Mailing List Archive

# HG changeset patch
# User kaf24@firebug.cl.cam.ac.uk
# Node ID bbef89ec44b86b87cd0f108bf5d15a6e2b6562e7
# Parent d24ab5abf85706a71e9e9ac80376ff1fce49a50b
Fix request-notification holdoff in blkback. New code is
more correct and clearer in intent.

Signed-off-by: Keir Fraser <keir@xensource.com>

diff -r d24ab5abf857 -r bbef89ec44b8 linux-2.6-xen-sparse/drivers/xen/blkback/blkback.c
--- a/linux-2.6-xen-sparse/drivers/xen/blkback/blkback.c Sat Dec 3 20:17:11 2005
+++ b/linux-2.6-xen-sparse/drivers/xen/blkback/blkback.c Sat Dec 3 20:53:01 2005
@@ -483,23 +483,22 @@
blkif_back_ring_t *blk_ring = &blkif->blk_ring;
int notify;

+ spin_lock_irqsave(&blkif->blk_ring_lock, flags);
+
/* Place on the response ring for the relevant domain. */
- spin_lock_irqsave(&blkif->blk_ring_lock, flags);
resp = RING_GET_RESPONSE(blk_ring, blk_ring->rsp_prod_pvt);
resp->id = id;
resp->operation = op;
resp->status = st;
blk_ring->rsp_prod_pvt++;
RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(blk_ring, notify);
- spin_unlock_irqrestore(&blkif->blk_ring_lock, flags);

/*
* Tail check for pending requests. Allows frontend to avoid
* notifications if requests are already in flight (lower overheads
* and promotes batching).
*/
- mb();
- if (!__on_blkdev_list(blkif)) {
+ if (blk_ring->rsp_prod_pvt == blk_ring->req_cons) {
int more_to_do;
RING_FINAL_CHECK_FOR_REQUESTS(blk_ring, more_to_do);
if (more_to_do) {
@@ -507,6 +506,8 @@
maybe_trigger_blkio_schedule();
}
}
+
+ spin_unlock_irqrestore(&blkif->blk_ring_lock, flags);

if (notify)
notify_remote_via_irq(blkif->irq);

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