From 1f96be25b020a56afa330286ee4f241aa14d3983 Mon Sep 17 00:00:00 2001
From: Hennadii Stepanov <32963518+hebasto@users.noreply.github.com>
Date: Mon, 22 Jun 2020 21:12:14 +0300
Subject: Preserve initial state if push_lock() throws exception

---
 src/sync.cpp | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/src/sync.cpp b/src/sync.cpp
index 10f0483189..f72436530e 100644
--- a/src/sync.cpp
+++ b/src/sync.cpp
@@ -149,12 +149,17 @@ static void push_lock(void* c, const CLockLocation& locklocation)
         const LockPair p1 = std::make_pair(i.first, c);
         if (lockdata.lockorders.count(p1))
             continue;
-        lockdata.lockorders.emplace(p1, lock_stack);
 
         const LockPair p2 = std::make_pair(c, i.first);
+        if (lockdata.lockorders.count(p2)) {
+            auto lock_stack_copy = lock_stack;
+            lock_stack.pop_back();
+            potential_deadlock_detected(p1, lockdata.lockorders[p2], lock_stack_copy);
+            // potential_deadlock_detected() does not return.
+        }
+
+        lockdata.lockorders.emplace(p1, lock_stack);
         lockdata.invlockorders.insert(p2);
-        if (lockdata.lockorders.count(p2))
-            potential_deadlock_detected(p1, lockdata.lockorders[p2], lockdata.lockorders[p1]);
     }
 }
 
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