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xdp: Use nested-BH locking for system_page_pool

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system_page_pool 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.

Make a struct with a page_pool member (original system_page_pool) and a
local_lock_t 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: Andrew Lunn <andrew+netdev@lunn.ch>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jesper Dangaard Brouer <hawk@kernel.org>
Cc: John Fastabend <john.fastabend@gmail.com>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://patch.msgid.link/20250512092736.229935-6-bigeasy@linutronix.de
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Sebastian Andrzej Siewior
2025-05-12 11:27:26 +02:00
committed by Paolo Abeni
parent bc57eda646
commit b9eef3391d
3 changed files with 26 additions and 11 deletions
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15
net/core/dev.c
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@@ -462,7 +462,9 @@ EXPORT_PER_CPU_SYMBOL(softnet_data);
* PP consumers must pay attention to run APIs in the appropriate context
* (e.g. NAPI context).
*/
DEFINE_PER_CPU(struct page_pool *, system_page_pool);
DEFINE_PER_CPU(struct page_pool_bh, system_page_pool) = {
.bh_lock = INIT_LOCAL_LOCK(bh_lock),
};
#ifdef CONFIG_LOCKDEP
/*
@@ -5322,7 +5324,10 @@ netif_skb_check_for_xdp(struct sk_buff **pskb, const struct bpf_prog *prog)
struct sk_buff *skb = *pskb;
int err, hroom, troom;
if (!skb_cow_data_for_xdp(this_cpu_read(system_page_pool), pskb, prog))
local_lock_nested_bh(&system_page_pool.bh_lock);
err = skb_cow_data_for_xdp(this_cpu_read(system_page_pool.pool), pskb, prog);
local_unlock_nested_bh(&system_page_pool.bh_lock);
if (!err)
return 0;
/* In case we have to go down the path and also linearize,
@@ -12712,7 +12717,7 @@ static int net_page_pool_create(int cpuid)
return err;
}
per_cpu(system_page_pool, cpuid) = pp_ptr;
per_cpu(system_page_pool.pool, cpuid) = pp_ptr;
#endif
return 0;
}
@@ -12842,13 +12847,13 @@ out:
for_each_possible_cpu(i) {
struct page_pool *pp_ptr;
pp_ptr = per_cpu(system_page_pool, i);
pp_ptr = per_cpu(system_page_pool.pool, i);
if (!pp_ptr)
continue;
xdp_unreg_page_pool(pp_ptr);
page_pool_destroy(pp_ptr);
per_cpu(system_page_pool, i) = NULL;
per_cpu(system_page_pool.pool, i) = NULL;
}
}