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From: Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 12 Jul 2011 15:38:34 +0200
Subject: net: Use skbufhead with raw lock
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.9/older/patches-4.9.20-rt16.tar.xz
Use the rps lock as rawlock so we can keep irq-off regions. It looks low
latency. However we can't kfree() from this context therefore we defer this
to the softirq and use the tofree_queue list for it (similar to process_queue).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
include/linux/netdevice.h | 1 +
include/linux/skbuff.h | 7 +++++++
net/core/dev.c | 31 ++++++++++++++++++++++++-------
3 files changed, 32 insertions(+), 7 deletions(-)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2855,6 +2855,7 @@ struct softnet_data {
unsigned int dropped;
struct sk_buff_head input_pkt_queue;
struct napi_struct backlog;
+ struct sk_buff_head tofree_queue;
};
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -284,6 +284,7 @@ struct sk_buff_head {
__u32 qlen;
spinlock_t lock;
+ raw_spinlock_t raw_lock;
};
struct sk_buff;
@@ -1573,6 +1574,12 @@ static inline void skb_queue_head_init(s
__skb_queue_head_init(list);
}
+static inline void skb_queue_head_init_raw(struct sk_buff_head *list)
+{
+ raw_spin_lock_init(&list->raw_lock);
+ __skb_queue_head_init(list);
+}
+
static inline void skb_queue_head_init_class(struct sk_buff_head *list,
struct lock_class_key *class)
{
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -211,14 +211,14 @@ static inline struct hlist_head *dev_ind
static inline void rps_lock(struct softnet_data *sd)
{
#ifdef CONFIG_RPS
- spin_lock(&sd->input_pkt_queue.lock);
+ raw_spin_lock(&sd->input_pkt_queue.raw_lock);
#endif
}
static inline void rps_unlock(struct softnet_data *sd)
{
#ifdef CONFIG_RPS
- spin_unlock(&sd->input_pkt_queue.lock);
+ raw_spin_unlock(&sd->input_pkt_queue.raw_lock);
#endif
}
@@ -4337,7 +4337,7 @@ static void flush_backlog(struct work_st
skb_queue_walk_safe(&sd->input_pkt_queue, skb, tmp) {
if (skb->dev->reg_state == NETREG_UNREGISTERING) {
__skb_unlink(skb, &sd->input_pkt_queue);
- kfree_skb(skb);
+ __skb_queue_tail(&sd->tofree_queue, skb);
input_queue_head_incr(sd);
}
}
@@ -4347,11 +4347,14 @@ static void flush_backlog(struct work_st
skb_queue_walk_safe(&sd->process_queue, skb, tmp) {
if (skb->dev->reg_state == NETREG_UNREGISTERING) {
__skb_unlink(skb, &sd->process_queue);
- kfree_skb(skb);
+ __skb_queue_tail(&sd->tofree_queue, skb);
input_queue_head_incr(sd);
}
}
+ if (!skb_queue_empty(&sd->tofree_queue))
+ raise_softirq_irqoff(NET_RX_SOFTIRQ);
local_bh_enable();
+
}
static void flush_all_backlogs(void)
@@ -4876,7 +4879,9 @@ static int process_backlog(struct napi_s
while (again) {
struct sk_buff *skb;
+ local_irq_disable();
while ((skb = __skb_dequeue(&sd->process_queue))) {
+ local_irq_enable();
rcu_read_lock();
__netif_receive_skb(skb);
rcu_read_unlock();
@@ -4884,9 +4889,9 @@ static int process_backlog(struct napi_s
if (++work >= quota)
return work;
+ local_irq_disable();
}
- local_irq_disable();
rps_lock(sd);
if (skb_queue_empty(&sd->input_pkt_queue)) {
/*
@@ -5228,13 +5233,21 @@ static __latent_entropy void net_rx_acti
struct softnet_data *sd = this_cpu_ptr(&softnet_data);
unsigned long time_limit = jiffies + 2;
int budget = netdev_budget;
+ struct sk_buff_head tofree_q;
+ struct sk_buff *skb;
LIST_HEAD(list);
LIST_HEAD(repoll);
+ __skb_queue_head_init(&tofree_q);
+
local_irq_disable();
+ skb_queue_splice_init(&sd->tofree_queue, &tofree_q);
list_splice_init(&sd->poll_list, &list);
local_irq_enable();
+ while ((skb = __skb_dequeue(&tofree_q)))
+ kfree_skb(skb);
+
for (;;) {
struct napi_struct *n;
@@ -8037,6 +8050,9 @@ static int dev_cpu_callback(struct notif
netif_rx_ni(skb);
input_queue_head_incr(oldsd);
}
+ while ((skb = __skb_dequeue(&oldsd->tofree_queue))) {
+ kfree_skb(skb);
+ }
return NOTIFY_OK;
}
@@ -8341,8 +8357,9 @@ static int __init net_dev_init(void)
INIT_WORK(flush, flush_backlog);
- skb_queue_head_init(&sd->input_pkt_queue);
- skb_queue_head_init(&sd->process_queue);
+ skb_queue_head_init_raw(&sd->input_pkt_queue);
+ skb_queue_head_init_raw(&sd->process_queue);
+ skb_queue_head_init_raw(&sd->tofree_queue);
INIT_LIST_HEAD(&sd->poll_list);
sd->output_queue_tailp = &sd->output_queue;
#ifdef CONFIG_RPS
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