Merge tag 'char-misc-4.16-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc (97235e74) · Commits · 戴 / test

drivers/hv/ring_buffer.c

+35 −17

Original line number	Diff line number	Diff line
		@@ -417,13 +417,24 @@ __hv_pkt_iter_next(struct vmbus_channel *channel,
		}
		EXPORT_SYMBOL_GPL(__hv_pkt_iter_next);

		/* How many bytes were read in this iterator cycle */
		static u32 hv_pkt_iter_bytes_read(const struct hv_ring_buffer_info *rbi,
		u32 start_read_index)
		{
		if (rbi->priv_read_index >= start_read_index)
		return rbi->priv_read_index - start_read_index;
		else
		return rbi->ring_datasize - start_read_index +
		rbi->priv_read_index;
		}

		/*
		* Update host ring buffer after iterating over packets.
		*/
		void hv_pkt_iter_close(struct vmbus_channel *channel)
		{
		struct hv_ring_buffer_info *rbi = &channel->inbound;
		u32 orig_write_sz = hv_get_bytes_to_write(rbi);
		u32 curr_write_sz, pending_sz, bytes_read, start_read_index;

		/*
		* Make sure all reads are done before we update the read index since
		@@ -431,8 +442,12 @@ void hv_pkt_iter_close(struct vmbus_channel *channel)
		* is updated.
		*/
		virt_rmb();
		start_read_index = rbi->ring_buffer->read_index;
		rbi->ring_buffer->read_index = rbi->priv_read_index;

		if (!rbi->ring_buffer->feature_bits.feat_pending_send_sz)
		return;

		/*
		* Issue a full memory barrier before making the signaling decision.
		* Here is the reason for having this barrier:
		@@ -446,26 +461,29 @@ void hv_pkt_iter_close(struct vmbus_channel *channel)
		*/
		virt_mb();

		/* If host has disabled notifications then skip */
		if (rbi->ring_buffer->interrupt_mask)
		pending_sz = READ_ONCE(rbi->ring_buffer->pending_send_sz);
		if (!pending_sz)
		return;

		if (rbi->ring_buffer->feature_bits.feat_pending_send_sz) {
		u32 pending_sz = READ_ONCE(rbi->ring_buffer->pending_send_sz);
		/*
		* Ensure the read of write_index in hv_get_bytes_to_write()
		* happens after the read of pending_send_sz.
		*/
		virt_rmb();
		curr_write_sz = hv_get_bytes_to_write(rbi);
		bytes_read = hv_pkt_iter_bytes_read(rbi, start_read_index);

		/*
		* If there was space before we began iteration,
		* then host was not blocked. Also handles case where
		* pending_sz is zero then host has nothing pending
		* and does not need to be signaled.
		* then host was not blocked.
		*/
		if (orig_write_sz > pending_sz)

		if (curr_write_sz - bytes_read > pending_sz)
		return;

		/* If pending write will not fit, don't give false hope. */
		if (hv_get_bytes_to_write(rbi) < pending_sz)
		if (curr_write_sz <= pending_sz)
		return;
		}

		vmbus_setevent(channel);
		}

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