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internal/poll: do not call SetFileCompletionNotificationModes if it is broken

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Current code assumes that SetFileCompletionNotificationModes
is safe to call even if we know that it is not safe to use
FILE_SKIP_COMPLETION_PORT_ON_SUCCESS flag. It appears (see issue #22149),
SetFileCompletionNotificationModes crashes when we call it without
FILE_SKIP_COMPLETION_PORT_ON_SUCCESS flag.

Do not call SetFileCompletionNotificationModes in that situation.
We are allowed to do that, because SetFileCompletionNotificationModes
is just an optimisation.

Fixes #22149

Change-Id: I0ad3aff4eabd8c27739417a62c286b1819ae166a
Reviewed-on: https://go-review.googlesource.com/69870
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
Alex Brainman 2017-10-11 18:15:25 +11:00
parent 9ce43ce667
commit c37647fc3a
1 changed files with 37 additions and 27 deletions
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64
src/internal/poll/fd_windows.go
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@ -31,11 +31,40 @@ var (
// package uses CancelIoEx API, if present, otherwise it fallback
// to CancelIo.
var (
canCancelIO bool // determines if CancelIoEx API is present
skipSyncNotif bool
hasLoadSetFileCompletionNotificationModes bool
)
var canCancelIO bool // determines if CancelIoEx API is present
// This package uses SetFileCompletionNotificationModes Windows API
// to skip calling GetQueuedCompletionStatus if an IO operation completes
// synchronously. Unfortuently SetFileCompletionNotificationModes is not
// available on Windows XP. Also there is a known bug where
// SetFileCompletionNotificationModes crashes on some systems
// (see http://support.microsoft.com/kb/2568167 for details).
var useSetFileCompletionNotificationModes bool // determines is SetFileCompletionNotificationModes is present and safe to use
// checkSetFileCompletionNotificationModes verifies that
// SetFileCompletionNotificationModes Windows API is present
// on the system and is safe to use.
// See http://support.microsoft.com/kb/2568167 for details.
func checkSetFileCompletionNotificationModes() {
err := syscall.LoadSetFileCompletionNotificationModes()
if err != nil {
return
}
protos := [2]int32{syscall.IPPROTO_TCP, 0}
var buf [32]syscall.WSAProtocolInfo
len := uint32(unsafe.Sizeof(buf))
n, err := syscall.WSAEnumProtocols(&protos[0], &buf[0], &len)
if err != nil {
return
}
for i := int32(0); i < n; i++ {
if buf[i].ServiceFlags1&syscall.XP1_IFS_HANDLES == 0 {
return
}
}
useSetFileCompletionNotificationModes = true
}
func init() {
var d syscall.WSAData
@ -44,26 +73,7 @@ func init() {
initErr = e
}
canCancelIO = syscall.LoadCancelIoEx() == nil
hasLoadSetFileCompletionNotificationModes = syscall.LoadSetFileCompletionNotificationModes() == nil
if hasLoadSetFileCompletionNotificationModes {
// It's not safe to use FILE_SKIP_COMPLETION_PORT_ON_SUCCESS if non IFS providers are installed:
// http://support.microsoft.com/kb/2568167
skipSyncNotif = true
protos := [2]int32{syscall.IPPROTO_TCP, 0}
var buf [32]syscall.WSAProtocolInfo
len := uint32(unsafe.Sizeof(buf))
n, err := syscall.WSAEnumProtocols(&protos[0], &buf[0], &len)
if err != nil {
skipSyncNotif = false
} else {
for i := int32(0); i < n; i++ {
if buf[i].ServiceFlags1&syscall.XP1_IFS_HANDLES == 0 {
skipSyncNotif = false
break
}
}
}
}
checkSetFileCompletionNotificationModes()
}
// operation contains superset of data necessary to perform all async IO.
@ -347,12 +357,12 @@ func (fd *FD) Init(net string, pollable bool) (string, error) {
if err != nil {
return "", err
}
if hasLoadSetFileCompletionNotificationModes {
if useSetFileCompletionNotificationModes {
// We do not use events, so we can skip them always.
flags := uint8(syscall.FILE_SKIP_SET_EVENT_ON_HANDLE)
// It's not safe to skip completion notifications for UDP:
// http://blogs.technet.com/b/winserverperformance/archive/2008/06/26/designing-applications-for-high-performance-part-iii.aspx
if skipSyncNotif && (net == "tcp" || net == "file") {
if net == "tcp" || net == "file" {
flags |= syscall.FILE_SKIP_COMPLETION_PORT_ON_SUCCESS
}
err := syscall.SetFileCompletionNotificationModes(fd.Sysfd, flags)