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-rw-r--r--src/qt/clientmodel.cpp16
1 files changed, 15 insertions, 1 deletions
diff --git a/src/qt/clientmodel.cpp b/src/qt/clientmodel.cpp
index f15921c5bc..c1d358f7f6 100644
--- a/src/qt/clientmodel.cpp
+++ b/src/qt/clientmodel.cpp
@@ -116,9 +116,23 @@ int ClientModel::getNumBlocks() const
uint256 ClientModel::getBestBlockHash()
{
+ uint256 tip{WITH_LOCK(m_cached_tip_mutex, return m_cached_tip_blocks)};
+
+ if (!tip.IsNull()) {
+ return tip;
+ }
+
+ // Lock order must be: first `cs_main`, then `m_cached_tip_mutex`.
+ // The following will lock `cs_main` (and release it), so we must not
+ // own `m_cached_tip_mutex` here.
+ tip = m_node.getBestBlockHash();
+
LOCK(m_cached_tip_mutex);
+ // We checked that `m_cached_tip_blocks` is not null above, but then we
+ // released the mutex `m_cached_tip_mutex`, so it could have changed in the
+ // meantime. Thus, check again.
if (m_cached_tip_blocks.IsNull()) {
- m_cached_tip_blocks = m_node.getBestBlockHash();
+ m_cached_tip_blocks = tip;
}
return m_cached_tip_blocks;
}