Fix race condition in transaction timeout TAP tests

akorotkov · akorotkov · commit 4c2eda67f55a · 2024-03-15T14:38:22.000+02:00
The interruption handler within the injection point can get stuck in an infinite loop while handling transaction timeout. To avoid this situation we reset the timeout flag before invoking the injection point. Author: Alexander Korotkov Reviewed-by: Andrey Borodin Discussion: https://postgr.es/m/ZfPchPC6oNN71X2J%40paquier.xyz
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
@@ -3409,45 +3409,43 @@ ProcessInterrupts(void)
 		/*
 		 * If the GUC has been reset to zero, ignore the signal.  This is
 		 * important because the GUC update itself won't disable any pending
-		 * interrupt.
+		 * interrupt.  We need to unset the flag before the injection point,
+		 * otherwise we could loop in interrupts checking.
 		 */
+		IdleInTransactionSessionTimeoutPending = false;
 		if (IdleInTransactionSessionTimeout > 0)
 		{
 			INJECTION_POINT("idle-in-transaction-session-timeout");
 			ereport(FATAL,
 					(errcode(ERRCODE_IDLE_IN_TRANSACTION_SESSION_TIMEOUT),
 					 errmsg("terminating connection due to idle-in-transaction timeout")));
 		}
-		else
-			IdleInTransactionSessionTimeoutPending = false;
 	}
 
 	if (TransactionTimeoutPending)
 	{
 		/* As above, ignore the signal if the GUC has been reset to zero. */
+		TransactionTimeoutPending = false;
 		if (TransactionTimeout > 0)
 		{
 			INJECTION_POINT("transaction-timeout");
 			ereport(FATAL,
 					(errcode(ERRCODE_TRANSACTION_TIMEOUT),
 					 errmsg("terminating connection due to transaction timeout")));
 		}
-		else
-			TransactionTimeoutPending = false;
 	}
 
 	if (IdleSessionTimeoutPending)
 	{
 		/* As above, ignore the signal if the GUC has been reset to zero. */
+		IdleSessionTimeoutPending = false;
 		if (IdleSessionTimeout > 0)
 		{
 			INJECTION_POINT("idle-session-timeout");
 			ereport(FATAL,
 					(errcode(ERRCODE_IDLE_SESSION_TIMEOUT),
 					 errmsg("terminating connection due to idle-session timeout")));
 		}
-		else
-			IdleSessionTimeoutPending = false;
 	}
 
 	/*

Original file line number	Diff line number	Diff line change
`@@ -3409,45 +3409,43 @@ ProcessInterrupts(void)`
`3409`	`3409`	`/*`
`3410`	`3410`	`* If the GUC has been reset to zero, ignore the signal. This is`
`3411`	`3411`	`* important because the GUC update itself won't disable any pending`
`3412`		`- * interrupt.`
	`3412`	`+ * interrupt. We need to unset the flag before the injection point,`
	`3413`	`+ * otherwise we could loop in interrupts checking.`
`3413`	`3414`	`*/`
	`3415`	`+ IdleInTransactionSessionTimeoutPending = false;`
`3414`	`3416`	`if (IdleInTransactionSessionTimeout > 0)`
`3415`	`3417`	`{`
`3416`	`3418`	`INJECTION_POINT("idle-in-transaction-session-timeout");`
`3417`	`3419`	`ereport(FATAL,`
`3418`	`3420`	`(errcode(ERRCODE_IDLE_IN_TRANSACTION_SESSION_TIMEOUT),`
`3419`	`3421`	`errmsg("terminating connection due to idle-in-transaction timeout")));`
`3420`	`3422`	`}`
`3421`		`- else`
`3422`		`- IdleInTransactionSessionTimeoutPending = false;`
`3423`	`3423`	`}`
`3424`	`3424`
`3425`	`3425`	`if (TransactionTimeoutPending)`
`3426`	`3426`	`{`
`3427`	`3427`	`/* As above, ignore the signal if the GUC has been reset to zero. */`
	`3428`	`+ TransactionTimeoutPending = false;`
`3428`	`3429`	`if (TransactionTimeout > 0)`
`3429`	`3430`	`{`
`3430`	`3431`	`INJECTION_POINT("transaction-timeout");`
`3431`	`3432`	`ereport(FATAL,`
`3432`	`3433`	`(errcode(ERRCODE_TRANSACTION_TIMEOUT),`
`3433`	`3434`	`errmsg("terminating connection due to transaction timeout")));`
`3434`	`3435`	`}`
`3435`		`- else`
`3436`		`- TransactionTimeoutPending = false;`
`3437`	`3436`	`}`
`3438`	`3437`
`3439`	`3438`	`if (IdleSessionTimeoutPending)`
`3440`	`3439`	`{`
`3441`	`3440`	`/* As above, ignore the signal if the GUC has been reset to zero. */`
	`3441`	`+ IdleSessionTimeoutPending = false;`
`3442`	`3442`	`if (IdleSessionTimeout > 0)`
`3443`	`3443`	`{`
`3444`	`3444`	`INJECTION_POINT("idle-session-timeout");`
`3445`	`3445`	`ereport(FATAL,`
`3446`	`3446`	`(errcode(ERRCODE_IDLE_SESSION_TIMEOUT),`
`3447`	`3447`	`errmsg("terminating connection due to idle-session timeout")));`
`3448`	`3448`	`}`
`3449`		`- else`
`3450`		`- IdleSessionTimeoutPending = false;`
`3451`	`3449`	`}`
`3452`	`3450`
`3453`	`3451`	`/*`