sfc: Correct and expand some comments
These comments have been revised in response to questions raised by Andrew Morton in <20080501120858.207b6dd6.akpm@linux-foundation.org>. Signed-off-by: Ben Hutchings <bhutchings@solarflare.com> Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
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@ -199,11 +199,12 @@ static inline int efx_process_channel(struct efx_channel *channel, int rx_quota)
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*/
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static inline void efx_channel_processed(struct efx_channel *channel)
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{
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/* Write to EVQ_RPTR_REG. If a new event arrived in a race
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* with finishing processing, a new interrupt will be raised.
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*/
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/* The interrupt handler for this channel may set work_pending
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* as soon as we acknowledge the events we've seen. Make sure
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* it's cleared before then. */
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channel->work_pending = 0;
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smp_wmb(); /* Ensure channel updated before any new interrupt. */
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smp_wmb();
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falcon_eventq_read_ack(channel);
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}
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@ -427,9 +428,12 @@ static void efx_start_channel(struct efx_channel *channel)
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netif_napi_add(channel->napi_dev, &channel->napi_str,
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efx_poll, napi_weight);
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/* The interrupt handler for this channel may set work_pending
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* as soon as we enable it. Make sure it's cleared before
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* then. Similarly, make sure it sees the enabled flag set. */
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channel->work_pending = 0;
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channel->enabled = 1;
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smp_wmb(); /* ensure channel updated before first interrupt */
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smp_wmb();
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napi_enable(&channel->napi_str);
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@ -1332,13 +1336,17 @@ static int efx_net_stop(struct net_device *net_dev)
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return 0;
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}
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/* Context: process, dev_base_lock held, non-blocking. */
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/* Context: process, dev_base_lock or RTNL held, non-blocking. */
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static struct net_device_stats *efx_net_stats(struct net_device *net_dev)
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{
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struct efx_nic *efx = net_dev->priv;
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struct efx_mac_stats *mac_stats = &efx->mac_stats;
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struct net_device_stats *stats = &net_dev->stats;
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/* Update stats if possible, but do not wait if another thread
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* is updating them (or resetting the NIC); slightly stale
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* stats are acceptable.
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*/
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if (!spin_trylock(&efx->stats_lock))
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return stats;
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if (efx->state == STATE_RUNNING) {
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