runtime: move m's OS-specific semaphore fields into mOS

Allows removing fields that aren't relevant to a particular OS or
changing their types to match the underlying OS system calls they'll
be used for.

Change-Id: I5cea89ee77b4e7b985bff41337e561887c3272ff
Reviewed-on: https://go-review.googlesource.com/16176Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>

src/runtime/lock_sema.go

@@ -13,18 +13,16 @@ import (
 
 // This implementation depends on OS-specific implementations of
 //
-//	uintptr runtime·semacreate(void)
-//		Create a semaphore, which will be assigned to m->waitsema.
-//		The zero value is treated as absence of any semaphore,
-//		so be sure to return a non-zero value.
+//	func semacreate(mp *m)
+//		Create a semaphore for mp, if it does not already have one.
 //
-//	int32 runtime·semasleep(int64 ns)
-//		If ns < 0, acquire m->waitsema and return 0.
-//		If ns >= 0, try to acquire m->waitsema for at most ns nanoseconds.
+//	func semasleep(ns int64) int32
+//		If ns < 0, acquire m's semaphore and return 0.
+//		If ns >= 0, try to acquire m's semaphore for at most ns nanoseconds.
 //		Return 0 if the semaphore was acquired, -1 if interrupted or timed out.
 //
-//	int32 runtime·semawakeup(M *mp)
-//		Wake up mp, which is or will soon be sleeping on mp->waitsema.
+//	func semawakeup(mp *m)
+//		Wake up mp, which is or will soon be sleeping on its semaphore.
 //
 const (
 	locked uintptr = 1
@@ -45,9 +43,7 @@ func lock(l *mutex) {
 	if atomic.Casuintptr(&l.key, 0, locked) {
 		return
 	}
-	if gp.m.waitsema == 0 {
-		gp.m.waitsema = semacreate()
-	}
+	semacreate(gp.m)
 
 	// On uniprocessor's, no point spinning.
 	// On multiprocessors, spin for ACTIVE_SPIN attempts.
@@ -157,9 +153,7 @@ func notesleep(n *note) {
 	if gp != gp.m.g0 {
 		throw("notesleep not on g0")
 	}
-	if gp.m.waitsema == 0 {
-		gp.m.waitsema = semacreate()
-	}
+	semacreate(gp.m)
 	if !atomic.Casuintptr(&n.key, 0, uintptr(unsafe.Pointer(gp.m))) {
 		// Must be locked (got wakeup).
 		if n.key != locked {
@@ -248,9 +242,7 @@ func notetsleep(n *note, ns int64) bool {
 	if gp != gp.m.g0 && gp.m.preemptoff != "" {
 		throw("notetsleep not on g0")
 	}
-	if gp.m.waitsema == 0 {
-		gp.m.waitsema = semacreate()
-	}
+	semacreate(gp.m)
 	return notetsleep_internal(n, ns, nil, 0)
 }
 
@@ -261,9 +253,7 @@ func notetsleepg(n *note, ns int64) bool {
 	if gp == gp.m.g0 {
 		throw("notetsleepg on g0")
 	}
-	if gp.m.waitsema == 0 {
-		gp.m.waitsema = semacreate()
-	}
+	semacreate(gp.m)
 	entersyscallblock(0)
 	ok := notetsleep_internal(n, ns, nil, 0)
 	exitsyscall(0)

src/runtime/os1_darwin.go

@@ -17,16 +17,17 @@ func unimplemented(name string) {
 
 //go:nosplit
 func semawakeup(mp *m) {
-	mach_semrelease(uint32(mp.waitsema))
+	mach_semrelease(mp.waitsema)
 }
 
 //go:nosplit
-func semacreate() uintptr {
-	var x uintptr
+func semacreate(mp *m) {
+	if mp.waitsema != 0 {
+		return
+	}
 	systemstack(func() {
-		x = uintptr(mach_semcreate())
+		mp.waitsema = mach_semcreate()
 	})
-	return x
 }
 
