[YSQL] YB does not release LWLocks on AbortTransaction

[timothy-e]

Jira Link: DB-8305

Description

In PostgreSQL when ereport is called with level = ERROR that automatically invokes the AbortTransaction. Currently as part of AbortTransaction, lwlocks held by the Process are not released.
As the locks are not released, that prevents the subsequent acquisition of the lock and causes stuck PostgreSQL processes.

All the lwlocks should be released as part of AbortTransaction. This can happen in any path when lwlock is acquired and ereport is called with level = ERROR .

One Example Scenario which leads to this:

Deadlock when creating replication slots with duplicate names:

select pg_create_logical_replication_slot('test_slot', 'pgoutput');
select pg_create_logical_replication_slot('test_slot', 'pgoutput');
ERROR:  replication slot "test_slot" already exists --> This did not release the acquired locks.
select pg_create_logical_replication_slot('test_slot', 'pgoutput'); -- now deadlocked

Issue Type

kind/bug

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[timothy-e]

There are a seperate type of locks, identified by LOCKTAG that we don't use in YB, so function calls have been disabled. Unfortunately, the LWLockReleaseAll function was accidentally disabled as well.

Fix:

diff --git a/src/postgres/src/backend/access/transam/xact.c b/src/postgres/src/backend/access/transam/xact.c
index 138dc4002f..3fe664da7d 100644
--- a/src/postgres/src/backend/access/transam/xact.c
+++ b/src/postgres/src/backend/access/transam/xact.c
@@ -2691,15 +2691,13 @@ AbortTransaction(void)
        AtAbort_Memory();
        AtAbort_ResourceOwner();
​
-       if (YBIsPgLockingEnabled()) {
-               /*
-               * Release any LW locks we might be holding as quickly as possible.
-               * (Regular locks, however, must be held till we finish aborting.)
-               * Releasing LW locks is critical since we might try to grab them again
-               * while cleaning up!
-               */
-               LWLockReleaseAll();
-       }
+       /*
+        * Release any LW locks we might be holding as quickly as possible.
+        * (Regular locks, however, must be held till we finish aborting.)
+        * Releasing LW locks is critical since we might try to grab them again
+        * while cleaning up!
+        */
+       LWLockReleaseAll();
​
        /* Clear wait information and command progress indicator */
        pgstat_report_wait_end();

[timothy-e]

Closed by 7e22b28

[timothy-e]

Reopening to address on 2.14, 2.16, 2.18, 2.20