runtime: darwin signal masking

Fixes #3101 (darwin).

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5693044

src/pkg/runtime/os_darwin.h

@@ -20,6 +20,9 @@ uint32	runtime·mach_thread_self(void);
 uint32	runtime·mach_thread_self(void);
 int32	runtime·sysctl(uint32*, uint32, byte*, uintptr*, byte*, uintptr);
 
+typedef uint32 Sigset;
+void	runtime·sigprocmask(int32, Sigset*, Sigset*);
+
 struct Sigaction;
 void	runtime·sigaction(uintptr, struct Sigaction*, struct Sigaction*);
 void	runtime·setsig(int32, void(*)(int32, Siginfo*, void*, G*), bool);
@@ -35,3 +38,4 @@ void	runtime·raisesigpipe(void);
 
 #define	NSIG 32
 #define	SI_USER	0  /* empirically true, but not what headers say */
+#define	SIG_SETMASK 3

src/pkg/runtime/sys_darwin_386.s

@@ -106,6 +106,13 @@ TEXT runtime·nanotime(SB), 7, $32
 	MOVL	DX, 4(DI)
 	RET
 
+TEXT runtime·sigprocmask(SB),7,$0
+	MOVL	$48, AX
+	INT	$0x80
+	JAE	2(PC)
+	CALL	runtime·notok(SB)
+	RET
+
 TEXT runtime·sigaction(SB),7,$0
 	MOVL	$46, AX
 	INT	$0x80

src/pkg/runtime/sys_darwin_amd64.s

@@ -92,6 +92,16 @@ TEXT runtime·nanotime(SB), 7, $32
 	ADDQ	DX, AX
 	RET
 
+TEXT runtime·sigprocmask(SB),7,$0
+	MOVL	8(SP), DI
+	MOVQ	16(SP), SI
+	MOVQ	24(SP), DX
+	MOVL	$(0x2000000+48), AX	// syscall entry
+	SYSCALL
+	JCC	2(PC)
+	CALL	runtime·notok(SB)
+	RET
+
 TEXT runtime·sigaction(SB),7,$0
 	MOVL	8(SP), DI		// arg 1 sig
 	MOVQ	16(SP), SI		// arg 2 act

src/pkg/runtime/thread_darwin.c

@@ -9,6 +9,9 @@
 
 extern SigTab runtime·sigtab[];
 
+static Sigset sigset_all = ~(Sigset)0;
+static Sigset sigset_none;
+
 static void
 unimplemented(int8 *name)
 {
@@ -70,13 +73,19 @@ void
 runtime·newosproc(M *m, G *g, void *stk, void (*fn)(void))
 {
 	int32 errno;
+	Sigset oset;
 
 	m->tls[0] = m->id;	// so 386 asm can find it
 	if(0){
 		runtime·printf("newosproc stk=%p m=%p g=%p fn=%p id=%d/%d ostk=%p\n",
 			stk, m, g, fn, m->id, m->tls[0], &m);
 	}
-	if((errno = runtime·bsdthread_create(stk, m, g, fn)) < 0) {
+
+	runtime·sigprocmask(SIG_SETMASK, &sigset_all, &oset);
+	errno = runtime·bsdthread_create(stk, m, g, fn);
+	runtime·sigprocmask(SIG_SETMASK, &oset, nil);
+	
+	if(errno < 0) {
 		runtime·printf("runtime: failed to create new OS thread (have %d already; errno=%d)\n", runtime·mcount(), -errno);
 		runtime·throw("runtime.newosproc");
 	}
@@ -89,6 +98,7 @@ runtime·minit(void)
 	// Initialize signal handling.
 	m->gsignal = runtime·malg(32*1024);	// OS X wants >=8K, Linux >=2K
 	runtime·signalstack(m->gsignal->stackguard - StackGuard, 32*1024);
+	runtime·sigprocmask(SIG_SETMASK, &sigset_none, nil);
 }
 
 // Mach IPC, to get at semaphores