diff options
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/hv/ring_buffer.c | 52 |
1 files changed, 35 insertions, 17 deletions
diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c index 50e071444a5c..8699bb969e7e 100644 --- a/drivers/hv/ring_buffer.c +++ b/drivers/hv/ring_buffer.c @@ -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. - */ - if (orig_write_sz > pending_sz) - return; + /* + * If there was space before we began iteration, + * then host was not blocked. + */ - /* If pending write will not fit, don't give false hope. */ - if (hv_get_bytes_to_write(rbi) < pending_sz) - return; - } + if (curr_write_sz - bytes_read > pending_sz) + return; + + /* If pending write will not fit, don't give false hope. */ + if (curr_write_sz <= pending_sz) + return; vmbus_setevent(channel); } |