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Merged
nickkhyl merged 1 commit into from
Mar 9, 2026
Merged

internal/poll: move rsan to heap on windows #159

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94 changes: 59 additions & 35 deletions src/internal/poll/fd_windows.go
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Original file line number Diff line number Diff line change
Expand Up @@ -149,7 +149,7 @@ var wsaMsgPool = sync.Pool{

// newWSAMsg creates a new WSAMsg with the provided parameters.
// Use [freeWSAMsg] to free it.
func newWSAMsg(p []byte, oob []byte, flags int, unconnected bool) *windows.WSAMsg {
func newWSAMsg(p []byte, oob []byte, flags int, rsa *wsaRsa) *windows.WSAMsg {
// The returned object can't be allocated in the stack because it is accessed asynchronously
// by Windows in between several system calls. If the stack frame is moved while that happens,
// then Windows may access invalid memory.
Expand All @@ -164,34 +164,46 @@ func newWSAMsg(p []byte, oob []byte, flags int, unconnected bool) *windows.WSAMs
Buf: unsafe.SliceData(oob),
}
msg.Flags = uint32(flags)
if unconnected {
msg.Name = wsaRsaPool.Get().(*syscall.RawSockaddrAny)
msg.Namelen = int32(unsafe.Sizeof(syscall.RawSockaddrAny{}))
if rsa != nil {
msg.Name = &rsa.name
msg.Namelen = rsa.namelen
}
return msg
}

func freeWSAMsg(msg *windows.WSAMsg) {
// Clear pointers to buffers so they can be released by garbage collector.
msg.Name = nil
msg.Namelen = 0
msg.Buffers.Len = 0
msg.Buffers.Buf = nil
msg.Control.Len = 0
msg.Control.Buf = nil
if msg.Name != nil {
*msg.Name = syscall.RawSockaddrAny{}
wsaRsaPool.Put(msg.Name)
msg.Name = nil
msg.Namelen = 0
}
wsaMsgPool.Put(msg)
}

// wsaRsa bundles a [syscall.RawSockaddrAny] with its length for efficient caching.
//
// When used by WSARecvFrom, wsaRsa must be on the heap. See
// https://learn.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-wsarecvfrom.
type wsaRsa struct {
name syscall.RawSockaddrAny
namelen int32
}

var wsaRsaPool = sync.Pool{
New: func() any {
return new(syscall.RawSockaddrAny)
return new(wsaRsa)
},
}

func newWSARsa() *wsaRsa {
rsa := wsaRsaPool.Get().(*wsaRsa)
rsa.name = syscall.RawSockaddrAny{}
rsa.namelen = int32(unsafe.Sizeof(syscall.RawSockaddrAny{}))
return rsa
}

var operationPool = sync.Pool{
New: func() any {
return new(operation)
Expand Down Expand Up @@ -737,19 +749,18 @@ func (fd *FD) ReadFrom(buf []byte) (int, syscall.Sockaddr, error) {

fd.pin('r', &buf[0])

rsa := wsaRsaPool.Get().(*syscall.RawSockaddrAny)
rsa := newWSARsa()
defer wsaRsaPool.Put(rsa)
n, err := fd.execIO('r', func(o *operation) (qty uint32, err error) {
rsan := int32(unsafe.Sizeof(*rsa))
var flags uint32
err = syscall.WSARecvFrom(fd.Sysfd, newWsaBuf(buf), 1, &qty, &flags, rsa, &rsan, &o.o, nil)
err = syscall.WSARecvFrom(fd.Sysfd, newWsaBuf(buf), 1, &qty, &flags, &rsa.name, &rsa.namelen, &o.o, nil)
return qty, err
})
err = fd.eofError(n, err)
if err != nil {
return n, nil, err
}
sa, _ := rsa.Sockaddr()
sa, _ := rsa.name.Sockaddr()
return n, sa, nil
}

Expand All @@ -768,19 +779,18 @@ func (fd *FD) ReadFromInet4(buf []byte, sa4 *syscall.SockaddrInet4) (int, error)

fd.pin('r', &buf[0])

rsa := wsaRsaPool.Get().(*syscall.RawSockaddrAny)
rsa := newWSARsa()
defer wsaRsaPool.Put(rsa)
n, err := fd.execIO('r', func(o *operation) (qty uint32, err error) {
rsan := int32(unsafe.Sizeof(*rsa))
var flags uint32
err = syscall.WSARecvFrom(fd.Sysfd, newWsaBuf(buf), 1, &qty, &flags, rsa, &rsan, &o.o, nil)
err = syscall.WSARecvFrom(fd.Sysfd, newWsaBuf(buf), 1, &qty, &flags, &rsa.name, &rsa.namelen, &o.o, nil)
return qty, err
})
err = fd.eofError(n, err)
if err != nil {
return n, err
}
rawToSockaddrInet4(rsa, sa4)
rawToSockaddrInet4(&rsa.name, sa4)
return n, err
}

