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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>
This commit is contained in:
Ben Hutchings 2008-05-16 21:18:14 +01:00 committed by Jeff Garzik
parent 086ea3564a
commit 5b9e207ced
1 changed files with 14 additions and 6 deletions
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20
drivers/net/sfc/efx.c
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@ -199,11 +199,12 @@ static inline int efx_process_channel(struct efx_channel *channel, int rx_quota)
*/ */
static inline void efx_channel_processed(struct efx_channel *channel) static inline void efx_channel_processed(struct efx_channel *channel)
{ {
/* Write to EVQ_RPTR_REG. If a new event arrived in a race /* The interrupt handler for this channel may set work_pending
* with finishing processing, a new interrupt will be raised. * as soon as we acknowledge the events we've seen. Make sure
*/ * it's cleared before then. */
channel->work_pending = 0; channel->work_pending = 0;
smp_wmb(); /* Ensure channel updated before any new interrupt. */ smp_wmb();
falcon_eventq_read_ack(channel); falcon_eventq_read_ack(channel);
} }
@ -427,9 +428,12 @@ static void efx_start_channel(struct efx_channel *channel)
netif_napi_add(channel->napi_dev, &channel->napi_str, netif_napi_add(channel->napi_dev, &channel->napi_str,
efx_poll, napi_weight); efx_poll, napi_weight);
/* The interrupt handler for this channel may set work_pending
* as soon as we enable it. Make sure it's cleared before
* then. Similarly, make sure it sees the enabled flag set. */
channel->work_pending = 0; channel->work_pending = 0;
channel->enabled = 1; channel->enabled = 1;
smp_wmb(); /* ensure channel updated before first interrupt */ smp_wmb();
napi_enable(&channel->napi_str); napi_enable(&channel->napi_str);
@ -1332,13 +1336,17 @@ static int efx_net_stop(struct net_device *net_dev)
return 0; return 0;
} }
/* Context: process, dev_base_lock held, non-blocking. */ /* Context: process, dev_base_lock or RTNL held, non-blocking. */
static struct net_device_stats *efx_net_stats(struct net_device *net_dev) static struct net_device_stats *efx_net_stats(struct net_device *net_dev)
{ {
struct efx_nic *efx = net_dev->priv; struct efx_nic *efx = net_dev->priv;
struct efx_mac_stats *mac_stats = &efx->mac_stats; struct efx_mac_stats *mac_stats = &efx->mac_stats;
struct net_device_stats *stats = &net_dev->stats; struct net_device_stats *stats = &net_dev->stats;
/* Update stats if possible, but do not wait if another thread
* is updating them (or resetting the NIC); slightly stale
* stats are acceptable.
*/
if (!spin_trylock(&efx->stats_lock)) if (!spin_trylock(&efx->stats_lock))
return stats; return stats;
if (efx->state == STATE_RUNNING) { if (efx->state == STATE_RUNNING) {