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Char/Misc fix for 4.16-rc7 

This is a single hyperv bugfix for 4.16-rc7.
 
 It resolves an issue with the ring-buffer signaling to resolve reported
 problems.
 
 It's been in linux-next for a while now with no reported issues.
 
 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Merge tag 'char-misc-4.16-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc

Pull hyperv fix from Greg KH:
 "This is a single hyperv bugfix for 4.16-rc7.

  It resolves an issue with the ring-buffer signaling to resolve
  reported problems.

  It's been in linux-next for a while now with no reported issues"

* tag 'char-misc-4.16-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc:
  Drivers: hv: vmbus: Fix ring buffer signaling
This commit is contained in:
Linus Torvalds 2018-03-23 11:08:40 -07:00
parent cde00d2169 655296c8bb
commit 97235e74c3
1 changed files with 35 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

40
drivers/hv/ring_buffer.c
View File

@ -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);
}