Expand All @@ -799,19 +809,18 @@ func (fd *FD) ReadFromInet6(buf []byte, sa6 *syscall.SockaddrInet6) (int, error)

fd.pin('r', &buf[0])

rsa := wsaRsaPool.Get().(*syscall.RawSockaddrAny)
rsa := newWSARsa()
defer wsaRsaPool.Put(rsa)
n, err := fd.execIO('r', func(o *operation) (qty uint32, err error) {
rsan := int32(unsafe.Sizeof(*rsa))
var flags uint32
err = syscall.WSARecvFrom(fd.Sysfd, newWsaBuf(buf), 1, &qty, &flags, rsa, &rsan, &o.o, nil)
err = syscall.WSARecvFrom(fd.Sysfd, newWsaBuf(buf), 1, &qty, &flags, &rsa.name, &rsa.namelen, &o.o, nil)
return qty, err
})
err = fd.eofError(n, err)
if err != nil {
return n, err
}
rawToSockaddrInet6(rsa, sa6)
rawToSockaddrInet6(&rsa.name, sa6)
return n, err
}

Expand Down Expand Up @@ -1371,7 +1380,9 @@ func (fd *FD) ReadMsg(p []byte, oob []byte, flags int) (int, int, int, syscall.S
p = p[:maxRW]
}

msg := newWSAMsg(p, oob, flags, true)
rsa := newWSARsa()
defer wsaRsaPool.Put(rsa)
msg := newWSAMsg(p, oob, flags, rsa)
defer freeWSAMsg(msg)
n, err := fd.execIO('r', func(o *operation) (qty uint32, err error) {
err = windows.WSARecvMsg(fd.Sysfd, msg, &qty, &o.o, nil)
Expand All @@ -1396,7 +1407,9 @@ func (fd *FD) ReadMsgInet4(p []byte, oob []byte, flags int, sa4 *syscall.Sockadd
p = p[:maxRW]
}

msg := newWSAMsg(p, oob, flags, true)
rsa := newWSARsa()
defer wsaRsaPool.Put(rsa)
msg := newWSAMsg(p, oob, flags, rsa)
defer freeWSAMsg(msg)
n, err := fd.execIO('r', func(o *operation) (qty uint32, err error) {
err = windows.WSARecvMsg(fd.Sysfd, msg, &qty, &o.o, nil)
Expand All @@ -1420,7 +1433,9 @@ func (fd *FD) ReadMsgInet6(p []byte, oob []byte, flags int, sa6 *syscall.Sockadd
p = p[:maxRW]
}

msg := newWSAMsg(p, oob, flags, true)
rsa := newWSARsa()
defer wsaRsaPool.Put(rsa)
msg := newWSAMsg(p, oob, flags, rsa)
defer freeWSAMsg(msg)
n, err := fd.execIO('r', func(o *operation) (qty uint32, err error) {
err = windows.WSARecvMsg(fd.Sysfd, msg, &qty, &o.o, nil)
Expand All @@ -1444,15 +1459,18 @@ func (fd *FD) WriteMsg(p []byte, oob []byte, sa syscall.Sockaddr) (int, int, err
}
defer fd.writeUnlock()

msg := newWSAMsg(p, oob, 0, sa != nil)
defer freeWSAMsg(msg)
var rsa *wsaRsa
if sa != nil {
rsa = newWSARsa()
defer wsaRsaPool.Put(rsa)
var err error
msg.Namelen, err = sockaddrToRaw(msg.Name, sa)
rsa.namelen, err = sockaddrToRaw(&rsa.name, sa)
if err != nil {
return 0, 0, err
}
}
msg := newWSAMsg(p, oob, 0, rsa)
defer freeWSAMsg(msg)
n, err := fd.execIO('w', func(o *operation) (qty uint32, err error) {
err = windows.WSASendMsg(fd.Sysfd, msg, 0, nil, &o.o, nil)
return qty, err
Expand All @@ -1471,11 +1489,14 @@ func (fd *FD) WriteMsgInet4(p []byte, oob []byte, sa *syscall.SockaddrInet4) (in
}
defer fd.writeUnlock()

msg := newWSAMsg(p, oob, 0, sa != nil)
defer freeWSAMsg(msg)
var rsa *wsaRsa
if sa != nil {
msg.Namelen = sockaddrInet4ToRaw(msg.Name, sa)
rsa = newWSARsa()
defer wsaRsaPool.Put(rsa)
rsa.namelen = sockaddrInet4ToRaw(&rsa.name, sa)
}
msg := newWSAMsg(p, oob, 0, rsa)
defer freeWSAMsg(msg)
n, err := fd.execIO('w', func(o *operation) (qty uint32, err error) {
err = windows.WSASendMsg(fd.Sysfd, msg, 0, nil, &o.o, nil)
return qty, err
Expand All @@ -1494,11 +1515,14 @@ func (fd *FD) WriteMsgInet6(p []byte, oob []byte, sa *syscall.SockaddrInet6) (in
}
defer fd.writeUnlock()

msg := newWSAMsg(p, oob, 0, sa != nil)
defer freeWSAMsg(msg)
var rsa *wsaRsa
if sa != nil {
msg.Namelen = sockaddrInet6ToRaw(msg.Name, sa)
rsa = newWSARsa()
defer wsaRsaPool.Put(rsa)
rsa.namelen = sockaddrInet6ToRaw(&rsa.name, sa)
}
msg := newWSAMsg(p, oob, 0, rsa)
defer freeWSAMsg(msg)
n, err := fd.execIO('w', func(o *operation) (qty uint32, err error) {
err = windows.WSASendMsg(fd.Sysfd, msg, 0, nil, &o.o, nil)
return qty, err
Expand Down
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