Fix significant drop in match scrutinee

rust-lang/rust#93883
ZcashFoundation · Jun 7, 2022 · 3b895cd · 3b895cd
1 parent 00aa64a
commit 3b895cd
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Showing 4 changed files with 15 additions and 6 deletions.
diff --git a/zebra-chain/src/orchard/tree.rs b/zebra-chain/src/orchard/tree.rs
@@ -335,7 +335,8 @@ impl NoteCommitmentTree {
             .cached_root
             .write()
             .expect("a thread that previously held exclusive lock access panicked");
-        match *write_root {
+        let read_root = write_root.as_ref().cloned();
+        match read_root {
             // Another thread got write access first, return cached root.
             Some(root) => root,
             None => {

diff --git a/zebra-chain/src/sapling/tree.rs b/zebra-chain/src/sapling/tree.rs
@@ -340,7 +340,8 @@ impl NoteCommitmentTree {
             .cached_root
             .write()
             .expect("a thread that previously held exclusive lock access panicked");
-        match *write_root {
+        let read_root = write_root.as_ref().cloned();
+        match read_root {
             // Another thread got write access first, return cached root.
             Some(root) => root,
             None => {

diff --git a/zebra-chain/src/sprout/tree.rs b/zebra-chain/src/sprout/tree.rs
@@ -274,7 +274,8 @@ impl NoteCommitmentTree {
             .cached_root
             .write()
             .expect("a thread that previously held exclusive lock access panicked");
-        match *write_root {
+        let read_root = write_root.as_ref().cloned();
+        match read_root {
             // Another thread got write access first, return cached root.
             Some(root) => root,
             None => {

diff --git a/zebra-state/src/service/chain_tip.rs b/zebra-state/src/service/chain_tip.rs
@@ -195,12 +195,18 @@ impl ChainTipSender {
         // a read-lock being created and living beyond the `self.sender.send(..)` call. If that
         // happens, the `send` method will attempt to obtain a write-lock and will dead-lock.
         // Without the binding, the guard is dropped at the end of the expression.
-        let needs_update = match (new_tip.as_ref(), self.sender.borrow().as_ref()) {
+        let active_hash = self
+            .sender
+            .borrow()
+            .as_ref()
+            .map(|active_value| active_value.hash);
+
+        let needs_update = match (new_tip.as_ref(), active_hash) {
             // since the blocks have been contextually validated,
             // we know their hashes cover all the block data
-            (Some(new_tip), Some(active_value)) => new_tip.hash != active_value.hash,
+            (Some(new_tip), Some(active_hash)) => new_tip.hash != active_hash,
             (Some(_new_tip), None) => true,
-            (None, _active_value) => false,
+            (None, _active_value_hash) => false,
         };
 
         if needs_update {