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authorPaul Durrant <Paul.Durrant@citrix.com>2013-12-11 05:57:16 -0500
committerDavid S. Miller <davem@davemloft.net>2013-12-12 13:35:38 -0500
commitd9601a36ffdb5c142697bef1228afb5ba4ee4003 (patch)
tree0ab7a3fba3e2c7f238a6f33d5eeaf9d360ddd37d
parent10574059ce0451c6572c85329c772aa15085f8eb (diff)
xen-netback: napi: don't prematurely request a tx event
This patch changes the RING_FINAL_CHECK_FOR_REQUESTS in xenvif_build_tx_gops to a check for RING_HAS_UNCONSUMED_REQUESTS as the former call has the side effect of advancing the ring event pointer and therefore inviting another interrupt from the frontend before the napi poll has actually finished, thereby defeating the point of napi. The event pointer is updated by RING_FINAL_CHECK_FOR_REQUESTS in xenvif_poll, the napi poll function, if the work done is less than the budget i.e. when actually transitioning back to interrupt mode. Reported-by: Malcolm Crossley <malcolm.crossley@citrix.com> Signed-off-by: Paul Durrant <paul.durrant@citrix.com> Cc: Wei Liu <wei.liu2@citrix.com> Cc: Ian Campbell <ian.campbell@citrix.com> Cc: David Vrabel <david.vrabel@citrix.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--drivers/net/xen-netback/netback.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index db79e29b3d09..33b8aa612d13 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -1475,7 +1475,7 @@ static unsigned xenvif_tx_build_gops(struct xenvif *vif, int budget)
1475 continue; 1475 continue;
1476 } 1476 }
1477 1477
1478 RING_FINAL_CHECK_FOR_REQUESTS(&vif->tx, work_to_do); 1478 work_to_do = RING_HAS_UNCONSUMED_REQUESTS(&vif->tx);
1479 if (!work_to_do) 1479 if (!work_to_do)
1480 break; 1480 break;
1481 1481