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net/sched: act_mirred: Move the recursion counter struct netdev_xmit

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mirred_nest_level is a per-CPU variable and relies on disabled BH for its
locking. Without per-CPU locking in local_bh_disable() on PREEMPT_RT
this data structure requires explicit locking.

Move mirred_nest_level to struct netdev_xmit as u8, provide wrappers.

Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://patch.msgid.link/20250512092736.229935-11-bigeasy@linutronix.de
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Sebastian Andrzej Siewior 2025-05-12 11:27:31 +02:00 committed by Paolo Abeni
parent 3af4cdd67f
commit 7fe70c06a1
2 changed files with 28 additions and 3 deletions
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3
include/linux/netdevice_xmit.h
View File

@ -8,6 +8,9 @@ struct netdev_xmit {
#ifdef CONFIG_NET_EGRESS
u8 skip_txqueue;
#endif
#if IS_ENABLED(CONFIG_NET_ACT_MIRRED)
u8 sched_mirred_nest;
#endif
};
#endif

28
net/sched/act_mirred.c
View File

@ -30,7 +30,29 @@ static LIST_HEAD(mirred_list);
static DEFINE_SPINLOCK(mirred_list_lock);
#define MIRRED_NEST_LIMIT 4
static DEFINE_PER_CPU(unsigned int, mirred_nest_level);
#ifndef CONFIG_PREEMPT_RT
static u8 tcf_mirred_nest_level_inc_return(void)
{
return __this_cpu_inc_return(softnet_data.xmit.sched_mirred_nest);
}
static void tcf_mirred_nest_level_dec(void)
{
__this_cpu_dec(softnet_data.xmit.sched_mirred_nest);
}
#else
static u8 tcf_mirred_nest_level_inc_return(void)
{
return current->net_xmit.sched_mirred_nest++;
}
static void tcf_mirred_nest_level_dec(void)
{
current->net_xmit.sched_mirred_nest--;
}
#endif
static bool tcf_mirred_is_act_redirect(int action)
{
@ -423,7 +445,7 @@ TC_INDIRECT_SCOPE int tcf_mirred_act(struct sk_buff *skb,
int m_eaction;
u32 blockid;
nest_level = __this_cpu_inc_return(mirred_nest_level);
nest_level = tcf_mirred_nest_level_inc_return();
if (unlikely(nest_level > MIRRED_NEST_LIMIT)) {
net_warn_ratelimited("Packet exceeded mirred recursion limit on dev %s\n",
netdev_name(skb->dev));
@ -454,7 +476,7 @@ TC_INDIRECT_SCOPE int tcf_mirred_act(struct sk_buff *skb,
retval);
dec_nest_level:
__this_cpu_dec(mirred_nest_level);
tcf_mirred_nest_level_dec();
return retval;
}