runtime: unify Unix implementations of unminit

Change-Id: I2cbb13eb85876ad05a52cbd498a9b86e7a28899c
Reviewed-on: https://go-review.googlesource.com/29772
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/runtime/os3_solaris.go

@@ -214,9 +214,7 @@ func minit() {
 
 // Called from dropm to undo the effect of an minit.
 func unminit() {
-	if getg().m.newSigstack {
+	unminitSignals()
-		signalstack(nil)
-	}
 }
 
 func memlimit() uintptr {

src/runtime/os_darwin.go

@@ -188,9 +188,7 @@ func minit() {
 // Called from dropm to undo the effect of an minit.
 //go:nosplit
 func unminit() {
-	if getg().m.newSigstack {
+	unminitSignals()
-		signalstack(nil)
-	}
 }
 
 // Mach IPC, to get at semaphores

src/runtime/os_dragonfly.go

@@ -190,9 +190,7 @@ func minit() {
 // Called from dropm to undo the effect of an minit.
 //go:nosplit
 func unminit() {
-	if getg().m.newSigstack {
+	unminitSignals()
-		signalstack(nil)
-	}
 }
 
 func memlimit() uintptr {

src/runtime/os_freebsd.go

@@ -180,9 +180,7 @@ func minit() {
 // Called from dropm to undo the effect of an minit.
 //go:nosplit
 func unminit() {
-	if getg().m.newSigstack {
+	unminitSignals()
-		signalstack(nil)
-	}
 }
 
 func memlimit() uintptr {

src/runtime/os_linux.go

@@ -266,9 +266,7 @@ func minit() {
 // Called from dropm to undo the effect of an minit.
 //go:nosplit
 func unminit() {
-	if getg().m.newSigstack {
+	unminitSignals()
-		signalstack(nil)
-	}
 }
 
 func memlimit() uintptr {

src/runtime/os_netbsd.go

@@ -244,9 +244,7 @@ func minit() {
 // Called from dropm to undo the effect of an minit.
 //go:nosplit
 func unminit() {
-	if getg().m.newSigstack {
+	unminitSignals()
-		signalstack(nil)
-	}
 }
 
 func memlimit() uintptr {

src/runtime/os_openbsd.go

@@ -223,9 +223,7 @@ func minit() {
 // Called from dropm to undo the effect of an minit.
 //go:nosplit
 func unminit() {
-	if getg().m.newSigstack {
+	unminitSignals()
-		signalstack(nil)
-	}
 }
 
 func memlimit() uintptr {

src/runtime/signal_unix.go

@@ -619,6 +619,15 @@ func minitSignalMask() {
 	sigprocmask(_SIG_SETMASK, &nmask, nil)
 }
 
+// unminitSignals is called from dropm, via unminit, to undo the
+// effect of calling minit on a non-Go thread.
+//go:nosplit
+func unminitSignals() {
+	if getg().m.newSigstack {
+		signalstack(nil)
+	}
+}
+
 // setGsignalStack sets the gsignal stack of the current m to an
 // alternate signal stack returned from the sigaltstack system call.
 // This is used when handling a signal if non-Go code has set the