Commit 80ca8c3a authored by Thomas Graf's avatar Thomas Graf Committed by David S. Miller

rhashtable: Lower/upper bucket may map to same lock while shrinking

Each per bucket lock covers a configurable number of buckets. While
shrinking, two buckets in the old table contain entries for a single
bucket in the new table. We need to lock down both while linking.
Check if they are protected by different locks to avoid a recursive
lock.

Fixes: 97defe1e ("rhashtable: Per bucket locks & deferred expansion/shrinking")
Reported-by: default avatarFengguang Wu <fengguang.wu@intel.com>
Signed-off-by: default avatarThomas Graf <tgraf@suug.ch>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent df8a39de
......@@ -443,8 +443,16 @@ int rhashtable_shrink(struct rhashtable *ht)
new_bucket_lock = bucket_lock(new_tbl, new_hash);
spin_lock_bh(old_bucket_lock1);
/* Depending on the lock per buckets mapping, the bucket in
* the lower and upper region may map to the same lock.
*/
if (old_bucket_lock1 != old_bucket_lock2) {
spin_lock_bh_nested(old_bucket_lock2, RHT_LOCK_NESTED);
spin_lock_bh_nested(new_bucket_lock, RHT_LOCK_NESTED2);
} else {
spin_lock_bh_nested(new_bucket_lock, RHT_LOCK_NESTED);
}
rcu_assign_pointer(*bucket_tail(new_tbl, new_hash),
tbl->buckets[new_hash]);
......@@ -452,6 +460,7 @@ int rhashtable_shrink(struct rhashtable *ht)
tbl->buckets[new_hash + new_tbl->size]);
spin_unlock_bh(new_bucket_lock);
if (old_bucket_lock1 != old_bucket_lock2)
spin_unlock_bh(old_bucket_lock2);
spin_unlock_bh(old_bucket_lock1);
}
......
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