enic: use atomic_t instead of spin_lock in busy poll

We use spinlock to access a single flag. We can avoid spin_locks by using
atomic variable and atomic_cmpxchg(). Use atomic_cmpxchg to set the flag
for idle to poll. And a simple atomic_set to unlock (set idle from poll).

In napi poll, if gro is enabled, we call napi_gro_receive() to deliver the
packets. Before we call napi_complete(), i.e while re-polling, if low
latency busy poll is called, we use netif_receive_skb() to deliver the packets.
At this point if there are some skb's held in GRO, busy poll could deliver the
packets out of order. So we call napi_gro_flush() to flush skbs before we
move the napi poll to idle.

Signed-off-by: Govindarajulu Varadarajan <_govind@gmx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/cisco/enic/enic_main.c b/drivers/net/ethernet/cisco/enic/enic_main.c
index eadae1b..da2004e 100644 (file)
--- a/drivers/net/ethernet/cisco/enic/enic_main.c
+++ b/drivers/net/ethernet/cisco/enic/enic_main.c
@@ -1208,7 +1208,7 @@ static int enic_poll(struct napi_struct *napi, int budget)
                napi_complete(napi);
                vnic_intr_unmask(&enic->intr[intr]);
        }
-       enic_poll_unlock_napi(&enic->rq[cq_rq]);
+       enic_poll_unlock_napi(&enic->rq[cq_rq], napi);
 
        return rq_work_done;
 }
@@ -1414,7 +1414,7 @@ static int enic_poll_msix_rq(struct napi_struct *napi, int budget)
                 */
                enic_calc_int_moderation(enic, &enic->rq[rq]);
 
-       enic_poll_unlock_napi(&enic->rq[rq]);
+       enic_poll_unlock_napi(&enic->rq[rq], napi);
        if (work_done < work_to_do) {
 
                /* Some work done, but not enough to stay in polling,

diff --git a/drivers/net/ethernet/cisco/enic/vnic_rq.h b/drivers/net/ethernet/cisco/enic/vnic_rq.h
index 8111d52..b9c82f1 100644 (file)
--- a/drivers/net/ethernet/cisco/enic/vnic_rq.h
+++ b/drivers/net/ethernet/cisco/enic/vnic_rq.h
@@ -21,6 +21,7 @@
 #define _VNIC_RQ_H_
 
 #include <linux/pci.h>
+#include <linux/netdevice.h>
 
 #include "vnic_dev.h"
 #include "vnic_cq.h"
@@ -75,6 +76,12 @@ struct vnic_rq_buf {
        uint64_t wr_id;
 };
 
+enum enic_poll_state {
+       ENIC_POLL_STATE_IDLE,
+       ENIC_POLL_STATE_NAPI,
+       ENIC_POLL_STATE_POLL
+};
+
 struct vnic_rq {
        unsigned int index;
        struct vnic_dev *vdev;
@@ -86,19 +93,7 @@ struct vnic_rq {
        void *os_buf_head;
        unsigned int pkts_outstanding;
 #ifdef CONFIG_NET_RX_BUSY_POLL
-#define ENIC_POLL_STATE_IDLE           0
-#define ENIC_POLL_STATE_NAPI           (1 << 0) /* NAPI owns this poll */
-#define ENIC_POLL_STATE_POLL           (1 << 1) /* poll owns this poll */
-#define ENIC_POLL_STATE_NAPI_YIELD     (1 << 2) /* NAPI yielded this poll */
-#define ENIC_POLL_STATE_POLL_YIELD     (1 << 3) /* poll yielded this poll */
-#define ENIC_POLL_YIELD                        (ENIC_POLL_STATE_NAPI_YIELD |   \
-                                        ENIC_POLL_STATE_POLL_YIELD)
-#define ENIC_POLL_LOCKED               (ENIC_POLL_STATE_NAPI |         \
-                                        ENIC_POLL_STATE_POLL)
-#define ENIC_POLL_USER_PEND            (ENIC_POLL_STATE_POLL |         \
-                                        ENIC_POLL_STATE_POLL_YIELD)
-       unsigned int bpoll_state;
-       spinlock_t bpoll_lock;
+       atomic_t bpoll_state;
 #endif /* CONFIG_NET_RX_BUSY_POLL */
 };
 
