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Index: head/sys/vm/uma_core.c
===================================================================
--- head/sys/vm/uma_core.c
+++ head/sys/vm/uma_core.c
@@ -4055,6 +4055,7 @@
struct uma_percpu_stat *ups, bool internal)
{
uma_zone_domain_t zdom;
+ uma_bucket_t bucket;
uma_cache_t cache;
int i;
@@ -4068,28 +4069,29 @@
uth->uth_fails = counter_u64_fetch(z->uz_fails);
uth->uth_sleeps = z->uz_sleeps;
uth->uth_xdomain = z->uz_xdomain;
+
/*
- * While it is not normally safe to access the cache
- * bucket pointers while not on the CPU that owns the
- * cache, we only allow the pointers to be exchanged
- * without the zone lock held, not invalidated, so
- * accept the possible race associated with bucket
- * exchange during monitoring.
+ * While it is not normally safe to access the cache bucket pointers
+ * while not on the CPU that owns the cache, we only allow the pointers
+ * to be exchanged without the zone lock held, not invalidated, so
+ * accept the possible race associated with bucket exchange during
+ * monitoring. Use atomic_load_ptr() to ensure that the bucket pointers
+ * are loaded only once.
*/
for (i = 0; i < mp_maxid + 1; i++) {
bzero(&ups[i], sizeof(*ups));
if (internal || CPU_ABSENT(i))
continue;
cache = &z->uz_cpu[i];
- if (cache->uc_allocbucket != NULL)
- ups[i].ups_cache_free +=
- cache->uc_allocbucket->ub_cnt;
- if (cache->uc_freebucket != NULL)
- ups[i].ups_cache_free +=
- cache->uc_freebucket->ub_cnt;
- if (cache->uc_crossbucket != NULL)
- ups[i].ups_cache_free +=
- cache->uc_crossbucket->ub_cnt;
+ bucket = (uma_bucket_t)atomic_load_ptr(&cache->uc_allocbucket);
+ if (bucket != NULL)
+ ups[i].ups_cache_free += bucket->ub_cnt;
+ bucket = (uma_bucket_t)atomic_load_ptr(&cache->uc_freebucket);
+ if (bucket != NULL)
+ ups[i].ups_cache_free += bucket->ub_cnt;
+ bucket = (uma_bucket_t)atomic_load_ptr(&cache->uc_crossbucket);
+ if (bucket != NULL)
+ ups[i].ups_cache_free += bucket->ub_cnt;
ups[i].ups_allocs = cache->uc_allocs;
ups[i].ups_frees = cache->uc_frees;
}

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