static __poll_t dma_buf_poll()

in dma-buf.c [230:298]

• 49 lines of code
• 12 McCabe index (conditional complexity)

static __poll_t dma_buf_poll(struct file *file, poll_table *poll)
{
	struct dma_buf *dmabuf;
	struct dma_resv *resv;
	__poll_t events;

	dmabuf = file->private_data;
	if (!dmabuf || !dmabuf->resv)
		return EPOLLERR;

	resv = dmabuf->resv;

	poll_wait(file, &dmabuf->poll, poll);

	events = poll_requested_events(poll) & (EPOLLIN | EPOLLOUT);
	if (!events)
		return 0;

	dma_resv_lock(resv, NULL);

	if (events & EPOLLOUT) {
		struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_out;

		/* Check that callback isn't busy */
		spin_lock_irq(&dmabuf->poll.lock);
		if (dcb->active)
			events &= ~EPOLLOUT;
		else
			dcb->active = EPOLLOUT;
		spin_unlock_irq(&dmabuf->poll.lock);

		if (events & EPOLLOUT) {
			/* Paired with fput in dma_buf_poll_cb */
			get_file(dmabuf->file);

			if (!dma_buf_poll_add_cb(resv, true, dcb))
				/* No callback queued, wake up any other waiters */
				dma_buf_poll_cb(NULL, &dcb->cb);
			else
				events &= ~EPOLLOUT;
		}
	}

	if (events & EPOLLIN) {
		struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_in;

		/* Check that callback isn't busy */
		spin_lock_irq(&dmabuf->poll.lock);
		if (dcb->active)
			events &= ~EPOLLIN;
		else
			dcb->active = EPOLLIN;
		spin_unlock_irq(&dmabuf->poll.lock);

		if (events & EPOLLIN) {
			/* Paired with fput in dma_buf_poll_cb */
			get_file(dmabuf->file);

			if (!dma_buf_poll_add_cb(resv, false, dcb))
				/* No callback queued, wake up any other waiters */
				dma_buf_poll_cb(NULL, &dcb->cb);
			else
				events &= ~EPOLLIN;
		}
	}

	dma_resv_unlock(resv);
	return events;
}