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Re: [Xen-devel] [PATCH] libvchan: Make raw_get_{data_ready, buffer_space} match

On 05/19/2014 07:31 AM, Ian Jackson wrote:
Jason Andryuk writes ("[PATCH] libvchan: Make raw_get_{data_ready,buffer_space} 
For writing into a vchan, raw_get_buffer_space used >, allowing the full
ring size to be written.  On the read side, raw_get_data_ready compared
the ring size with >=.  This mismatch means a completely filled buffer
cannot be read.  Fix this by making the size checks identical.

This seems right to me, but I have CC'd the authors of this area of
code to give them a chance to comment.


This also looks correct to me.

Signed-off-by: Jason Andryuk <andryuk@xxxxxxxx>
  tools/libvchan/io.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/libvchan/io.c b/tools/libvchan/io.c
index 804c63c..6e6e239 100644
--- a/tools/libvchan/io.c
+++ b/tools/libvchan/io.c
@@ -118,7 +118,7 @@ static inline int send_notify(struct libxenvchan *ctrl, 
uint8_t bit)
  static inline int raw_get_data_ready(struct libxenvchan *ctrl)
        uint32_t ready = rd_prod(ctrl) - rd_cons(ctrl);
-       if (ready >= rd_ring_size(ctrl))
+       if (ready > rd_ring_size(ctrl))
                /* We have no way to return errors.  Locking up the ring is
                 * better than the alternatives. */
                return 0;

Daniel De Graaf
National Security Agency

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