ixgbe: Refactor busy poll socket code to address multiple issues

This change addresses several issues in the current ixgbe implementation of
busy poll sockets.

First was the fact that it was possible for frames to be delivered out of
order if they were held in GRO.  This is addressed by flushing the GRO buffers
before releasing the q_vector back to the idle state.

The other issue was the fact that we were having to take a spinlock on
changing the state to and from idle.  To resolve this I have replaced the
state value with an atomic and use atomic_cmpxchg to change the value from
idle, and a simple atomic set to restore it back to idle after we have
acquired it.  This allows us to only use a locked operation on acquiring the
vector without a need for a locked operation to release it.
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/ixgbe/ixgbe.h

@@ -386,119 +386,87 @@ struct ixgbe_q_vector {
 	char name[IFNAMSIZ + 9];
 
 #ifdef CONFIG_NET_RX_BUSY_POLL
-	unsigned int state;
-#define IXGBE_QV_STATE_IDLE        0
-#define IXGBE_QV_STATE_NAPI	   1     /* NAPI owns this QV */
-#define IXGBE_QV_STATE_POLL	   2     /* poll owns this QV */
-#define IXGBE_QV_STATE_DISABLED	   4     /* QV is disabled */
-#define IXGBE_QV_OWNED (IXGBE_QV_STATE_NAPI | IXGBE_QV_STATE_POLL)
-#define IXGBE_QV_LOCKED (IXGBE_QV_OWNED | IXGBE_QV_STATE_DISABLED)
-#define IXGBE_QV_STATE_NAPI_YIELD  8     /* NAPI yielded this QV */
-#define IXGBE_QV_STATE_POLL_YIELD  16    /* poll yielded this QV */
-#define IXGBE_QV_YIELD (IXGBE_QV_STATE_NAPI_YIELD | IXGBE_QV_STATE_POLL_YIELD)
-#define IXGBE_QV_USER_PEND (IXGBE_QV_STATE_POLL | IXGBE_QV_STATE_POLL_YIELD)
-	spinlock_t lock;
+	atomic_t state;
 #endif  /* CONFIG_NET_RX_BUSY_POLL */
 
 	/* for dynamic allocation of rings associated with this q_vector */
 	struct ixgbe_ring ring[0] ____cacheline_internodealigned_in_smp;
 };
+
 #ifdef CONFIG_NET_RX_BUSY_POLL
+enum ixgbe_qv_state_t {
+	IXGBE_QV_STATE_IDLE = 0,
+	IXGBE_QV_STATE_NAPI,
+	IXGBE_QV_STATE_POLL,
+	IXGBE_QV_STATE_DISABLE
+};
+
 static inline void ixgbe_qv_init_lock(struct ixgbe_q_vector *q_vector)
 {
-
-	spin_lock_init(&q_vector->lock);
-	q_vector->state = IXGBE_QV_STATE_IDLE;
+	/* reset state to idle */
+	atomic_set(&q_vector->state, IXGBE_QV_STATE_IDLE);
 }
 
 /* called from the device poll routine to get ownership of a q_vector */
 static inline bool ixgbe_qv_lock_napi(struct ixgbe_q_vector *q_vector)
 {
-	int rc = true;
-	spin_lock_bh(&q_vector->lock);
-	if (q_vector->state & IXGBE_QV_LOCKED) {
-		WARN_ON(q_vector->state & IXGBE_QV_STATE_NAPI);
-		q_vector->state |= IXGBE_QV_STATE_NAPI_YIELD;
-		rc = false;
+	int rc = atomic_cmpxchg(&q_vector->state, IXGBE_QV_STATE_IDLE,
+				IXGBE_QV_STATE_NAPI);
 #ifdef BP_EXTENDED_STATS
+	if (rc != IXGBE_QV_STATE_IDLE)
 		q_vector->tx.ring->stats.yields++;
 #endif
-	} else {
-		/* we don't care if someone yielded */
-		q_vector->state = IXGBE_QV_STATE_NAPI;
-	}
-	spin_unlock_bh(&q_vector->lock);
-	return rc;
+
+	return rc == IXGBE_QV_STATE_IDLE;
 }
 
