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net: remove NETDEV_TX_LOCKED support

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No more users in the tree, remove NETDEV_TX_LOCKED support.
Adds another hole in softnet_stats struct, but better than keeping
the unused collision counter around.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Florian Westphal 2016-04-24 21:38:14 +02:00 committed by David S. Miller
parent a6086a8937
commit f0cdf76c10
6 changed files with 9 additions and 49 deletions
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10
Documentation/networking/netdev-features.txt
View File

@ -131,13 +131,11 @@ stack. Driver should not change behaviour based on them.
* LLTX driver (deprecated for hardware drivers)
NETIF_F_LLTX should be set in drivers that implement their own locking in
transmit path or don't need locking at all (e.g. software tunnels).
In ndo_start_xmit, it is recommended to use a try_lock and return
NETDEV_TX_LOCKED when the spin lock fails. The locking should also properly
protect against other callbacks (the rules you need to find out).
NETIF_F_LLTX is meant to be used by drivers that don't need locking at all,
e.g. software tunnels.
Don't use it for new drivers.
This is also used in a few legacy drivers that implement their
own locking, don't use it for new (hardware) drivers.
* netns-local device

9
Documentation/networking/netdevices.txt
View File

@ -69,10 +69,9 @@ ndo_start_xmit:
When the driver sets NETIF_F_LLTX in dev->features this will be
called without holding netif_tx_lock. In this case the driver
has to lock by itself when needed. It is recommended to use a try lock
for this and return NETDEV_TX_LOCKED when the spin lock fails.
The locking there should also properly protect against
set_rx_mode. Note that the use of NETIF_F_LLTX is deprecated.
has to lock by itself when needed.
The locking there should also properly protect against
set_rx_mode. WARNING: use of NETIF_F_LLTX is deprecated.
Don't use it for new drivers.
Context: Process with BHs disabled or BH (timer),
@ -83,8 +82,6 @@ ndo_start_xmit:
o NETDEV_TX_BUSY Cannot transmit packet, try later
Usually a bug, means queue start/stop flow control is broken in
the driver. Note: the driver must NOT put the skb in its DMA ring.
o NETDEV_TX_LOCKED Locking failed, please retry quickly.
Only valid when NETIF_F_LLTX is set.
ndo_tx_timeout:
Synchronization: netif_tx_lock spinlock; all TX queues frozen.

3
include/linux/netdevice.h
View File

@ -106,7 +106,6 @@ enum netdev_tx {
__NETDEV_TX_MIN = INT_MIN, /* make sure enum is signed */
NETDEV_TX_OK = 0x00, /* driver took care of packet */
NETDEV_TX_BUSY = 0x10, /* driver tx path was busy*/
NETDEV_TX_LOCKED = 0x20, /* driver tx lock was already taken */
};
typedef enum netdev_tx netdev_tx_t;
@ -831,7 +830,6 @@ struct tc_to_netdev {
* the queue before that can happen; it's for obsolete devices and weird
* corner cases, but the stack really does a non-trivial amount
* of useless work if you return NETDEV_TX_BUSY.
* (can also return NETDEV_TX_LOCKED iff NETIF_F_LLTX)
* Required; cannot be NULL.
*
* netdev_features_t (*ndo_fix_features)(struct net_device *dev,
@ -2737,7 +2735,6 @@ struct softnet_data {
/* stats */
unsigned int processed;
unsigned int time_squeeze;
unsigned int cpu_collision;
unsigned int received_rps;
#ifdef CONFIG_RPS
struct softnet_data *rps_ipi_list;

3
net/core/net-procfs.c
View File

@ -162,7 +162,8 @@ static int softnet_seq_show(struct seq_file *seq, void *v)
"%08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x\n",
sd->processed, sd->dropped, sd->time_squeeze, 0,
0, 0, 0, 0, /* was fastroute */
sd->cpu_collision, sd->received_rps, flow_limit_count);
0, /* was cpu_collision */
sd->received_rps, flow_limit_count);
return 0;
}

1
net/core/pktgen.c
View File

@ -3472,7 +3472,6 @@ xmit_more:
pkt_dev->odevname, ret);
pkt_dev->errors++;
/* fallthru */
case NETDEV_TX_LOCKED:
case NETDEV_TX_BUSY:
/* Retry it next time */
atomic_dec(&(pkt_dev->skb->users));

32
net/sched/sch_generic.c
View File

@ -108,35 +108,6 @@ static struct sk_buff *dequeue_skb(struct Qdisc *q, bool *validate,
return skb;
}
static inline int handle_dev_cpu_collision(struct sk_buff *skb,
struct netdev_queue *dev_queue,
struct Qdisc *q)
{
int ret;
if (unlikely(dev_queue->xmit_lock_owner == smp_processor_id())) {
/*
* Same CPU holding the lock. It may be a transient
* configuration error, when hard_start_xmit() recurses. We
* detect it by checking xmit owner and drop the packet when
* deadloop is detected. Return OK to try the next skb.
*/
kfree_skb_list(skb);
net_warn_ratelimited("Dead loop on netdevice %s, fix it urgently!\n",
dev_queue->dev->name);
ret = qdisc_qlen(q);
} else {
/*
* Another cpu is holding lock, requeue & delay xmits for
* some time.
*/
__this_cpu_inc(softnet_data.cpu_collision);
ret = dev_requeue_skb(skb, q);
}
return ret;
}
/*
* Transmit possibly several skbs, and handle the return status as
* required. Holding the __QDISC___STATE_RUNNING bit guarantees that
@ -174,9 +145,6 @@ int sch_direct_xmit(struct sk_buff *skb, struct Qdisc *q,
if (dev_xmit_complete(ret)) {
/* Driver sent out skb successfully or skb was consumed */
ret = qdisc_qlen(q);
} else if (ret == NETDEV_TX_LOCKED) {
/* Driver try lock failed */
ret = handle_dev_cpu_collision(skb, txq, q);
} else {
/* Driver returned NETDEV_TX_BUSY - requeue skb */
if (unlikely(ret != NETDEV_TX_BUSY))