runtime: correct semaphore implementation on netbsd

NetBSD's semaphores use the underlying lighweight process mechanism
(LWP) on NetBSD, rather than pthreads. This means the m.prodcid needs
to be set to the LWP ID rather than the pthread ID in order for unpark
notifications to get sent to the right place.

Introduce a new getProcID() method that selects the correct ID for the
platform.

Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/261742

gcc/go/gofrontend/MERGE

@@ -1,4 +1,4 @@
-6cb7b9e924d84125f21f4a2a96aa0d59466056fe
+c5505c4e626fa4217911443b4db8b065855a0206
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

libgo/go/runtime/os_aix.go

@@ -21,6 +21,10 @@ type mOS struct {
 	waitsema uintptr // semaphore for parking on locks
 }
 
+func getProcID() uint64 {
+	return uint64(gettid())
+}
+
 //extern malloc
 func libc_malloc(uintptr) unsafe.Pointer
 

libgo/go/runtime/os_gccgo.go

@@ -27,8 +27,7 @@ func mpreinit(mp *m) {
 func minit() {
 	minitSignals()
 
-	// FIXME: only works on linux for now.
-	getg().m.procid = uint64(gettid())
+	getg().m.procid = getProcID()
 }
 
 // Called from dropm to undo the effect of an minit.

libgo/go/runtime/os_hurd.go

@@ -18,6 +18,10 @@ type mOS struct {
 	waitsema uintptr // semaphore for parking on locks
 }
 
+func getProcID() uint64 {
+	return uint64(gettid())
+}
+
 //extern malloc
 func libc_malloc(uintptr) unsafe.Pointer
 

libgo/go/runtime/os_linux.go

@@ -13,6 +13,10 @@ type mOS struct {
 	unused byte
 }
 
+func getProcID() uint64 {
+	return uint64(gettid())
+}
+
 func futex(addr unsafe.Pointer, op int32, val uint32, ts, addr2 unsafe.Pointer, val3 uint32) int32 {
 	return int32(syscall(_SYS_futex, uintptr(addr), uintptr(op), uintptr(val), uintptr(ts), uintptr(addr2), uintptr(val3)))
 }

libgo/go/runtime/os_netbsd.go

@@ -14,12 +14,19 @@ type mOS struct {
 	waitsemacount uint32
 }
 
+func getProcID() uint64 {
+	return uint64(lwp_self())
+}
+
+//extern _lwp_self
+func lwp_self() int32
+
 //go:noescape
-//extern lwp_park
+//extern _lwp_park
 func lwp_park(ts int32, rel int32, abstime *timespec, unpark int32, hint, unparkhint unsafe.Pointer) int32
 
 //go:noescape
-//extern lwp_unpark
+//extern _lwp_unpark
 func lwp_unpark(lwp int32, hint unsafe.Pointer) int32
 
 //go:noescape
@@ -88,7 +95,7 @@ func semasleep(ns int64) int32 {
 			tsp = &ts
 		}
 		ret := lwp_park(_CLOCK_MONOTONIC, _TIMER_RELTIME, tsp, 0, unsafe.Pointer(&_g_.m.waitsemacount), nil)
-		if ret == _ETIMEDOUT {
+		if ret != 0 && errno() == _ETIMEDOUT {
 			return -1
 		}
 	}
@@ -101,10 +108,10 @@ func semawakeup(mp *m) {
 	// "If the target LWP is not currently waiting, it will return
 	// immediately upon the next call to _lwp_park()."
 	ret := lwp_unpark(int32(mp.procid), unsafe.Pointer(&mp.waitsemacount))
-	if ret != 0 && ret != _ESRCH {
+	if ret != 0 && errno() != _ESRCH {
 		// semawakeup can be called on signal stack.
 		systemstack(func() {
-			print("thrwakeup addr=", &mp.waitsemacount, " sem=", mp.waitsemacount, " ret=", ret, "\n")
+			print("thrwakeup addr=", &mp.waitsemacount, " sem=", mp.waitsemacount, " errno=", errno(), "\n")
 		})
 	}
 }

libgo/go/runtime/os_solaris.go

@@ -10,6 +10,10 @@ type mOS struct {
 	waitsema uintptr // semaphore for parking on locks
 }
 
+func getProcID() uint64 {
+	return uint64(gettid())
+}
+
 //extern malloc
 func libc_malloc(uintptr) unsafe.Pointer