[GitHub] [doris] yiguolei commented on a diff in pull request #21969: [Bug](storage )fix dead lock when create_tablet need lock two tablet && update mv_p0…

["yiguolei (via GitHub)" <gi...@apache.org>]

yiguolei commented on code in PR #21969:
URL: https://github.com/apache/doris/pull/21969#discussion_r1270819849


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be/src/olap/tablet_manager.cpp:
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@@ -244,7 +244,18 @@ Status TabletManager::create_tablet(const TCreateTabletReq& request, std::vector
     int64_t tablet_id = request.tablet_id;
     LOG(INFO) << "begin to create tablet. tablet_id=" << tablet_id;
 
-    std::lock_guard<std::shared_mutex> wrlock(_get_tablets_shard_lock(tablet_id));
+    // when we create rollup tablet A(assume on shard-1) from tablet B(assume on shard-2)
+    // we need use write lock on shard-1 and then use read lock on shard-2
+    // if there have create rollup tablet C(assume on shard-2) from tablet D(assume on shard-1) at the same time, we will meet deadlock
+    std::unique_lock two_tablet_lock(_two_tablet_mtx, std::defer_lock);
+    bool is_schema_change = request.__isset.base_tablet_id && request.base_tablet_id > 0;
+    bool need_two_lock = is_schema_change && ((_tablets_shards_mask & request.base_tablet_id) !=
+                                              (_tablets_shards_mask & tablet_id));
+    if (need_two_lock) {
+        two_tablet_lock.lock();

Review Comment:
   do not use this lock, maybe forget to unlock or throw exception before unlock.
   maybe use lock guard  + defer lock.



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