r/20240921080307.185186-7-axboe@kernel.dk


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 83a4f865

io_uring/eventfd.c

+29 −21
Original line number Diff line number Diff line
@@ -13,10 +13,12 @@ 


struct io_ev_fd {

	struct eventfd_ctx	*cq_ev_fd;

	unsigned int		eventfd_async: 1;

	struct rcu_head		rcu;

	unsigned int		eventfd_async;

	/* protected by ->completion_lock */

	unsigned		last_cq_tail;

	refcount_t		refs;

	atomic_t		ops;

	struct rcu_head		rcu;

};



enum {
@@ -123,25 +125,31 @@ void io_eventfd_signal(struct io_ring_ctx *ctx) 


void io_eventfd_flush_signal(struct io_ring_ctx *ctx)

{

	bool skip;

	struct io_ev_fd *ev_fd;



	spin_lock(&ctx->completion_lock);

	ev_fd = io_eventfd_grab(ctx);

	if (ev_fd) {

		bool skip, put_ref = true;



		/*

	 * Eventfd should only get triggered when at least one event has been

	 * posted. Some applications rely on the eventfd notification count

	 * only changing IFF a new CQE has been added to the CQ ring. There's

	 * no depedency on 1:1 relationship between how many times this

	 * function is called (and hence the eventfd count) and number of CQEs

	 * posted to the CQ ring.

		 * Eventfd should only get triggered when at least one event

		 * has been posted. Some applications rely on the eventfd

		 * notification count only changing IFF a new CQE has been

		 * added to the CQ ring. There's no dependency on 1:1

		 * relationship between how many times this function is called

		 * (and hence the eventfd count) and number of CQEs posted to

		 * the CQ ring.

		 */

	skip = ctx->cached_cq_tail == ctx->evfd_last_cq_tail;

	ctx->evfd_last_cq_tail = ctx->cached_cq_tail;

		spin_lock(&ctx->completion_lock);

		skip = ctx->cached_cq_tail == ev_fd->last_cq_tail;

		ev_fd->last_cq_tail = ctx->cached_cq_tail;

		spin_unlock(&ctx->completion_lock);

	if (skip)

		return;



	io_eventfd_signal(ctx);

		if (!skip)

			put_ref = __io_eventfd_signal(ev_fd);



		io_eventfd_release(ev_fd, put_ref);

	}

}



int io_eventfd_register(struct io_ring_ctx *ctx, void __user *arg,
@@ -172,7 +180,7 @@ int io_eventfd_register(struct io_ring_ctx *ctx, void __user *arg, 
	}



	spin_lock(&ctx->completion_lock);

	ctx->evfd_last_cq_tail = ctx->cached_cq_tail;

	ev_fd->last_cq_tail = ctx->cached_cq_tail;

	spin_unlock(&ctx->completion_lock);



	ev_fd->eventfd_async = eventfd_async;