electrum

commit 4acf884790b2136dcff7948e975460f11cf0aa93
parent 36178df875eef5186b9c25622b7b5ae345776ecf
Author: SomberNight <somber.night@protonmail.com>
Date:   Tue, 25 Aug 2020 20:29:08 +0200

blockchain.py: maybe fix rare deadlock

Saw a deadlock near a swap_with_parent(), could not reproduce.
get_branch_size() and get_parent_heights() could have been the culprits as
they take locks in differing orders and are called from gui/network threads.

Diffstat:
M
electrum/blockchain.py
 | 
4
++--

1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/electrum/blockchain.py b/electrum/blockchain.py
@@ -86,7 +86,7 @@ def hash_raw_header(header: str) -> str:
 # key: blockhash hex at forkpoint
 # the chain at some key is the best chain that includes the given hash
 blockchains = {}  # type: Dict[str, Blockchain]
-blockchains_lock = threading.RLock()
+blockchains_lock = threading.RLock()  # lock order: take this last; so after Blockchain.lock
 
 
 def read_blockchains(config: 'SimpleConfig'):
@@ -222,7 +222,7 @@ class Blockchain(Logger):
 
     def get_parent_heights(self) -> Mapping['Blockchain', int]:
         """Returns map: (parent chain -> height of last common block)"""
-        with blockchains_lock:
+        with self.lock, blockchains_lock:
             result = {self: self.height()}
             chain = self
             while True: