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Annotate lockless reads in homa_qdisc_deferred_offset #148

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Annotate lockless reads in homa_qdisc_deferred_offset #148

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4 changes: 2 additions & 2 deletions homa_qdisc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -753,7 +753,7 @@ void homa_qdisc_defer_homa(struct homa_qdisc_dev *qdev, struct sk_buff *skb)
h = (struct homa_data_hdr *)skb_transport_header(skb);
bytes_left = rpc->msgout.length - ntohl(h->seg.offset);
if (bytes_left < rpc->qrpc.tx_left)
rpc->qrpc.tx_left = bytes_left;
WRITE_ONCE(rpc->qrpc.tx_left, bytes_left);
rpc->qrpc.qdev = qdev;
homa_qdisc_insert_rb(qdev, rpc);
}
Expand Down Expand Up @@ -950,7 +950,7 @@ struct sk_buff *homa_qdisc_get_deferred_homa(struct homa_qdisc_dev *qdev)
bytes_left = rpc->msgout.length - (ntohl(h->seg.offset) +
info->data_bytes);
if (bytes_left < qrpc->tx_left)
qrpc->tx_left = bytes_left;
WRITE_ONCE(qrpc->tx_left, bytes_left);
if (fifo) {
if (skb_queue_len(&qrpc->packets) > 0) {
rb_erase_cached(node, &qdev->deferred_rpcs);
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7 changes: 4 additions & 3 deletions homa_qdisc.h
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Original file line number Diff line number Diff line change
Expand Up @@ -484,10 +484,11 @@ static inline bool homa_qdisc_precedes(struct homa_rpc *rpc1,
static inline int homa_qdisc_deferred_offset(struct homa_rpc *rpc)
{
/* This doesn't synchronize, but the worst that can happen is
* to return a slightly out-of-date result.
* to return a slightly out-of-date result. The pacer modifies
* these fields concurrently, under qdev->defer_lock.
*/
if (skb_queue_len(&rpc->qrpc.packets) > 0)
return rpc->msgout.length - rpc->qrpc.tx_left;
if (skb_queue_len_lockless(&rpc->qrpc.packets) > 0)
return rpc->msgout.length - READ_ONCE(rpc->qrpc.tx_left);
return -1;
}

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