3
0
mirror of https://github.com/ergochat/ergo.git synced 2024-12-22 10:42:52 +01:00

fixes to irc/socket.go

* fix a race condition: a call to `Write` does not spawn a writer goroutine
  if the trylock is held, so `BlockingWrite` must check for fresh data after
  releasing the trylock
* streamline some close/finalize logic
This commit is contained in:
Shivaram Lingamneni 2018-11-28 00:24:44 -05:00
parent a0bf548fc5
commit c8cf0befc6

View File

@ -134,6 +134,7 @@ func (socket *Socket) Write(data []byte) (err error) {
prospectiveLen := socket.totalLength + len(data)
if prospectiveLen > socket.maxSendQBytes {
socket.sendQExceeded = true
socket.closed = true
err = errSendQExceeded
} else {
socket.buffers = append(socket.buffers, data)
@ -161,6 +162,13 @@ func (socket *Socket) BlockingWrite(data []byte) (err error) {
return
}
// after releasing the semaphore, we must check for fresh data, same as `send`
defer func() {
if socket.readyToWrite() {
socket.wakeWriter()
}
}()
// blocking acquire of the trylock
socket.writerSemaphore.Acquire()
defer socket.writerSemaphore.Release()
@ -206,7 +214,7 @@ func (socket *Socket) readyToWrite() bool {
socket.Lock()
defer socket.Unlock()
// on the first time observing socket.closed, we still have to write socket.finalData
return !socket.finalized && (socket.totalLength > 0 || socket.closed || socket.sendQExceeded)
return !socket.finalized && (socket.totalLength > 0 || socket.closed)
}
// send actually writes messages to socket.Conn; it may block
@ -238,19 +246,20 @@ func (socket *Socket) performWrite() (closed bool) {
buffers := socket.buffers
socket.buffers = nil
socket.totalLength = 0
closed = socket.closed
socket.Unlock()
// on Linux, the runtime will optimize this into a single writev(2) call:
_, err := (*net.Buffers)(&buffers).WriteTo(socket.conn)
var err error
if !closed && len(buffers) > 0 {
// on Linux, the runtime will optimize this into a single writev(2) call:
_, err = (*net.Buffers)(&buffers).WriteTo(socket.conn)
}
socket.Lock()
shouldClose := (err != nil) || socket.closed || socket.sendQExceeded
socket.Unlock()
if shouldClose {
closed = closed || err != nil
if closed {
socket.finalize()
}
return shouldClose
return
}
// mark closed and send final data. you must be holding the semaphore to call this:
@ -258,12 +267,18 @@ func (socket *Socket) finalize() {
// mark the socket closed (if someone hasn't already), then write error lines
socket.Lock()
socket.closed = true
finalized := socket.finalized
socket.finalized = true
finalData := socket.finalData
if socket.sendQExceeded {
finalData = "\r\nERROR :SendQ Exceeded\r\n"
}
socket.Unlock()
if finalized {
return
}
if finalData != "" {
socket.conn.Write([]byte(finalData))
}