 // BSD interface for threading.
@@ -370,7 +371,7 @@ func semasleep1(ns int64) int32 {
 	if ns >= 0 {
 		var nsecs int32
 		secs := timediv(ns, 1000000000, &nsecs)
-		r := mach_semaphore_timedwait(uint32(_g_.m.waitsema), uint32(secs), uint32(nsecs))
+		r := mach_semaphore_timedwait(_g_.m.waitsema, uint32(secs), uint32(nsecs))
 		if r == _KERN_ABORTED || r == _KERN_OPERATION_TIMED_OUT {
 			return -1
 		}
@@ -381,7 +382,7 @@ func semasleep1(ns int64) int32 {
 	}
 
 	for {
-		r := mach_semaphore_wait(uint32(_g_.m.waitsema))
+		r := mach_semaphore_wait(_g_.m.waitsema)
 		if r == 0 {
 			break
 		}

src/runtime/os1_nacl.go

@@ -83,8 +83,10 @@ func newosproc(mp *m, stk unsafe.Pointer) {
 }
 
 //go:nosplit
-func semacreate() uintptr {
-	var cond uintptr
+func semacreate(mp *m) {
+	if mp.waitsema != 0 {
+		return
+	}
 	systemstack(func() {
 		mu := nacl_mutex_create(0)
 		if mu < 0 {
@@ -93,14 +95,12 @@ func semacreate() uintptr {
 		}
 		c := nacl_cond_create(0)
 		if c < 0 {
-			print("nacl_cond_create: error ", -cond, "\n")
+			print("nacl_cond_create: error ", -c, "\n")
 			throw("semacreate")
 		}
-		cond = uintptr(c)
-		_g_ := getg()
-		_g_.m.waitsemalock = uint32(mu)
+		mp.waitsema = c
+		mp.waitsemalock = mu
 	})
-	return cond
 }
 
 //go:nosplit
@@ -109,13 +109,13 @@ func semasleep(ns int64) int32 {
 
 	systemstack(func() {
 		_g_ := getg()
-		if nacl_mutex_lock(int32(_g_.m.waitsemalock)) < 0 {
+		if nacl_mutex_lock(_g_.m.waitsemalock) < 0 {
 			throw("semasleep")
 		}
 
 		for _g_.m.waitsemacount == 0 {
 			if ns < 0 {
-				if nacl_cond_wait(int32(_g_.m.waitsema), int32(_g_.m.waitsemalock)) < 0 {
+				if nacl_cond_wait(_g_.m.waitsema, _g_.m.waitsemalock) < 0 {
 					throw("semasleep")
 				}
 			} else {
@@ -123,9 +123,9 @@ func semasleep(ns int64) int32 {
 				end := ns + nanotime()
 				ts.tv_sec = end / 1e9
 				ts.tv_nsec = int32(end % 1e9)
-				r := nacl_cond_timed_wait_abs(int32(_g_.m.waitsema), int32(_g_.m.waitsemalock), &ts)
+				r := nacl_cond_timed_wait_abs(_g_.m.waitsema, _g_.m.waitsemalock, &ts)
 				if r == -_ETIMEDOUT {
-					nacl_mutex_unlock(int32(_g_.m.waitsemalock))
+					nacl_mutex_unlock(_g_.m.waitsemalock)
 					ret = -1
 					return
 				}
@@ -136,7 +136,7 @@ func semasleep(ns int64) int32 {
 		}
 
 		_g_.m.waitsemacount = 0
-		nacl_mutex_unlock(int32(_g_.m.waitsemalock))
+		nacl_mutex_unlock(_g_.m.waitsemalock)
 		ret = 0
 	})
 	return ret
@@ -145,15 +145,15 @@ func semasleep(ns int64) int32 {
 //go:nosplit
 func semawakeup(mp *m) {
 	systemstack(func() {
-		if nacl_mutex_lock(int32(mp.waitsemalock)) < 0 {
+		if nacl_mutex_lock(mp.waitsemalock) < 0 {
 			throw("semawakeup")
 		}
 		if mp.waitsemacount != 0 {
 			throw("semawakeup")
 		}
 		mp.waitsemacount = 1
-		nacl_cond_signal(int32(mp.waitsema))
-		nacl_mutex_unlock(int32(mp.waitsemalock))
+		nacl_cond_signal(mp.waitsema)
+		nacl_mutex_unlock(mp.waitsemalock)
 	})
 }
 

src/runtime/os1_netbsd.go

@@ -40,8 +40,7 @@ func getncpu() int32 {
 }
 
 //go:nosplit
-func semacreate() uintptr {
-	return 1
+func semacreate(mp *m) {
 }
 
 //go:nosplit

src/runtime/os1_openbsd.go

@@ -47,8 +47,7 @@ func getncpu() int32 {
 }
 
 //go:nosplit
-func semacreate() uintptr {
-	return 1
+func semacreate(mp *m) {
 }
 
