Commit da01f60f authored by Pavel Begunkov's avatar Pavel Begunkov Committed by Jens Axboe
Browse files

io_uring/eventfd: clean up rcu locking 



Conditional locking is never welcome if there are better options. Move
rcu locking into io_eventfd_signal(), make it unconditional and use
guards. It also helps with sparse warnings.

Signed-off-by: default avatarPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/91a925e708ca8a5aa7fee61f96d29b24ea9adeaf.1745493845.git.asml.silence@gmail.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 62f666df

io_uring/eventfd.c

+7 −17
Original line number Diff line number Diff line
@@ -47,13 +47,6 @@ static void io_eventfd_do_signal(struct rcu_head *rcu) 
	io_eventfd_put(ev_fd);

}



static void io_eventfd_release(struct io_ev_fd *ev_fd, bool put_ref)

{

	if (put_ref)

		io_eventfd_put(ev_fd);

	rcu_read_unlock();

}



/*

 * Returns true if the caller should put the ev_fd reference, false if not.

 */
@@ -89,11 +82,6 @@ static struct io_ev_fd *io_eventfd_grab(struct io_ring_ctx *ctx) 
{

	struct io_ev_fd *ev_fd;



	if (READ_ONCE(ctx->rings->cq_flags) & IORING_CQ_EVENTFD_DISABLED)

		return NULL;



	rcu_read_lock();



	/*

	 * rcu_dereference ctx->io_ev_fd once and use it for both for checking

	 * and eventfd_signal
@@ -108,15 +96,18 @@ static struct io_ev_fd *io_eventfd_grab(struct io_ring_ctx *ctx) 
	if (io_eventfd_trigger(ev_fd) && refcount_inc_not_zero(&ev_fd->refs))

		return ev_fd;



	rcu_read_unlock();

	return NULL;

}



void io_eventfd_signal(struct io_ring_ctx *ctx, bool cqe_event)

{

	bool skip = false, put_ref = true;

	bool skip = false;

	struct io_ev_fd *ev_fd;



	if (READ_ONCE(ctx->rings->cq_flags) & IORING_CQ_EVENTFD_DISABLED)

		return;



	guard(rcu)();

	ev_fd = io_eventfd_grab(ctx);

	if (!ev_fd)

		return;
@@ -137,9 +128,8 @@ void io_eventfd_signal(struct io_ring_ctx *ctx, bool cqe_event) 
		spin_unlock(&ctx->completion_lock);

	}



	if (!skip)

		put_ref = __io_eventfd_signal(ev_fd);

	io_eventfd_release(ev_fd, put_ref);

	if (skip || __io_eventfd_signal(ev_fd))

		io_eventfd_put(ev_fd);

}



int io_eventfd_register(struct io_ring_ctx *ctx, void __user *arg,