code review 14642044: database/sql: Fix connection leaks and numOpen count

src/pkg/database/sql/sql_test.go

 // Copyright 2011 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 package sql
 
 import (
         "database/sql/driver"
         "errors"
         "fmt"
@@ skipping 76 matching lines @@
                         // their statements first, then we can safely
                         // verify this is always zero here, and any
                         // other value is a leak.
                         t.Errorf("while closing db, freeConn %d/%d had %d open stmts; want 0", i, db.freeConn.Len(), n)
                 }
         }
         err := db.Close()
         if err != nil {
                 t.Fatalf("error closing DB: %v", err)
         }
-        runtime.GC()
-        if db.numOpen != 0 {
+        db.mu.Lock()
+        count := db.numOpen
+        db.mu.Unlock()
+        if count != 0 {
                 t.Fatalf("%d connections still open after closing DB", db.numOpen)
         }
 }
 
 // numPrepares assumes that db has exactly 1 idle conn and returns
 // its count of calls to Prepare
 func numPrepares(t *testing.T, db *DB) int {
         if n := db.freeConn.Len(); n != 1 {
                 t.Fatalf("free conns = %d; want 1", n)
         }
@@ skipping 1622 matching lines @@
         }
 }
 
 func BenchmarkConcurrentRandom(b *testing.B) {
         b.ReportAllocs()
         ct := new(concurrentRandomTest)
         for i := 0; i < b.N; i++ {
                 doConcurrentTest(b, ct)
         }
 }