net: dst_cache: annotate data-races around dst_cache->reset_ts

dst_cache->reset_ts is read or written locklessly,
add READ_ONCE() and WRITE_ONCE() annotations.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Link: https://lore.kernel.org/r/20240507132000.614591-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: edumazet

include/net/dst_cache.h

@@ -76,7 +76,7 @@ struct dst_entry *dst_cache_get_ip6(struct dst_cache *dst_cache,
  */
 static inline void dst_cache_reset(struct dst_cache *dst_cache)
 {
-	dst_cache->reset_ts = jiffies;
+	WRITE_ONCE(dst_cache->reset_ts, jiffies);
 }
 
 /**

net/core/dst_cache.c

@@ -47,7 +47,8 @@ static struct dst_entry *dst_cache_per_cpu_get(struct dst_cache *dst_cache,
 	/* the cache already hold a dst reference; it can't go away */
 	dst_hold(dst);
 
-	if (unlikely(!time_after(idst->refresh_ts, dst_cache->reset_ts) ||
+	if (unlikely(!time_after(idst->refresh_ts,
+				 READ_ONCE(dst_cache->reset_ts)) ||
 		     (dst->obsolete && !dst->ops->check(dst, idst->cookie)))) {
 		dst_cache_per_cpu_dst_set(idst, NULL, 0);
 		dst_release(dst);
@@ -170,7 +171,7 @@ void dst_cache_reset_now(struct dst_cache *dst_cache)
 	if (!dst_cache->cache)
 		return;
 
-	dst_cache->reset_ts = jiffies;
+	dst_cache_reset(dst_cache);
 	for_each_possible_cpu(i) {
 		struct dst_cache_pcpu *idst = per_cpu_ptr(dst_cache->cache, i);
 		struct dst_entry *dst = idst->dst;