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vmbus: refactor hv_signal_on_read

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The function hv_signal_on_read was defined in hyperv.h and
only used in one place in ring_buffer code. Clearer to just
move it inline there.

Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Stephen Hemminger
2017-06-25 12:30:26 -07:00
committed by Greg Kroah-Hartman
parent 95c40f41cf
commit 8dd45f2ab0
2 changed files with 30 additions and 51 deletions
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32
drivers/hv/ring_buffer.c
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@@ -29,6 +29,7 @@
#include <linux/uio.h>
#include <linux/vmalloc.h>
#include <linux/slab.h>
#include <linux/prefetch.h>
#include "hyperv_vmbus.h"
@@ -357,7 +358,7 @@ struct vmpacket_descriptor *hv_pkt_iter_first(struct vmbus_channel *channel)
{
struct hv_ring_buffer_info *rbi = &channel->inbound;
/* set state for later hv_signal_on_read() */
/* set state for later hv_pkt_iter_close */
rbi->cached_read_index = rbi->ring_buffer->read_index;
if (hv_pkt_iter_avail(rbi) < sizeof(struct vmpacket_descriptor))
@@ -400,6 +401,8 @@ EXPORT_SYMBOL_GPL(__hv_pkt_iter_next);
void hv_pkt_iter_close(struct vmbus_channel *channel)
{
struct hv_ring_buffer_info *rbi = &channel->inbound;
u32 cur_write_sz, cached_write_sz;
u32 pending_sz;
/*
* Make sure all reads are done before we update the read index since
@@ -409,6 +412,31 @@ void hv_pkt_iter_close(struct vmbus_channel *channel)
virt_rmb();
rbi->ring_buffer->read_index = rbi->priv_read_index;
hv_signal_on_read(channel);
/*
* Issue a full memory barrier before making the signaling decision.
* Here is the reason for having this barrier:
* If the reading of the pend_sz (in this function)
* were to be reordered and read before we commit the new read
* index (in the calling function) we could
* have a problem. If the host were to set the pending_sz after we
* have sampled pending_sz and go to sleep before we commit the
* read index, we could miss sending the interrupt. Issue a full
* memory barrier to address this.
*/
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)
return;
cur_write_sz = hv_get_bytes_to_write(rbi);
if (cur_write_sz < pending_sz)
return;
cached_write_sz = hv_get_cached_bytes_to_write(rbi);
if (cached_write_sz < pending_sz)
vmbus_setevent(channel);
}
EXPORT_SYMBOL_GPL(hv_pkt_iter_close);