diff --git a/pkg/conn/baseconn.go b/pkg/conn/baseconn.go
index 86757872be..ee4b0d8276 100644
--- a/pkg/conn/baseconn.go
+++ b/pkg/conn/baseconn.go
@@ -15,6 +15,7 @@ package conn
 
 import (
 	"database/sql"
+	"database/sql/driver"
 	"fmt"
 	"strings"
 
@@ -207,5 +208,14 @@ func (conn *BaseConn) close() error {
 	if conn == nil || conn.DBConn == nil {
 		return nil
 	}
-	return terror.ErrDBUnExpect.Delegate(conn.DBConn.Close(), "close")
+
+	err := conn.DBConn.Raw(func(dc interface{}) error {
+		// return an `ErrBadConn` to ensure close the connection, but do not put it back to the pool.
+		// if we choose to use `Close`, it will always put the connection back to the pool.
+		return driver.ErrBadConn
+	})
+	if err != driver.ErrBadConn {
+		return terror.ErrDBUnExpect.Delegate(err, "close")
+	}
+	return nil
 }
diff --git a/tests/all_mode/run.sh b/tests/all_mode/run.sh
index de61b75765..db36a74e32 100755
--- a/tests/all_mode/run.sh
+++ b/tests/all_mode/run.sh
@@ -5,6 +5,7 @@ set -eu
 cur=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )
 source $cur/../_utils/test_prepare
 WORK_DIR=$TEST_DIR/$TEST_NAME
+API_VERSION="v1alpha1"
 
 function run() {
     export GO_FAILPOINTS="github.com/pingcap/dm/dm/worker/TaskCheckInterval=return(\"500ms\")"
@@ -34,6 +35,10 @@ function run() {
     run_dm_worker $WORK_DIR/worker1 $WORKER1_PORT $cur/conf/dm-worker1.toml
     run_dm_worker $WORK_DIR/worker2 $WORKER2_PORT $cur/conf/dm-worker2.toml
 
+    # wait for task running
+    check_http_alive 127.0.0.1:$MASTER_PORT/apis/${API_VERSION}/status/test '"name":"test","stage":"Running"' 10
+    sleep 2 # still wait for subtask running on other dm-workers
+
     # kill tidb
     pkill -hup tidb-server 2>/dev/null || true
     wait_process_exit tidb-server