runtime: clear procid in unminit

Extra Ms can move between system threads. needm will reinitialize procid
(via minit) on the new thread, but leaving a stale procid behind after
dropm can be misleading if printing the M early in needm for debugging.

Change-Id: I668891971a0baeab31170d1e40a97126416e7379
Reviewed-on: https://go-review.googlesource.com/c/go/+/526118
Reviewed-by: Cherry Mui <cherryyz@google.com>
Auto-Submit: Michael Pratt <mpratt@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/runtime/os3_solaris.go

@@ -231,6 +231,7 @@ func minit() {
 // Called from dropm to undo the effect of an minit.
 func unminit() {
 	unminitSignals()
+	getg().m.procid = 0
 }
 
 // Called from exitm, but not from drop, to undo the effect of thread-owned

src/runtime/os_aix.go

@@ -183,6 +183,7 @@ func minit() {
 
 func unminit() {
 	unminitSignals()
+	getg().m.procid = 0
 }
 
 // Called from exitm, but not from drop, to undo the effect of thread-owned

src/runtime/os_darwin.go

@@ -344,6 +344,7 @@ func unminit() {
 	if !(GOOS == "ios" && GOARCH == "arm64") {
 		unminitSignals()
 	}
+	getg().m.procid = 0
 }
 
 // Called from exitm, but not from drop, to undo the effect of thread-owned

src/runtime/os_dragonfly.go

@@ -211,6 +211,7 @@ func minit() {
 //go:nosplit
 func unminit() {
 	unminitSignals()
+	getg().m.procid = 0
 }
 
 // Called from exitm, but not from drop, to undo the effect of thread-owned

src/runtime/os_freebsd.go

@@ -328,6 +328,7 @@ func minit() {
 //go:nosplit
 func unminit() {
 	unminitSignals()
+	getg().m.procid = 0
 }
 
 // Called from exitm, but not from drop, to undo the effect of thread-owned

src/runtime/os_linux.go

@@ -420,6 +420,7 @@ func minit() {
 //go:nosplit
 func unminit() {
 	unminitSignals()
+	getg().m.procid = 0
 }
 
 // Called from exitm, but not from drop, to undo the effect of thread-owned

src/runtime/os_netbsd.go

@@ -316,6 +316,7 @@ func minit() {
 //go:nosplit
 func unminit() {
 	unminitSignals()
+	getg().m.procid = 0
 }
 
 // Called from exitm, but not from drop, to undo the effect of thread-owned

src/runtime/os_openbsd.go

@@ -187,6 +187,7 @@ func minit() {
 //go:nosplit
 func unminit() {
 	unminitSignals()
+	getg().m.procid = 0
 }
 
 // Called from exitm, but not from drop, to undo the effect of thread-owned

src/runtime/os_windows.go

@@ -1010,6 +1010,8 @@ func unminit() {
 		mp.thread = 0
 	}
 	unlock(&mp.threadLock)
+
+	mp.procid = 0
 }
 
 // Called from exitm, but not from drop, to undo the effect of thread-owned