From 03bad714a1619c0074eb44d6f217c505fe27030f Mon Sep 17 00:00:00 2001 From: Stephen Hemminger Date: Sun, 25 Jun 2017 12:30:28 -0700 Subject: [PATCH] vmbus: more host signalling avoidance Don't signal host if it has disabled interrupts for that ring buffer. Check the feature bit to see if host supports pending send size flag. Signed-off-by: Stephen Hemminger Signed-off-by: K. Y. Srinivasan Signed-off-by: Greg Kroah-Hartman --- drivers/hv/ring_buffer.c | 27 +++++++++++++++++++-------- 1 file changed, 19 insertions(+), 8 deletions(-) diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c index b0f79526b86a..741daa6e2fc7 100644 --- a/drivers/hv/ring_buffer.c +++ b/drivers/hv/ring_buffer.c @@ -396,7 +396,6 @@ 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 pending_sz; /* * Make sure all reads are done before we update the read index since @@ -419,15 +418,27 @@ void hv_pkt_iter_close(struct vmbus_channel *channel) */ virt_mb(); - pending_sz = READ_ONCE(rbi->ring_buffer->pending_send_sz); - /* If the other end is not blocked on write don't bother. */ - if (pending_sz == 0) + /* If host has disabled notifications then skip */ + if (rbi->ring_buffer->interrupt_mask) return; - if (hv_get_bytes_to_write(rbi) < pending_sz) - return; + if (rbi->ring_buffer->feature_bits.feat_pending_send_sz) { + u32 pending_sz = READ_ONCE(rbi->ring_buffer->pending_send_sz); - if (orig_write_sz < pending_sz) - vmbus_setevent(channel); + /* + * 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 pending write will not fit, don't give false hope. */ + if (hv_get_bytes_to_write(rbi) < pending_sz) + return; + } + + vmbus_setevent(channel); } EXPORT_SYMBOL_GPL(hv_pkt_iter_close); -- 2.20.1