From 1f6394e382f137f07136182c591ca8a7eeba6a06 Mon Sep 17 00:00:00 2001 From: Sowmini Varadhan Date: Tue, 12 Aug 2014 10:27:24 -0400 Subject: sunvnet: Do not ask for an ACK for every dring transmit No need to ask for an ack with every vnet_start_xmit()- the single ACK with DRING_STOPPED is sufficient for the protocol, and we free the sk_buff in vnet_start_xmit itself, so we dont need an ACK back. Signed-off-by: Sowmini Varadhan Acked-by: Raghuram Kothakota Signed-off-by: David S. Miller --- drivers/net/ethernet/sun/sunvnet.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) (limited to 'drivers/net/ethernet/sun/sunvnet.c') diff --git a/drivers/net/ethernet/sun/sunvnet.c b/drivers/net/ethernet/sun/sunvnet.c index d813bfb1a84..238434dcfe0 100644 --- a/drivers/net/ethernet/sun/sunvnet.c +++ b/drivers/net/ethernet/sun/sunvnet.c @@ -691,7 +691,15 @@ static int vnet_start_xmit(struct sk_buff *skb, struct net_device *dev) memset(tx_buf+VNET_PACKET_SKIP+skb->len, 0, len - skb->len); } - d->hdr.ack = VIO_ACK_ENABLE; + /* We don't rely on the ACKs to free the skb in vnet_start_xmit(), + * thus it is safe to not set VIO_ACK_ENABLE for each transmission: + * the protocol itself does not require it as long as the peer + * sends a VIO_SUBTYPE_ACK for VIO_DRING_STOPPED. + * + * An ACK for every packet in the ring is expensive as the + * sending of LDC messages is slow and affects performance. + */ + d->hdr.ack = VIO_ACK_DISABLE; d->size = len; d->ncookies = port->tx_bufs[dr->prod].ncookies; for (i = 0; i < d->ncookies; i++) -- cgit v1.2.3-70-g09d2 From adddc32d6fde82156c779997f928865100542e55 Mon Sep 17 00:00:00 2001 From: Sowmini Varadhan Date: Tue, 12 Aug 2014 10:33:10 -0400 Subject: sunvnet: Do not spin in an infinite loop when vio_ldc_send() returns EAGAIN ldc_rx -> vnet_rx -> .. -> vnet_walk_rx->vnet_send_ack should not spin into an infinite loop waiting EAGAIN to lift. The sender could have sent us a burst, and gone to lunch without doing any more ldc_read()'s. That should not cause the receiver to loop infinitely till soft-lockup kicks in. Similarly __vnet_tx_trigger should only loop on EAGAIN a finite number of times. The caller (vnet_start_xmit()) already has code to reset the dring state and bail on errors from __vnet_tx_trigger Signed-off-by: Sowmini Varadhan Acked-by: Raghuram Kothakota Signed-off-by: David S. Miller --- drivers/net/ethernet/sun/sunvnet.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) (limited to 'drivers/net/ethernet/sun/sunvnet.c') diff --git a/drivers/net/ethernet/sun/sunvnet.c b/drivers/net/ethernet/sun/sunvnet.c index 238434dcfe0..a5871791e45 100644 --- a/drivers/net/ethernet/sun/sunvnet.c +++ b/drivers/net/ethernet/sun/sunvnet.c @@ -32,6 +32,11 @@ MODULE_DESCRIPTION("Sun LDOM virtual network driver"); MODULE_LICENSE("GPL"); MODULE_VERSION(DRV_MODULE_VERSION); +/* Heuristic for the number of times to exponentially backoff and + * retry sending an LDC trigger when EAGAIN is encountered + */ +#define VNET_MAX_RETRIES 10 + /* Ordered from largest major to lowest */ static struct vio_version vnet_versions[] = { { .major = 1, .minor = 0 }, @@ -260,6 +265,7 @@ static int vnet_send_ack(struct vnet_port *port, struct vio_dring_state *dr, .state = vio_dring_state, }; int err, delay; + int retries = 0; hdr.seq = dr->snd_nxt; delay = 1; @@ -272,6 +278,13 @@ static int vnet_send_ack(struct vnet_port *port, struct vio_dring_state *dr, udelay(delay); if ((delay <<= 1) > 128) delay = 128; + if (retries++ > VNET_MAX_RETRIES) { + pr_info("ECONNRESET %x:%x:%x:%x:%x:%x\n", + port->raddr[0], port->raddr[1], + port->raddr[2], port->raddr[3], + port->raddr[4], port->raddr[5]); + err = -ECONNRESET; + } } while (err == -EAGAIN); return err; @@ -593,6 +606,7 @@ static int __vnet_tx_trigger(struct vnet_port *port) .end_idx = (u32) -1, }; int err, delay; + int retries = 0; hdr.seq = dr->snd_nxt; delay = 1; @@ -605,6 +619,8 @@ static int __vnet_tx_trigger(struct vnet_port *port) udelay(delay); if ((delay <<= 1) > 128) delay = 128; + if (retries++ > VNET_MAX_RETRIES) + break; } while (err == -EAGAIN); return err; -- cgit v1.2.3-70-g09d2 From 1d311ad2f9fe5d75cf228372174170d0f435e3ef Mon Sep 17 00:00:00 2001 From: Sowmini Varadhan Date: Wed, 13 Aug 2014 10:29:41 -0400 Subject: sunvnet: Schedule maybe_tx_wakeup() as a tasklet from ldc_rx path At the tail of vnet_event(), if we hit the maybe_tx_wakeup() condition, we try to take the netif_tx_lock() in the recv-interrupt-context and can deadlock with dev_watchdog(). vnet_event() should schedule maybe_tx_wakeup() as a tasklet to avoid this deadlock Signed-off-by: Sowmini Varadhan Signed-off-by: David S. Miller --- drivers/net/ethernet/sun/sunvnet.c | 12 ++++++++++-- drivers/net/ethernet/sun/sunvnet.h | 4 ++++ 2 files changed, 14 insertions(+), 2 deletions(-) (limited to 'drivers/net/ethernet/sun/sunvnet.c') diff --git a/drivers/net/ethernet/sun/sunvnet.c b/drivers/net/ethernet/sun/sunvnet.c index a5871791e45..23c89ab5a6a 100644 --- a/drivers/net/ethernet/sun/sunvnet.c +++ b/drivers/net/ethernet/sun/sunvnet.c @@ -488,8 +488,9 @@ static int handle_mcast(struct vnet_port *port, void *msgbuf) return 0; } -static void maybe_tx_wakeup(struct vnet *vp) +static void maybe_tx_wakeup(unsigned long param) { + struct vnet *vp = (struct vnet *)param; struct net_device *dev = vp->dev; netif_tx_lock(dev); @@ -586,8 +587,13 @@ static void vnet_event(void *arg, int event) break; } spin_unlock(&vio->lock); + /* Kick off a tasklet to wake the queue. We cannot call + * maybe_tx_wakeup directly here because we could deadlock on + * netif_tx_lock() with dev_watchdog() + */ if (unlikely(tx_wakeup && err != -ECONNRESET)) - maybe_tx_wakeup(port->vp); + tasklet_schedule(&port->vp->vnet_tx_wakeup); + local_irq_restore(flags); } @@ -1070,6 +1076,7 @@ static struct vnet *vnet_new(const u64 *local_mac) vp = netdev_priv(dev); spin_lock_init(&vp->lock); + tasklet_init(&vp->vnet_tx_wakeup, maybe_tx_wakeup, (unsigned long)vp); vp->dev = dev; INIT_LIST_HEAD(&vp->port_list); @@ -1129,6 +1136,7 @@ static void vnet_cleanup(void) vp = list_first_entry(&vnet_list, struct vnet, list); list_del(&vp->list); dev = vp->dev; + tasklet_kill(&vp->vnet_tx_wakeup); /* vio_unregister_driver() should have cleaned up port_list */ BUG_ON(!list_empty(&vp->port_list)); unregister_netdev(dev); diff --git a/drivers/net/ethernet/sun/sunvnet.h b/drivers/net/ethernet/sun/sunvnet.h index d347a5bf24b..de5c2c64996 100644 --- a/drivers/net/ethernet/sun/sunvnet.h +++ b/drivers/net/ethernet/sun/sunvnet.h @@ -1,6 +1,8 @@ #ifndef _SUNVNET_H #define _SUNVNET_H +#include + #define DESC_NCOOKIES(entry_size) \ ((entry_size) - sizeof(struct vio_net_desc)) @@ -78,6 +80,8 @@ struct vnet { struct list_head list; u64 local_mac; + + struct tasklet_struct vnet_tx_wakeup; }; #endif /* _SUNVNET_H */ -- cgit v1.2.3-70-g09d2