runtime: make use of THREAD_SHARE userspace mutex on freebsd

For now Note, futexsleep and futexwakeup are designed for threads,
not for processes. The explicit use of UMTX_OP_WAIT_UINT_PRIVATE and
UMTX_OP_WAKE_PRIVATE can avoid unnecessary traversals of VM objects,
to hit undiscovered bugs related to VM system on SMP/SMT/NUMA
environment.

Update #7496

LGTM=iant
R=golang-codereviews, gobot, iant, bradfitz
CC=golang-codereviews
https://golang.org/cl/72760043

src/pkg/runtime/defs_freebsd.go

@@ -49,8 +49,10 @@ const (
 	SA_RESTART = C.SA_RESTART
 	SA_ONSTACK = C.SA_ONSTACK
 
-	UMTX_OP_WAIT_UINT = C.UMTX_OP_WAIT_UINT
-	UMTX_OP_WAKE      = C.UMTX_OP_WAKE
+	UMTX_OP_WAIT_UINT         = C.UMTX_OP_WAIT_UINT
+	UMTX_OP_WAIT_UINT_PRIVATE = C.UMTX_OP_WAIT_UINT_PRIVATE
+	UMTX_OP_WAKE              = C.UMTX_OP_WAKE
+	UMTX_OP_WAKE_PRIVATE      = C.UMTX_OP_WAKE_PRIVATE
 
 	SIGHUP    = C.SIGHUP
 	SIGINT    = C.SIGINT

src/pkg/runtime/defs_freebsd_386.h

@@ -21,8 +21,10 @@ enum {
 	SA_RESTART	= 0x2,
 	SA_ONSTACK	= 0x1,
 
-	UMTX_OP_WAIT_UINT	= 0xb,
-	UMTX_OP_WAKE		= 0x3,
+	UMTX_OP_WAIT_UINT		= 0xb,
+	UMTX_OP_WAIT_UINT_PRIVATE	= 0xf,
+	UMTX_OP_WAKE			= 0x3,
+	UMTX_OP_WAKE_PRIVATE		= 0x10,
 
 	SIGHUP		= 0x1,
 	SIGINT		= 0x2,

src/pkg/runtime/defs_freebsd_amd64.h

@@ -21,8 +21,10 @@ enum {
 	SA_RESTART	= 0x2,
 	SA_ONSTACK	= 0x1,
 
-	UMTX_OP_WAIT_UINT	= 0xb,
-	UMTX_OP_WAKE		= 0x3,
+	UMTX_OP_WAIT_UINT		= 0xb,
+	UMTX_OP_WAIT_UINT_PRIVATE	= 0xf,
+	UMTX_OP_WAKE			= 0x3,
+	UMTX_OP_WAKE_PRIVATE		= 0x10,
 
 	SIGHUP		= 0x1,
 	SIGINT		= 0x2,

src/pkg/runtime/defs_freebsd_arm.h

@@ -21,8 +21,10 @@ enum {
 	SA_RESTART	= 0x2,
 	SA_ONSTACK	= 0x1,
 
-	UMTX_OP_WAIT_UINT	= 0xb,
-	UMTX_OP_WAKE		= 0x3,
+	UMTX_OP_WAIT_UINT		= 0xb,
+	UMTX_OP_WAIT_UINT_PRIVATE	= 0xf,
+	UMTX_OP_WAKE			= 0x3,
+	UMTX_OP_WAKE_PRIVATE		= 0x10,
 
 	SIGHUP		= 0x1,
 	SIGINT		= 0x2,

src/pkg/runtime/os_freebsd.c

@@ -50,7 +50,7 @@ runtime·futexsleep(uint32 *addr, uint32 val, int64 ns)
 	Timespec ts;
 
 	if(ns < 0) {
-		ret = runtime·sys_umtx_op(addr, UMTX_OP_WAIT_UINT, val, nil, nil);
+		ret = runtime·sys_umtx_op(addr, UMTX_OP_WAIT_UINT_PRIVATE, val, nil, nil);
 		if(ret >= 0 || ret == -EINTR)
 			return;
 		goto fail;
@@ -58,7 +58,7 @@ runtime·futexsleep(uint32 *addr, uint32 val, int64 ns)
 	// NOTE: tv_nsec is int64 on amd64, so this assumes a little-endian system.
 	ts.tv_nsec = 0;
 	ts.tv_sec = runtime·timediv(ns, 1000000000, (int32*)&ts.tv_nsec);
-	ret = runtime·sys_umtx_op(addr, UMTX_OP_WAIT_UINT, val, nil, &ts);
+	ret = runtime·sys_umtx_op(addr, UMTX_OP_WAIT_UINT_PRIVATE, val, nil, &ts);
 	if(ret >= 0 || ret == -EINTR)
 		return;
 
@@ -78,7 +78,7 @@ runtime·futexwakeup(uint32 *addr, uint32 cnt)
 {
 	int32 ret;
 
-	ret = runtime·sys_umtx_op(addr, UMTX_OP_WAKE, cnt, nil, nil);
+	ret = runtime·sys_umtx_op(addr, UMTX_OP_WAKE_PRIVATE, cnt, nil, nil);
 	if(ret >= 0)
 		return;