From ce6b75dab634e272e0449f85853fca7f1850da8b Mon Sep 17 00:00:00 2001
From: Brad Fitzpatrick <bradfitz@golang.org>
Date: Wed, 7 May 2014 11:54:29 -0700
Subject: [PATCH] database/sql: fix accounting of open connections

Existing test TestMaxOpenConns was failing occasionally, especially
with higher values of GOMAXPROCS.

Fixes #7532

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/95130043
---
 src/pkg/database/sql/sql.go | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/pkg/database/sql/sql.go b/src/pkg/database/sql/sql.go
index 4874574c30..ef54dcdf91 100644
--- a/src/pkg/database/sql/sql.go
+++ b/src/pkg/database/sql/sql.go
@@ -652,13 +652,16 @@ func (db *DB) conn() (*driverConn, error) {
 		return conn, nil
 	}
 
+	db.numOpen++ // optimistically
 	db.mu.Unlock()
 	ci, err := db.driver.Open(db.dsn)
 	if err != nil {
+		db.mu.Lock()
+		db.numOpen-- // correct for earlier optimism
+		db.mu.Unlock()
 		return nil, err
 	}
 	db.mu.Lock()
-	db.numOpen++
 	dc := &driverConn{
 		db: db,
 		ci: ci,