runtime: eliminate Go -> C -> block paths for Solaris

LGTM=aram, r
R=golang-codereviews, aram, r
CC=golang-codereviews, iant, khr
https://golang.org/cl/141180043

src/pkg/runtime/netpoll.go

@@ -72,7 +72,7 @@ type pollCache struct {
 var pollcache pollCache
 
 func netpollServerInit() {
-	netpollinit()
+	onM(netpollinit)
 }
 
 func netpollOpen(fd uintptr) (*pollDesc, int) {
@@ -93,7 +93,10 @@ func netpollOpen(fd uintptr) (*pollDesc, int) {
 	pd.wd = 0
 	unlock(&pd.lock)
 
-	errno := netpollopen(fd, pd)
+	var errno int32
+	onM(func() {
+		errno = netpollopen(fd, pd)
+	})
 	return pd, int(errno)
 }
 
@@ -107,7 +110,9 @@ func netpollClose(pd *pollDesc) {
 	if pd.rg != 0 && pd.rg != pdReady {
 		gothrow("netpollClose: blocked read on closing descriptor")
 	}
+	onM(func() {
 		netpollclose(uintptr(pd.fd))
+	})
 	pollcache.free(pd)
 }
 
@@ -138,7 +143,9 @@ func netpollWait(pd *pollDesc, mode int) int {
 	}
 	// As for now only Solaris uses level-triggered IO.
 	if GOOS == "solaris" {
+		onM(func() {
 			netpollarm(pd, mode)
+		})
 	}
 	for !netpollblock(pd, int32(mode), false) {
 		err = netpollcheckerr(pd, int32(mode))

src/pkg/runtime/os_solaris.c

@@ -386,36 +386,42 @@ runtime·semawakeup(M *mp)
 		runtime·throw("sem_post");
 }
 
+#pragma textflag NOSPLIT
 int32
 runtime·close(int32 fd)
 {
 	return runtime·sysvicall1(libc·close, (uintptr)fd);
 }
 
+#pragma textflag NOSPLIT
 void
 runtime·exit(int32 r)
 {
 	runtime·sysvicall1(libc·exit, (uintptr)r);
 }
 
+#pragma textflag NOSPLIT
 /* int32 */ void
 runtime·getcontext(Ucontext* context)
 {
 	runtime·sysvicall1(libc·getcontext, (uintptr)context);
 }
 
+#pragma textflag NOSPLIT
 int32
 runtime·getrlimit(int32 res, Rlimit* rlp)
 {
 	return runtime·sysvicall2(libc·getrlimit, (uintptr)res, (uintptr)rlp);
 }
 
+#pragma textflag NOSPLIT
 uint8*
 runtime·mmap(byte* addr, uintptr len, int32 prot, int32 flags, int32 fildes, uint32 off)
 {
 	return (uint8*)runtime·sysvicall6(libc·mmap, (uintptr)addr, (uintptr)len, (uintptr)prot, (uintptr)flags, (uintptr)fildes, (uintptr)off);
 }
 
+#pragma textflag NOSPLIT
 void
 runtime·munmap(byte* addr, uintptr len)
 {
@@ -430,6 +436,7 @@ runtime·nanotime(void)
 	return runtime·sysvicall0((uintptr)runtime·nanotime1);
 }
 
+#pragma textflag NOSPLIT
 void
 time·now(int64 sec, int32 usec)
 {
@@ -442,6 +449,7 @@ time·now(int64 sec, int32 usec)
 	FLUSH(&usec);
 }
 
+#pragma textflag NOSPLIT
 int32
 runtime·open(int8* path, int32 oflag, int32 mode)
 {
@@ -490,6 +498,7 @@ runtime·raise(int32 sig)
 	runtime·sysvicall1(libc·raise, (uintptr)sig);
 }
 
+#pragma textflag NOSPLIT
 int32
 runtime·read(int32 fd, void* buf, int32 nbyte)
 {
@@ -563,6 +572,7 @@ runtime·usleep(uint32 µs)
 	runtime·usleep1(µs);
 }
 
+#pragma textflag NOSPLIT
 int32
 runtime·write(uintptr fd, void* buf, int32 nbyte)
 {

src/pkg/runtime/panic1.go

@@ -138,10 +138,12 @@ func gorecover(argp uintptr) interface{} {
 	return nil
 }
 
+//go:nosplit
 func startpanic() {
 	onM(startpanic_m)
 }
 
+//go:nosplit
 func dopanic(unused int) {
 	gp := getg()
 	mp := acquirem()
@@ -152,10 +154,19 @@ func dopanic(unused int) {
 	*(*int)(nil) = 0
 }
 
+//go:nosplit
 func throw(s *byte) {
-	gothrow(gostringnocopy(s))
+	gp := getg()
+	if gp.m.throwing == 0 {
+		gp.m.throwing = 1
+	}
+	startpanic()
+	print("fatal error: ", gostringnocopy(s), "\n")
+	dopanic(0)
+	*(*int)(nil) = 0 // not reached
 }
 
+//go:nosplit
 func gothrow(s string) {
 	gp := getg()
 	if gp.m.throwing == 0 {