sfc: Remove efx_rx_queue::add_lock

Ensure that efx_fast_push_rx_descriptors() must only run
from efx_process_channel() [NAPI], or when napi_disable()
has been executed.

Reimplement the slow fill by sending an event to the
channel, so that NAPI runs, and hanging the subsequent
fast fill off the event handler. Replace the sfc_refill
workqueue and delayed work items with a timer. We do
not need to stop this timer in efx_flush_all() because
it's safe to send the event always; receiving it will
be delayed until NAPI is restarted.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 37 deletions

diff --git a/drivers/net/sfc/efx.c b/drivers/net/sfc/efx.c
index d1a1d32e73ee..5d9ef05e6abb 100644
--- a/drivers/net/sfc/efx.c
+++ b/drivers/net/sfc/efx.c
@@ -93,13 +93,6 @@ const char *efx_reset_type_names[] = {
 
 #define EFX_MAX_MTU (9 * 1024)
 
-/* RX slow fill workqueue. If memory allocation fails in the fast path,
- * a work item is pushed onto this work queue to retry the allocation later,
- * to avoid the NIC being starved of RX buffers. Since this is a per cpu
- * workqueue, there is nothing to be gained in making it per NIC
- */
-static struct workqueue_struct *refill_workqueue;
-
 /* Reset workqueue. If any NIC has a hardware failure then a reset will be
  * queued onto this work queue. This is not a per-nic work queue, because
  * efx_reset_work() acquires the rtnl lock, so resets are naturally serialised.
@@ -516,11 +509,11 @@ static void efx_start_channel(struct efx_channel *channel)
         channel->enabled = true;
         smp_wmb();
 
-        napi_enable(&channel->napi_str);
-
-        /* Load up RX descriptors */
+        /* Fill the queues before enabling NAPI */
         efx_for_each_channel_rx_queue(rx_queue, channel)
                 efx_fast_push_rx_descriptors(rx_queue);
+
+        napi_enable(&channel->napi_str);
 }
 
 /* This disables event queue processing and packet transmission.
@@ -529,8 +522,6 @@ static void efx_start_channel(struct efx_channel *channel)
  */
 static void efx_stop_channel(struct efx_channel *channel)
 {
-        struct efx_rx_queue *rx_queue;
-
         if (!channel->enabled)
                 return;
 
@@ -538,12 +529,6 @@ static void efx_stop_channel(struct efx_channel *channel)
 
         channel->enabled = false;
         napi_disable(&channel->napi_str);
-
-        /* Ensure that any worker threads have exited or will be no-ops */
-        efx_for_each_channel_rx_queue(rx_queue, channel) {
-                spin_lock_bh(&rx_queue->add_lock);
-                spin_unlock_bh(&rx_queue->add_lock);
-        }
 }
 
 static void efx_fini_channels(struct efx_nic *efx)
@@ -595,9 +580,9 @@ static void efx_remove_channel(struct efx_channel *channel)
         efx_remove_eventq(channel);
 }
 
-void efx_schedule_slow_fill(struct efx_rx_queue *rx_queue, int delay)
+void efx_schedule_slow_fill(struct efx_rx_queue *rx_queue)
 {
-        queue_delayed_work(refill_workqueue, &rx_queue->work, delay);
+        mod_timer(&rx_queue->slow_fill, jiffies + msecs_to_jiffies(100));
 }
 
 /**************************************************************************
@@ -1242,15 +1227,8 @@ static void efx_start_all(struct efx_nic *efx)
  * since we're holding the rtnl_lock at this point. */
 static void efx_flush_all(struct efx_nic *efx)
 {
-        struct efx_rx_queue *rx_queue;
-
         /* Make sure the hardware monitor is stopped */
         cancel_delayed_work_sync(&efx->monitor_work);
-
-        /* Ensure that all RX slow refills are complete. */
-        efx_for_each_rx_queue(rx_queue, efx)
-                cancel_delayed_work_sync(&rx_queue->work);
-
         /* Stop scheduled port reconfigurations */
         cancel_work_sync(&efx->mac_work);
 }
@@ -2064,8 +2042,8 @@ static int efx_init_struct(struct efx_nic *efx, struct efx_nic_type *type,
                 rx_queue->queue = i;
                 rx_queue->channel = &efx->channel[0]; /* for safety */
                 rx_queue->buffer = NULL;
-                spin_lock_init(&rx_queue->add_lock);
-                INIT_DELAYED_WORK(&rx_queue->work, efx_rx_work);
+                setup_timer(&rx_queue->slow_fill, efx_rx_slow_fill,
+                            (unsigned long)rx_queue);
         }
 
         efx->type = type;
@@ -2436,11 +2414,6 @@ static int __init efx_init_module(void)
         if (rc)
                 goto err_notifier;
 
-        refill_workqueue = create_workqueue("sfc_refill");
-        if (!refill_workqueue) {
-                rc = -ENOMEM;
-                goto err_refill;
-        }
         reset_workqueue = create_singlethread_workqueue("sfc_reset");
         if (!reset_workqueue) {
                 rc = -ENOMEM;
@@ -2456,8 +2429,6 @@ static int __init efx_init_module(void)
  err_pci:
         destroy_workqueue(reset_workqueue);
  err_reset:
-        destroy_workqueue(refill_workqueue);
- err_refill:
         unregister_netdevice_notifier(&efx_netdev_notifier);
  err_notifier:
         return rc;
@@ -2469,7 +2440,6 @@ static void __exit efx_exit_module(void)
 
         pci_unregister_driver(&efx_pci_driver);
         destroy_workqueue(reset_workqueue);
-        destroy_workqueue(refill_workqueue);
         unregister_netdevice_notifier(&efx_netdev_notifier);
 
 }