Try harder to avoid deadlocks

By dropping the reply queue lock before actually trying to write,
we reduce the chances that the server won't read our blocking
socket due to us not reading events/replies/etc from earlier.

1 files changed, 14 insertions, 6 deletions

diff --git a/xgob.go b/xgob.go
index fc76de7..76dd579 100644
--- a/xgob.go
+++ b/xgob.go
@@ -45,6 +45,7 @@ type Connection struct {
 	conn				io.ReadWriteCloser
 	reply				map[uint64]chan interface {}
 	replyMutex			sync.Mutex
+	writeMutex			sync.Mutex
 	lastRequestWritten	uint64
 	lastSequenceRead	uint64
 }
@@ -257,6 +258,14 @@ func (c *Connection) fullSeq(seq uint16) uint64 {
 	return fs
 }
 
+func (c *Connection) registerReply (reply chan interface{}) {
+	c.replyMutex.Lock()
+	defer c.replyMutex.Unlock()
+
+	c.lastRequestWritten++
+	c.reply[c.lastRequestWritten] = reply
+}
+
 func (c *Connection) postReply (seq uint64, reply interface{}) {
 	c.replyMutex.Lock()
 	defer c.replyMutex.Unlock()
@@ -350,19 +359,18 @@ func (c *Connection) Disconnect () {
 }
 
 func (c *Connection) WriteMultiRequest (req []byte, expected int) chan interface{} {
-	rv := make(chan interface {}, expected)
-
 	if c == nil || c.conn == nil {
 		return rv
 	}
 
-	c.replyMutex.Lock()
-	defer c.replyMutex.Unlock()
+	rv := make(chan interface {}, expected)
 
-	c.lastRequestWritten++
-	c.reply[c.lastRequestWritten] = rv
+	c.writeMutex.Lock()
+	defer c.writeMutex.Unlock()
 
+	c.registerReply(rv)
 	c.conn.Write(req)
+
 	return rv
 }