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internal/poll: only start Windows goroutines when we need them

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We don't need to start the goroutines if the program isn't going to do
any I/O.

Fixes #19390.

Change-Id: I47eef992d3ad05ed5f3150f4d6e5b3e0cb16a551
Reviewed-on: https://go-review.googlesource.com/37762
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
This commit is contained in:
Ian Lance Taylor 2017-03-03 17:15:11 -08:00
parent 5ce06cf71d
commit 61d9cd73fb
1 changed files with 13 additions and 13 deletions
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26
src/internal/poll/fd_windows.go
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@ -154,6 +154,10 @@ func (s *ioSrv) ProcessRemoteIO() {
// is available. Alternatively, it passes the request onto
// runtime netpoll and waits for completion or cancels request.
func (s *ioSrv) ExecIO(o *operation, name string, submit func(o *operation) error) (int, error) {
if !canCancelIO {
onceStartServer.Do(startServer)
}
fd := o.fd
// Notify runtime netpoll about starting IO.
err := fd.pd.prepare(int(o.mode))
@ -229,21 +233,18 @@ func (s *ioSrv) ExecIO(o *operation, name string, submit func(o *operation) erro
}
// Start helper goroutines.
var rsrv, wsrv *ioSrv
var rsrv, wsrv ioSrv
var onceStartServer sync.Once
func startServer() {
rsrv = new(ioSrv)
wsrv = new(ioSrv)
if !canCancelIO {
// Only CancelIo API is available. Lets start two special goroutines
// locked to an OS thread, that both starts and cancels IO. One will
// process read requests, while other will do writes.
rsrv.req = make(chan ioSrvReq)
go rsrv.ProcessRemoteIO()
wsrv.req = make(chan ioSrvReq)
go wsrv.ProcessRemoteIO()
}
// This is called, once, when only the CancelIo API is available.
// Start two special goroutines, both locked to an OS thread,
// that start and cancel IO requests.
// One will process read requests, while the other will do writes.
rsrv.req = make(chan ioSrvReq)
go rsrv.ProcessRemoteIO()
wsrv.req = make(chan ioSrvReq)
go wsrv.ProcessRemoteIO()
}
// FD is a file descriptor. The net and os packages embed this type in
@ -298,7 +299,6 @@ func (fd *FD) Init(net string) (string, error) {
if initErr != nil {
return "", initErr
}
onceStartServer.Do(startServer)
switch net {
case "file":