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runtime: handle windows callback on non-go thread

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Adds an extra M in mstartm0 and accounts for it in checkdead. This allows Windows callbacks created with syscall.NewCallback and syscall.NewCallbackCDecl to be called on a non-Go thread.

Fixes #6751

Change-Id: I57626bc009a6370b9ca0827ab64b14b01dec39d4
GitHub-Last-Rev: d429e3eed9
GitHub-Pull-Request: golang/go#25575
Reviewed-on: https://go-review.googlesource.com/114802
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Bill Zissimopoulos 2018-06-03 17:25:29 +00:00 committed by Ian Lance Taylor
parent 4a2bec9726
commit bb0fae603b
2 changed files with 18 additions and 5 deletions
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21
src/runtime/proc.go
View File

@ -1293,7 +1293,9 @@ func mstart1() {
//go:yeswritebarrierrec
func mstartm0() {
// Create an extra M for callbacks on threads not created by Go.
if iscgo && !cgoHasExtraM {
// An extra M is also needed on Windows for callbacks created by
// syscall.NewCallback. See issue #6751 for details.
if (iscgo || GOOS == "windows") && !cgoHasExtraM {
cgoHasExtraM = true
newextram()
}
@ -1618,8 +1620,12 @@ func allocm(_p_ *p, fn func()) *m {
// put the m back on the list.
//go:nosplit
func needm(x byte) {
if iscgo && !cgoHasExtraM {
if (iscgo || GOOS == "windows") && !cgoHasExtraM {
// Can happen if C/C++ code calls Go from a global ctor.
// Can also happen on Windows if a global ctor uses a
// callback created by syscall.NewCallback. See issue #6751
// for details.
//
// Can not throw, because scheduler is not initialized yet.
write(2, unsafe.Pointer(&earlycgocallback[0]), int32(len(earlycgocallback)))
exit(1)
@ -4215,8 +4221,17 @@ func checkdead() {
return
}
// If we are not running under cgo, but we have an extra M then account
// for it. (It is possible to have an extra M on Windows without cgo to
// accommodate callbacks created by syscall.NewCallback. See issue #6751
// for details.)
var run0 int32
if !iscgo && cgoHasExtraM {
run0 = 1
}
run := mcount() - sched.nmidle - sched.nmidlelocked - sched.nmsys
if run > 0 {
if run > run0 {
return
}
if run < 0 {

2
src/runtime/syscall_windows_test.go
View File

@ -251,8 +251,6 @@ func TestBlockingCallback(t *testing.T) {
}
func TestCallbackInAnotherThread(t *testing.T) {
t.Skip("Skipping failing test (see golang.org/issue/6751 for details)")
d := GetDLL(t, "kernel32.dll")
f := func(p uintptr) uintptr {