// loop if gp->atomicstatus is in a scan state giving
// GC time to finish and change the state to oldval.
for !cas(&gp.atomicstatus, oldval, newval) {
+ if oldval == _Gwaiting && gp.atomicstatus == _Grunnable {
+ systemstack(func() {
+ gothrow("casgstatus: waiting for Gwaiting but is Grunnable")
+ })
+ }
+ // Help GC if needed.
+ // if gp.preemptscan && !gp.gcworkdone && (oldval == _Grunning || oldval == _Gsyscall) {
+ // gp.preemptscan = false
+ // systemstack(func() {
+ // gcphasework(gp)
+ // })
+ // }
+ }
+}
+
+// casgstatus(gp, oldstatus, Gcopystack), assuming oldstatus is Gwaiting or Grunnable.
+// Returns old status. Cannot call casgstatus directly, because we are racing with an
+// async wakeup that might come in from netpoll. If we see Gwaiting from the readgstatus,
+// it might have become Grunnable by the time we get to the cas. If we called casgstatus,
+// it would loop waiting for the status to go back to Gwaiting, which it never will.
+//go:nosplit
+func casgcopystack(gp *g) uint32 {
+ for {
+ oldstatus := readgstatus(gp) &^ _Gscan
+ if oldstatus != _Gwaiting && oldstatus != _Grunnable {
+ gothrow("copystack: bad status, not Gwaiting or Grunnable")
+ }
+ if cas(&gp.atomicstatus, oldstatus, _Gcopystack) {
+ return oldstatus
+ }
}
}