 /* returns true is someone tried to get the qv while napi had it */
-static inline bool ixgbe_qv_unlock_napi(struct ixgbe_q_vector *q_vector)
+static inline void ixgbe_qv_unlock_napi(struct ixgbe_q_vector *q_vector)
 {
-	int rc = false;
-	spin_lock_bh(&q_vector->lock);
-	WARN_ON(q_vector->state & (IXGBE_QV_STATE_POLL |
-			       IXGBE_QV_STATE_NAPI_YIELD));
-
-	if (q_vector->state & IXGBE_QV_STATE_POLL_YIELD)
-		rc = true;
-	/* will reset state to idle, unless QV is disabled */
-	q_vector->state &= IXGBE_QV_STATE_DISABLED;
-	spin_unlock_bh(&q_vector->lock);
-	return rc;
+	WARN_ON(atomic_read(&q_vector->state) != IXGBE_QV_STATE_NAPI);
+
+	/* flush any outstanding Rx frames */
+	if (q_vector->napi.gro_list)
+		napi_gro_flush(&q_vector->napi, false);
+
+	/* reset state to idle */
+	atomic_set(&q_vector->state, IXGBE_QV_STATE_IDLE);
 }
 
 /* called from ixgbe_low_latency_poll() */
 static inline bool ixgbe_qv_lock_poll(struct ixgbe_q_vector *q_vector)
 {
-	int rc = true;
-	spin_lock_bh(&q_vector->lock);
-	if ((q_vector->state & IXGBE_QV_LOCKED)) {
-		q_vector->state |= IXGBE_QV_STATE_POLL_YIELD;
-		rc = false;
+	int rc = atomic_cmpxchg(&q_vector->state, IXGBE_QV_STATE_IDLE,
+				IXGBE_QV_STATE_POLL);
 #ifdef BP_EXTENDED_STATS
-		q_vector->rx.ring->stats.yields++;
+	if (rc != IXGBE_QV_STATE_IDLE)
+		q_vector->tx.ring->stats.yields++;
 #endif
-	} else {
-		/* preserve yield marks */
-		q_vector->state |= IXGBE_QV_STATE_POLL;
-	}
-	spin_unlock_bh(&q_vector->lock);
-	return rc;
+	return rc == IXGBE_QV_STATE_IDLE;
 }
 
 /* returns true if someone tried to get the qv while it was locked */
-static inline bool ixgbe_qv_unlock_poll(struct ixgbe_q_vector *q_vector)
+static inline void ixgbe_qv_unlock_poll(struct ixgbe_q_vector *q_vector)
 {
-	int rc = false;
-	spin_lock_bh(&q_vector->lock);
-	WARN_ON(q_vector->state & (IXGBE_QV_STATE_NAPI));
-
-	if (q_vector->state & IXGBE_QV_STATE_POLL_YIELD)
-		rc = true;
-	/* will reset state to idle, unless QV is disabled */
-	q_vector->state &= IXGBE_QV_STATE_DISABLED;
-	spin_unlock_bh(&q_vector->lock);
-	return rc;
+	WARN_ON(atomic_read(&q_vector->state) != IXGBE_QV_STATE_POLL);
+
+	/* reset state to idle */
+	atomic_set(&q_vector->state, IXGBE_QV_STATE_IDLE);
 }
 
 /* true if a socket is polling, even if it did not get the lock */
 static inline bool ixgbe_qv_busy_polling(struct ixgbe_q_vector *q_vector)
 {
-	WARN_ON(!(q_vector->state & IXGBE_QV_OWNED));
-	return q_vector->state & IXGBE_QV_USER_PEND;
+	return atomic_read(&q_vector->state) == IXGBE_QV_STATE_POLL;
 }
 
 /* false if QV is currently owned */
 static inline bool ixgbe_qv_disable(struct ixgbe_q_vector *q_vector)
 {
-	int rc = true;
-	spin_lock_bh(&q_vector->lock);
-	if (q_vector->state & IXGBE_QV_OWNED)
-		rc = false;
-	q_vector->state |= IXGBE_QV_STATE_DISABLED;
-	spin_unlock_bh(&q_vector->lock);
-
-	return rc;
+	int rc = atomic_cmpxchg(&q_vector->state, IXGBE_QV_STATE_IDLE,
+				IXGBE_QV_STATE_DISABLE);
+
+	return rc == IXGBE_QV_STATE_IDLE;
 }
 
 #else /* CONFIG_NET_RX_BUSY_POLL */

drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c

@@ -807,6 +807,11 @@ static int ixgbe_alloc_q_vector(struct ixgbe_adapter *adapter,
 		       ixgbe_poll, 64);
 	napi_hash_add(&q_vector->napi);
 
+#ifdef CONFIG_NET_RX_BUSY_POLL
+	/* initialize busy poll */
+	atomic_set(&q_vector->state, IXGBE_QV_STATE_DISABLE);
+
+#endif
 	/* tie q_vector and adapter together */
 	adapter->q_vector[v_idx] = q_vector;
 	q_vector->adapter = adapter;