 //go:nosplit

src/runtime/os1_plan9.go

@@ -205,8 +205,7 @@ func newosproc(mp *m, stk unsafe.Pointer) {
 }
 
 //go:nosplit
-func semacreate() uintptr {
-	return 1
+func semacreate(mp *m) {
 }
 
 //go:nosplit

src/runtime/os1_windows.go

@@ -365,8 +365,11 @@ func semawakeup(mp *m) {
 }
 
 //go:nosplit
-func semacreate() uintptr {
-	return stdcall4(_CreateEventA, 0, 0, 0, 0)
+func semacreate(mp *m) {
+	if mp.waitsema != 0 {
+		return
+	}
+	mp.waitsema = stdcall4(_CreateEventA, 0, 0, 0, 0)
 }
 
 // May run with m.p==nil, so write barriers are not allowed.

src/runtime/os3_solaris.go

@@ -314,7 +314,11 @@ func unblocksig(sig int32) {
 }
 
 //go:nosplit
-func semacreate() uintptr {
+func semacreate(mp *m) {
+	if mp.waitsema != 0 {
+		return
+	}
+
 	var sem *semt
 	_g_ := getg()
 
@@ -331,7 +335,7 @@ func semacreate() uintptr {
 	if sem_init(sem, 0, 0) != 0 {
 		throw("sem_init")
 	}
-	return uintptr(unsafe.Pointer(sem))
+	mp.waitsema = uintptr(unsafe.Pointer(sem))
 }
 
 //go:nosplit

src/runtime/os_darwin.go

@@ -6,7 +6,9 @@ package runtime
 
 import "unsafe"
 
-type mOS struct{}
+type mOS struct {
+	waitsema uint32 // semaphore for parking on locks
+}
 
 func bsdthread_create(stk, arg unsafe.Pointer, fn uintptr) int32
 func bsdthread_register() int32

src/runtime/os_nacl.go

@@ -6,7 +6,11 @@ package runtime
 
 import "unsafe"
 
-type mOS struct{}
+type mOS struct {
+	waitsema      int32 // semaphore for parking on locks
+	waitsemacount int32
+	waitsemalock  int32
+}
 
 func nacl_exception_stack(p uintptr, size int32) int32
 func nacl_exception_handler(fn uintptr, arg unsafe.Pointer) int32

src/runtime/os_netbsd.go

@@ -6,7 +6,9 @@ package runtime
 
 import "unsafe"
 
-type mOS struct{}
+type mOS struct {
+	waitsemacount uint32
+}
 
 //go:noescape
 func setitimer(mode int32, new, old *itimerval)

src/runtime/os_openbsd.go

@@ -4,7 +4,9 @@
 
 package runtime
 
-type mOS struct{}
+type mOS struct {
+	waitsemacount uint32
+}
 
 //go:noescape
 func setitimer(mode int32, new, old *itimerval)

src/runtime/os_plan9.go

@@ -7,8 +7,9 @@ package runtime
 import "unsafe"
 
 type mOS struct {
-	notesig *int8
-	errstr  *byte
+	waitsemacount uint32
+	notesig       *int8
+	errstr        *byte
 }
 
 func closefd(fd int32) int32

src/runtime/os_solaris.go

@@ -16,7 +16,8 @@ type mscratch struct {
 }
 
 type mOS struct {
-	perrno *int32 // pointer to tls errno
+	waitsema uintptr // semaphore for parking on locks
+	perrno   *int32  // pointer to tls errno
 	// these are here because they are too large to be on the stack
 	// of low-level NOSPLIT functions.
 	//LibCall       libcall;

src/runtime/os_windows.go

@@ -6,7 +6,9 @@ package runtime
 
 import "unsafe"
 
-type mOS struct{}
+type mOS struct {
+	waitsema uintptr // semaphore for parking on locks
+}
 
 type stdFunction *byte
 

src/runtime/runtime2.go

@@ -308,9 +308,6 @@ type m struct {
 	fflag         uint32      // floating point compare flags
 	locked        uint32      // tracking for lockosthread
 	nextwaitm     uintptr     // next m waiting for lock
-	waitsema      uintptr     // semaphore for parking on locks
-	waitsemacount uint32
-	waitsemalock  uint32
 	gcstats       gcstats
 	needextram    bool
 	traceback     uint8