Release deadlock detection flag in case of abnormal transaction termination

Author: knizhnik

src/backend/storage/lmgr/proc.c

@@ -86,6 +86,8 @@ static LOCALLOCK *lockAwaited = NULL;
 
 static DeadLockState deadlock_state = DS_NOT_YET_CHECKED;
 
+static bool inside_deadlock_check = false;
+
 /* Is a deadlock check pending? */
 static volatile sig_atomic_t got_deadlock_timeout;
 
@@ -755,6 +757,14 @@ ProcReleaseLocks(bool isCommit)
 {
 	if (!MyProc)
 		return;
+
+	/* Release deadlock detection flag is backend was interrupted inside deadlock check */
+	if (inside_deadlock_check)
+	{
+		pg_atomic_clear_flag(&ProcGlobal->activeDeadlockCheck);
+		inside_deadlock_check = false;
+	}
+
 	/* If waiting, get off wait queue (should only be needed after error) */
 	LockErrorCleanup();
 	/* Release standard locks, including session-level if aborting */
@@ -1662,6 +1672,14 @@ CheckDeadLock(void)
 	if (!pg_atomic_test_set_flag(&ProcGlobal->activeDeadlockCheck))
 		return;
 
+	/*
+	 * Ensure that only one backend is checking for deadlock.
+	 * Otherwise under high load cascade of deadlock timeout expirations can cause stuck of Postgres.
+	 */
+	if (!pg_atomic_test_set_flag(&ProcGlobal->activeDeadlockCheck))
+		return;
+	inside_deadlock_check = true;
+
 	/*
 	 * Acquire exclusive lock on the entire shared lock data structures. Must
 	 * grab LWLocks in partition-number order to avoid LWLock deadlock.
@@ -1739,6 +1757,7 @@ CheckDeadLock(void)
 		LWLockRelease(LockHashPartitionLockByIndex(i));
 
 	pg_atomic_clear_flag(&ProcGlobal->activeDeadlockCheck);
+	inside_deadlock_check = false;
 }
 
 /*