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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Thomas Gleixner , Sebastian Andrzej Siewior Subject: [PATCH net-next v2 02/18] net: dst_cache: Use nested-BH locking for dst_cache::cache Date: Mon, 14 Apr 2025 18:07:38 +0200 Message-ID: <20250414160754.503321-3-bigeasy@linutronix.de> In-Reply-To: <20250414160754.503321-1-bigeasy@linutronix.de> References: <20250414160754.503321-1-bigeasy@linutronix.de> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: kuba@kernel.org 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 --- net/core/dst_cache.c | 30 +++++++++++++++++++++++++++--- 1 file changed, 27 insertions(+), 3 deletions(-) diff --git a/net/core/dst_cache.c b/net/core/dst_cache.c index 70c634b9e7b02..93a04d18e5054 100644 --- a/net/core/dst_cache.c +++ b/net/core/dst_cache.c @@ -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;