From e589c4890b05044a04207c2797e7c8af6693ea5f Mon Sep 17 00:00:00 2001
From: Tomas Vondra <tomas.vondra@postgresql.org>
Date: Fri, 19 Mar 2021 18:12:39 +0100
Subject: [PATCH] Fix race condition in remove_temp_files_after_crash TAP test

The TAP test was written so that it was not waiting for the correct SQL
command, but for output from the preceding one.  This resulted in race
conditions, allowing the commands to run in a different order, not block
as expected and so on.  This fixes it by inverting the order of commands
where possible, so that observing the output guarantees the data was
inserted properly, and waiting for a lock to appear in pg_locks.

Discussion: https://postgr.es/m/CAH503wDKdYzyq7U-QJqGn%3DGm6XmoK%2B6_6xTJ-Yn5WSvoHLY1Ww%40mail.gmail.com
---
 src/test/recovery/t/022_crash_temp_files.pl | 44 ++++++++++++++++++++-
 1 file changed, 42 insertions(+), 2 deletions(-)

diff --git a/src/test/recovery/t/022_crash_temp_files.pl b/src/test/recovery/t/022_crash_temp_files.pl
index 8044849b732..c5624fe8644 100644
--- a/src/test/recovery/t/022_crash_temp_files.pl
+++ b/src/test/recovery/t/022_crash_temp_files.pl
@@ -79,8 +79,8 @@ my $killme2 = IPC::Run::start(
 # Insert one tuple and leave the transaction open
 $killme_stdin2 .= q[
 BEGIN;
-SELECT $$insert-tuple-to-lock-next-insert$$;
 INSERT INTO tab_crash (a) VALUES(1);
+SELECT $$insert-tuple-to-lock-next-insert$$;
 ];
 pump_until($killme2, \$killme_stdout2, qr/insert-tuple-to-lock-next-insert/m);
 $killme_stdout2 = '';
@@ -100,6 +100,26 @@ ok(pump_until($killme, \$killme_stdout, qr/in-progress-before-sigkill/m),
 $killme_stdout = '';
 $killme_stderr = '';
 
+# Wait until the batch insert gets stuck on the lock.
+$killme_stdin2 .= q[
+DO $c$
+DECLARE
+  c INT;
+BEGIN
+  LOOP
+    SELECT COUNT(*) INTO c FROM pg_locks WHERE pid = ] . $pid . q[ AND NOT granted;
+    IF c > 0 THEN
+      EXIT;
+    END IF;
+  END LOOP;
+END; $c$;
+SELECT $$insert-tuple-lock-waiting$$;
+];
+
+pump_until($killme2, \$killme_stdout2, qr/insert-tuple-lock-waiting/m);
+$killme_stdout2 = '';
+$killme_stderr2 = '';
+
 # Kill with SIGKILL
 my $ret = TestLib::system_log('pg_ctl', 'kill', 'KILL', $pid);
 is($ret, 0, 'killed process with KILL');
@@ -147,8 +167,8 @@ $killme2->run();
 # Insert one tuple and leave the transaction open
 $killme_stdin2 .= q[
 BEGIN;
-SELECT $$insert-tuple-to-lock-next-insert$$;
 INSERT INTO tab_crash (a) VALUES(1);
+SELECT $$insert-tuple-to-lock-next-insert$$;
 ];
 pump_until($killme2, \$killme_stdout2, qr/insert-tuple-to-lock-next-insert/m);
 $killme_stdout2 = '';
@@ -168,6 +188,26 @@ ok(pump_until($killme, \$killme_stdout, qr/in-progress-before-sigkill/m),
 $killme_stdout = '';
 $killme_stderr = '';
 
+# Wait until the batch insert gets stuck on the lock.
+$killme_stdin2 .= q[
+DO $c$
+DECLARE
+  c INT;
+BEGIN
+  LOOP
+    SELECT COUNT(*) INTO c FROM pg_locks WHERE pid = ] . $pid . q[ AND NOT granted;
+    IF c > 0 THEN
+      EXIT;
+    END IF;
+  END LOOP;
+END; $c$;
+SELECT $$insert-tuple-lock-waiting$$;
+];
+
+pump_until($killme2, \$killme_stdout2, qr/insert-tuple-lock-waiting/m);
+$killme_stdout2 = '';
+$killme_stderr2 = '';
+
 # Kill with SIGKILL
 $ret = TestLib::system_log('pg_ctl', 'kill', 'KILL', $pid);
 is($ret, 0, 'killed process with KILL');