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rwcancel: use poll instead of select 

Suggested-by: Lennart Poettering <lennart@poettering.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
This commit is contained in:
Jason A. Donenfeld 2021-05-20 17:42:34 +02:00
parent 9087e444e6
commit a9b377e9e1
4 changed files with 12 additions and 73 deletions
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24
rwcancel/fdset.go
View File

@ -1,24 +0,0 @@
// +build !windows
/* SPDX-License-Identifier: MIT
*
* Copyright (C) 2017-2021 WireGuard LLC. All Rights Reserved.
*/
package rwcancel
import "golang.org/x/sys/unix"
type fdSet struct {
unix.FdSet
}
func (fdset *fdSet) set(i int) {
bits := 32 << (^uint(0) >> 63)
fdset.Bits[i/bits] |= 1 << uint(i%bits)
}
func (fdset *fdSet) check(i int) bool {
bits := 32 << (^uint(0) >> 63)
return (fdset.Bits[i/bits] & (1 << uint(i%bits))) != 0
}

33
rwcancel/rwcancel.go
View File

@ -17,13 +17,6 @@ import (
"golang.org/x/sys/unix"
)
func max(a, b int) int {
if a > b {
return a
}
return b
}
type RWCancel struct {
fd int
closingReader *os.File
@ -50,13 +43,12 @@ func RetryAfterError(err error) bool {
}
func (rw *RWCancel) ReadyRead() bool {
closeFd := int(rw.closingReader.Fd())
fdset := fdSet{}
fdset.set(rw.fd)
fdset.set(closeFd)
closeFd := int32(rw.closingReader.Fd())
pollFds := []unix.PollFd{{Fd: int32(rw.fd), Events: unix.POLLIN}, {Fd: closeFd, Events: unix.POLLIN}}
var err error
for {
err = unixSelect(max(rw.fd, closeFd)+1, &fdset.FdSet, nil, nil, nil)
_, err = unix.Poll(pollFds, -1)
if err == nil || !RetryAfterError(err) {
break
}
@ -64,20 +56,18 @@ func (rw *RWCancel) ReadyRead() bool {
if err != nil {
return false
}
if fdset.check(closeFd) {
if pollFds[1].Revents != 0 {
return false
}
return fdset.check(rw.fd)
return pollFds[0].Revents != 0
}
func (rw *RWCancel) ReadyWrite() bool {
closeFd := int(rw.closingReader.Fd())
fdset := fdSet{}
fdset.set(rw.fd)
fdset.set(closeFd)
closeFd := int32(rw.closingReader.Fd())
pollFds := []unix.PollFd{{Fd: int32(rw.fd), Events: unix.POLLOUT}, {Fd: closeFd, Events: unix.POLLOUT}}
var err error
for {
err = unixSelect(max(rw.fd, closeFd)+1, nil, &fdset.FdSet, nil, nil)
_, err = unix.Poll(pollFds, -1)
if err == nil || !RetryAfterError(err) {
break
}
@ -85,10 +75,11 @@ func (rw *RWCancel) ReadyWrite() bool {
if err != nil {
return false
}
if fdset.check(closeFd) {
if pollFds[1].Revents != 0 {
return false
}
return fdset.check(rw.fd)
return pollFds[0].Revents != 0
}
func (rw *RWCancel) Read(p []byte) (n int, err error) {

15
rwcancel/select_default.go
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@ -1,15 +0,0 @@
// +build !linux,!windows
/* SPDX-License-Identifier: MIT
*
* Copyright (C) 2017-2021 WireGuard LLC. All Rights Reserved.
*/
package rwcancel
import "golang.org/x/sys/unix"
func unixSelect(nfd int, r *unix.FdSet, w *unix.FdSet, e *unix.FdSet, timeout *unix.Timeval) error {
_, err := unix.Select(nfd, r, w, e, timeout)
return err
}

13
rwcancel/select_linux.go
View File

@ -1,13 +0,0 @@
/* SPDX-License-Identifier: MIT
*
* Copyright (C) 2017-2021 WireGuard LLC. All Rights Reserved.
*/
package rwcancel
import "golang.org/x/sys/unix"
func unixSelect(nfd int, r *unix.FdSet, w *unix.FdSet, e *unix.FdSet, timeout *unix.Timeval) (err error) {
_, err = unix.Select(nfd, r, w, e, timeout)
return
}