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authorBen Hutchings <bhutchings@solarflare.com>2008-05-16 21:18:14 +0100
committerJeff Garzik <jgarzik@redhat.com>2008-05-22 05:59:29 -0400
commit5b9e207ced5bb7af98b3c147171893435f5104ca (patch)
tree3ddf00b344697899b608fbb4730e93f3621f22ce /drivers
parent086ea3564a5378a06c7cbfaf9d2727bc58a8c285 (diff)
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>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/net/sfc/efx.c20
1 files changed, 14 insertions, 6 deletions
diff --git a/drivers/net/sfc/efx.c b/drivers/net/sfc/efx.c
index f6131e578b4..11ee0d4407c 100644
--- a/drivers/net/sfc/efx.c
+++ b/drivers/net/sfc/efx.c
@@ -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)
{
- /* Write to EVQ_RPTR_REG. If a new event arrived in a race
- * with finishing processing, a new interrupt will be raised.
- */
+ /* The interrupt handler for this channel may set work_pending
+ * as soon as we acknowledge the events we've seen. Make sure
+ * it's cleared before then. */
channel->work_pending = 0;
- smp_wmb(); /* Ensure channel updated before any new interrupt. */
+ smp_wmb();
+
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,
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->enabled = 1;
- smp_wmb(); /* ensure channel updated before first interrupt */
+ smp_wmb();
napi_enable(&channel->napi_str);
@@ -1332,13 +1336,17 @@ static int efx_net_stop(struct net_device *net_dev)
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)
{
struct efx_nic *efx = net_dev->priv;
struct efx_mac_stats *mac_stats = &efx->mac_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))
return stats;
if (efx->state == STATE_RUNNING) {