[PATCH net-next 14/18] net/sched: Use nested-BH locking for sch_frag_data_storage.
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: 2025-03-09 14:47:13
Also in:
linux-rt-devel
Subsystem:
networking [general], tc subsystem, the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Jamal Hadi Salim, Jiri Pirko, Linus Torvalds
sch_frag_data_storage 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. Add local_lock_t to the struct and use local_lock_nested_bh() for locking. This change adds only lockdep coverage and does not alter the functional behaviour for !PREEMPT_RT. Cc: Jamal Hadi Salim <jhs@mojatatu.com> Cc: Cong Wang <redacted> Cc: Jiri Pirko <jiri@resnulli.us> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- net/sched/sch_frag.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/net/sched/sch_frag.c b/net/sched/sch_frag.c
index ce63414185fd6..d1d87dce7f3f7 100644
--- a/net/sched/sch_frag.c
+++ b/net/sched/sch_frag.c@@ -16,14 +16,18 @@ struct sch_frag_data { unsigned int l2_len; u8 l2_data[VLAN_ETH_HLEN]; int (*xmit)(struct sk_buff *skb); + local_lock_t bh_lock; }; -static DEFINE_PER_CPU(struct sch_frag_data, sch_frag_data_storage); +static DEFINE_PER_CPU(struct sch_frag_data, sch_frag_data_storage) = { + .bh_lock = INIT_LOCAL_LOCK(bh_lock), +}; static int sch_frag_xmit(struct net *net, struct sock *sk, struct sk_buff *skb) { struct sch_frag_data *data = this_cpu_ptr(&sch_frag_data_storage); + lockdep_assert_held(&data->bh_lock); if (skb_cow_head(skb, data->l2_len) < 0) { kfree_skb(skb); return -ENOMEM;
@@ -95,6 +99,7 @@ static int sch_fragment(struct net *net, struct sk_buff *skb, struct rtable sch_frag_rt = { 0 }; unsigned long orig_dst; + local_lock_nested_bh(&sch_frag_data_storage.bh_lock); sch_frag_prepare_frag(skb, xmit); dst_init(&sch_frag_rt.dst, &sch_frag_dst_ops, NULL, DST_OBSOLETE_NONE, DST_NOCOUNT);
@@ -105,11 +110,13 @@ static int sch_fragment(struct net *net, struct sk_buff *skb, IPCB(skb)->frag_max_size = mru; ret = ip_do_fragment(net, skb->sk, skb, sch_frag_xmit); + local_unlock_nested_bh(&sch_frag_data_storage.bh_lock); refdst_drop(orig_dst); } else if (skb_protocol(skb, true) == htons(ETH_P_IPV6)) { unsigned long orig_dst; struct rt6_info sch_frag_rt; + local_lock_nested_bh(&sch_frag_data_storage.bh_lock); sch_frag_prepare_frag(skb, xmit); memset(&sch_frag_rt, 0, sizeof(sch_frag_rt)); dst_init(&sch_frag_rt.dst, &sch_frag_dst_ops, NULL,
@@ -122,6 +129,7 @@ static int sch_fragment(struct net *net, struct sk_buff *skb, ret = ipv6_stub->ipv6_fragment(net, skb->sk, skb, sch_frag_xmit); + local_unlock_nested_bh(&sch_frag_data_storage.bh_lock); refdst_drop(orig_dst); } else { net_warn_ratelimited("Fail frag %s: eth=%x, MRU=%d, MTU=%d\n",
--
2.47.2