@@ -215,76 +210,43 @@ static inline int vnic_rq_fill(struct vnic_rq *rq,
 #ifdef CONFIG_NET_RX_BUSY_POLL
 static inline void enic_busy_poll_init_lock(struct vnic_rq *rq)
 {
-       spin_lock_init(&rq->bpoll_lock);
-       rq->bpoll_state = ENIC_POLL_STATE_IDLE;
+       atomic_set(&rq->bpoll_state, ENIC_POLL_STATE_IDLE);
 }
 
 static inline bool enic_poll_lock_napi(struct vnic_rq *rq)
 {
-       bool rc = true;
-
-       spin_lock(&rq->bpoll_lock);
-       if (rq->bpoll_state & ENIC_POLL_LOCKED) {
-               WARN_ON(rq->bpoll_state & ENIC_POLL_STATE_NAPI);
-               rq->bpoll_state |= ENIC_POLL_STATE_NAPI_YIELD;
-               rc = false;
-       } else {
-               rq->bpoll_state = ENIC_POLL_STATE_NAPI;
-       }
-       spin_unlock(&rq->bpoll_lock);
+       int rc = atomic_cmpxchg(&rq->bpoll_state, ENIC_POLL_STATE_IDLE,
+                               ENIC_POLL_STATE_NAPI);
 
-       return rc;
+       return (rc == ENIC_POLL_STATE_IDLE);
 }
 
-static inline bool enic_poll_unlock_napi(struct vnic_rq *rq)
+static inline void enic_poll_unlock_napi(struct vnic_rq *rq,
+                                        struct napi_struct *napi)
 {
-       bool rc = false;
-
-       spin_lock(&rq->bpoll_lock);
-       WARN_ON(rq->bpoll_state &
-               (ENIC_POLL_STATE_POLL | ENIC_POLL_STATE_NAPI_YIELD));
-       if (rq->bpoll_state & ENIC_POLL_STATE_POLL_YIELD)
-               rc = true;
-       rq->bpoll_state = ENIC_POLL_STATE_IDLE;
-       spin_unlock(&rq->bpoll_lock);
-
-       return rc;
+       WARN_ON(atomic_read(&rq->bpoll_state) != ENIC_POLL_STATE_NAPI);
+       napi_gro_flush(napi, false);
+       atomic_set(&rq->bpoll_state, ENIC_POLL_STATE_IDLE);
 }
 
 static inline bool enic_poll_lock_poll(struct vnic_rq *rq)
 {
-       bool rc = true;
-
-       spin_lock_bh(&rq->bpoll_lock);
-       if (rq->bpoll_state & ENIC_POLL_LOCKED) {
-               rq->bpoll_state |= ENIC_POLL_STATE_POLL_YIELD;
-               rc = false;
-       } else {
-               rq->bpoll_state |= ENIC_POLL_STATE_POLL;
-       }
-       spin_unlock_bh(&rq->bpoll_lock);
+       int rc = atomic_cmpxchg(&rq->bpoll_state, ENIC_POLL_STATE_IDLE,
+                               ENIC_POLL_STATE_POLL);
 
-       return rc;
+       return (rc == ENIC_POLL_STATE_IDLE);
 }
 
-static inline bool enic_poll_unlock_poll(struct vnic_rq *rq)
-{
-       bool rc = false;
 
-       spin_lock_bh(&rq->bpoll_lock);
-       WARN_ON(rq->bpoll_state & ENIC_POLL_STATE_NAPI);
-       if (rq->bpoll_state & ENIC_POLL_STATE_POLL_YIELD)
-               rc = true;
-       rq->bpoll_state = ENIC_POLL_STATE_IDLE;
-       spin_unlock_bh(&rq->bpoll_lock);
-
-       return rc;
+static inline void enic_poll_unlock_poll(struct vnic_rq *rq)
+{
+       WARN_ON(atomic_read(&rq->bpoll_state) != ENIC_POLL_STATE_POLL);
+       atomic_set(&rq->bpoll_state, ENIC_POLL_STATE_IDLE);
 }
 
 static inline bool enic_poll_busy_polling(struct vnic_rq *rq)
 {
-       WARN_ON(!(rq->bpoll_state & ENIC_POLL_LOCKED));
-       return rq->bpoll_state & ENIC_POLL_USER_PEND;
+       return atomic_read(&rq->bpoll_state) & ENIC_POLL_STATE_POLL;
 }
 
 #else
@@ -298,7 +260,8 @@ static inline bool enic_poll_lock_napi(struct vnic_rq *rq)
        return true;
 }
 
-static inline bool enic_poll_unlock_napi(struct vnic_rq *rq)
+static inline bool enic_poll_unlock_napi(struct vnic_rq *rq,
+                                        struct napi_struct *napi)
 {
        return false;
 }