Merge "[dev.typeparams] all: merge master (46fd547) into dev.typeparams" into dev.typeparamsdev.typeparams

1 files changed, 14 insertions, 6 deletions

diff --git a/src/runtime/cgocall.go b/src/runtime/cgocall.go
index 479878e6d2..2f3c609907 100644
--- a/src/runtime/cgocall.go
+++ b/src/runtime/cgocall.go
@@ -213,6 +213,8 @@ func cgocallbackg(fn, frame unsafe.Pointer, ctxt uintptr) {
 	// a different M. The call to unlockOSThread is in unwindm.
 	lockOSThread()
 
+	checkm := gp.m
+
 	// Save current syscall parameters, so m.syscall can be
 	// used again if callback decide to make syscall.
 	syscall := gp.m.syscall
@@ -228,15 +230,20 @@ func cgocallbackg(fn, frame unsafe.Pointer, ctxt uintptr) {
 
 	osPreemptExtExit(gp.m)
 
-	cgocallbackg1(fn, frame, ctxt)
+	cgocallbackg1(fn, frame, ctxt) // will call unlockOSThread
 
 	// At this point unlockOSThread has been called.
 	// The following code must not change to a different m.
 	// This is enforced by checking incgo in the schedule function.
 
+	gp.m.incgo = true
+
+	if gp.m != checkm {
+		throw("m changed unexpectedly in cgocallbackg")
+	}
+
 	osPreemptExtEnter(gp.m)
 
-	gp.m.incgo = true
 	// going back to cgo call
 	reentersyscall(savedpc, uintptr(savedsp))
 
@@ -245,6 +252,11 @@ func cgocallbackg(fn, frame unsafe.Pointer, ctxt uintptr) {
 
 func cgocallbackg1(fn, frame unsafe.Pointer, ctxt uintptr) {
 	gp := getg()
+
+	// When we return, undo the call to lockOSThread in cgocallbackg.
+	// We must still stay on the same m.
+	defer unlockOSThread()
+
 	if gp.m.needextram || atomic.Load(&extraMWaiters) > 0 {
 		gp.m.needextram = false
 		systemstack(newextram)
@@ -324,10 +336,6 @@ func unwindm(restore *bool) {
 
 		releasem(mp)
 	}
-
-	// Undo the call to lockOSThread in cgocallbackg.
-	// We must still stay on the same m.
-	unlockOSThread()
 }
 
 // called from assembly