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net: dst_cache: Use nested-BH locking for dst_cache::cache

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dst_cache::cache 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 a local_lock_t to the data structure and use
local_lock_nested_bh() for locking. This change adds only lockdep
coverage and does not alter the functional behaviour for !PREEMPT_RT.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://patch.msgid.link/20250512092736.229935-3-bigeasy@linutronix.de
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Sebastian Andrzej Siewior 2025-05-12 11:27:23 +02:00 committed by Paolo Abeni
parent 32471b2f48
commit c99dac52ff
1 changed files with 27 additions and 3 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

30
net/core/dst_cache.c
View file

@ -17,6 +17,7 @@
struct dst_cache_pcpu {
unsigned long refresh_ts;
struct dst_entry *dst;
local_lock_t bh_lock;
u32 cookie;
union {
struct in_addr in_saddr;
@ -65,10 +66,15 @@ static struct dst_entry *dst_cache_per_cpu_get(struct dst_cache *dst_cache,
struct dst_entry *dst_cache_get(struct dst_cache *dst_cache)
{
struct dst_entry *dst;
if (!dst_cache->cache)
return NULL;
return dst_cache_per_cpu_get(dst_cache, this_cpu_ptr(dst_cache->cache));
local_lock_nested_bh(&dst_cache->cache->bh_lock);
dst = dst_cache_per_cpu_get(dst_cache, this_cpu_ptr(dst_cache->cache));
local_unlock_nested_bh(&dst_cache->cache->bh_lock);
return dst;
}
EXPORT_SYMBOL_GPL(dst_cache_get);
@ -80,12 +86,16 @@ struct rtable *dst_cache_get_ip4(struct dst_cache *dst_cache, __be32 *saddr)
if (!dst_cache->cache)
return NULL;
local_lock_nested_bh(&dst_cache->cache->bh_lock);
idst = this_cpu_ptr(dst_cache->cache);
dst = dst_cache_per_cpu_get(dst_cache, idst);
if (!dst)
if (!dst) {
local_unlock_nested_bh(&dst_cache->cache->bh_lock);
return NULL;
}
*saddr = idst->in_saddr.s_addr;
local_unlock_nested_bh(&dst_cache->cache->bh_lock);
return dst_rtable(dst);
}
EXPORT_SYMBOL_GPL(dst_cache_get_ip4);
@ -98,9 +108,11 @@ void dst_cache_set_ip4(struct dst_cache *dst_cache, struct dst_entry *dst,
if (!dst_cache->cache)
return;
local_lock_nested_bh(&dst_cache->cache->bh_lock);
idst = this_cpu_ptr(dst_cache->cache);
dst_cache_per_cpu_dst_set(idst, dst, 0);
idst->in_saddr.s_addr = saddr;
local_unlock_nested_bh(&dst_cache->cache->bh_lock);
}
EXPORT_SYMBOL_GPL(dst_cache_set_ip4);
@ -113,10 +125,13 @@ void dst_cache_set_ip6(struct dst_cache *dst_cache, struct dst_entry *dst,
if (!dst_cache->cache)
return;
local_lock_nested_bh(&dst_cache->cache->bh_lock);
idst = this_cpu_ptr(dst_cache->cache);
dst_cache_per_cpu_dst_set(idst, dst,
rt6_get_cookie(dst_rt6_info(dst)));
idst->in6_saddr = *saddr;
local_unlock_nested_bh(&dst_cache->cache->bh_lock);
}
EXPORT_SYMBOL_GPL(dst_cache_set_ip6);
@ -129,12 +144,17 @@ struct dst_entry *dst_cache_get_ip6(struct dst_cache *dst_cache,
if (!dst_cache->cache)
return NULL;
local_lock_nested_bh(&dst_cache->cache->bh_lock);
idst = this_cpu_ptr(dst_cache->cache);
dst = dst_cache_per_cpu_get(dst_cache, idst);
if (!dst)
if (!dst) {
local_unlock_nested_bh(&dst_cache->cache->bh_lock);
return NULL;
}
*saddr = idst->in6_saddr;
local_unlock_nested_bh(&dst_cache->cache->bh_lock);
return dst;
}
EXPORT_SYMBOL_GPL(dst_cache_get_ip6);
@ -142,10 +162,14 @@ EXPORT_SYMBOL_GPL(dst_cache_get_ip6);
int dst_cache_init(struct dst_cache *dst_cache, gfp_t gfp)
{
unsigned int i;
dst_cache->cache = alloc_percpu_gfp(struct dst_cache_pcpu,
gfp | __GFP_ZERO);
if (!dst_cache->cache)
return -ENOMEM;
for_each_possible_cpu(i)
local_lock_init(&per_cpu_ptr(dst_cache->cache, i)->bh_lock);
dst_cache_reset(dst_cache);
return 0;