runtime: sleep on CLOCK_MONOTONIC in futexsleep1 on freebsd

In FreeBSD 10.0, the _umtx_op syscall was changed to allow sleeping on
any supported clock, but the default clock was switched from a monotonic
clock to CLOCK_REALTIME.

Prior to 10.0, the __umtx_op_wait* functions ignored the fourth argument
to _umtx_op (uaddr1), expected the fifth argument (uaddr2) to be a
struct timespec pointer, and used a monotonic clock (nanouptime(9)) for
timeout calculations.

Since 10.0, if callers want a clock other than CLOCK_REALTIME, they must
call _umtx_op with uaddr1 set to a value greater than sizeof(struct
timespec), and with uaddr2 as pointer to a struct _umtx_time, rather
than a timespec. Callers can set the _clockid field of the struct
_umtx_time to request the clock they want.

The relevant FreeBSD commit:
    https://svnweb.freebsd.org/base?view=revision&revision=232144

Fixes #17168

Change-Id: I3dd7b32b683622b8d7b4a6a8f9eb56401bed6bdf
Reviewed-on: https://go-review.googlesource.com/30154
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/runtime/defs_freebsd.go

@@ -23,6 +23,7 @@ package runtime
 #include <sys/mman.h>
 #include <sys/ucontext.h>
 #include <sys/umtx.h>
+#include <sys/_umtx.h>
 #include <sys/rtprio.h>
 #include <sys/thr.h>
 #include <sys/_sigset.h>
@@ -49,6 +50,8 @@ const (
 	SA_RESTART = C.SA_RESTART
 	SA_ONSTACK = C.SA_ONSTACK
 
+	CLOCK_MONOTONIC = C.CLOCK_MONOTONIC
+
 	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
@@ -129,4 +132,6 @@ type Timespec C.struct_timespec
 type Timeval C.struct_timeval
 type Itimerval C.struct_itimerval
 
+type Umtx_time C.struct__umtx_time
+
 type Kevent C.struct_kevent

src/runtime/defs_freebsd_386.go

@@ -24,6 +24,8 @@ const (
 	_SA_RESTART = 0x2
 	_SA_ONSTACK = 0x1
 
+	_CLOCK_MONOTONIC = 0x4
+
 	_UMTX_OP_WAIT_UINT         = 0xb
 	_UMTX_OP_WAIT_UINT_PRIVATE = 0xf
 	_UMTX_OP_WAKE              = 0x3
@@ -197,6 +199,12 @@ type itimerval struct {
 	it_value    timeval
 }
 
+type umtx_time struct {
+	_timeout timespec
+	_flags   uint32
+	_clockid uint32
+}
+
 type keventt struct {
 	ident  uint32
 	filter int16

src/runtime/defs_freebsd_amd64.go

@@ -24,6 +24,8 @@ const (
 	_SA_RESTART = 0x2
 	_SA_ONSTACK = 0x1
 
+	_CLOCK_MONOTONIC = 0x4
+
 	_UMTX_OP_WAIT_UINT         = 0xb
 	_UMTX_OP_WAIT_UINT_PRIVATE = 0xf
 	_UMTX_OP_WAKE              = 0x3
@@ -207,6 +209,12 @@ type itimerval struct {
 	it_value    timeval
 }
 
+type umtx_time struct {
+	_timeout timespec
+	_flags   uint32
+	_clockid uint32
+}
+
 type keventt struct {
 	ident  uint64
 	filter int16

src/runtime/defs_freebsd_arm.go

@@ -24,6 +24,8 @@ const (
 	_SA_RESTART = 0x2
 	_SA_ONSTACK = 0x1
 
+	_CLOCK_MONOTONIC = 0x4
+
 	_UMTX_OP_WAIT_UINT         = 0xb
 	_UMTX_OP_WAIT_UINT_PRIVATE = 0xf
 	_UMTX_OP_WAKE              = 0x3
@@ -170,6 +172,12 @@ type itimerval struct {
 	it_value    timeval
 }
 
+type umtx_time struct {
+	_timeout timespec
+	_flags   uint32
+	_clockid uint32
+}
+
 type keventt struct {
 	ident  uint32
 	filter int16

src/runtime/os_freebsd.go

@@ -35,7 +35,7 @@ func raise(sig uint32)
 func raiseproc(sig uint32)
 
 //go:noescape
-func sys_umtx_op(addr *uint32, mode int32, val uint32, ptr2, ts *timespec) int32
+func sys_umtx_op(addr *uint32, mode int32, val uint32, uaddr1 uintptr, ut *umtx_time) int32
 
 func osyield()
 
@@ -82,14 +82,14 @@ func futexsleep(addr *uint32, val uint32, ns int64) {
 }
 
 func futexsleep1(addr *uint32, val uint32, ns int64) {
-	var tsp *timespec
+	var utp *umtx_time
 	if ns >= 0 {
-		var ts timespec
-		ts.tv_nsec = 0
-		ts.set_sec(int64(timediv(ns, 1000000000, (*int32)(unsafe.Pointer(&ts.tv_nsec)))))
-		tsp = &ts
+		var ut umtx_time
+		ut._clockid = _CLOCK_MONOTONIC
+		ut._timeout.set_sec(int64(timediv(ns, 1000000000, (*int32)(unsafe.Pointer(&ut._timeout.tv_nsec)))))
+		utp = &ut
 	}
-	ret := sys_umtx_op(addr, _UMTX_OP_WAIT_UINT_PRIVATE, val, nil, tsp)
+	ret := sys_umtx_op(addr, _UMTX_OP_WAIT_UINT_PRIVATE, val, unsafe.Sizeof(*utp), utp)
 	if ret >= 0 || ret == -_EINTR {
 		return
 	}
@@ -99,7 +99,7 @@ func futexsleep1(addr *uint32, val uint32, ns int64) {
 
 //go:nosplit
 func futexwakeup(addr *uint32, cnt uint32) {
-	ret := sys_umtx_op(addr, _UMTX_OP_WAKE_PRIVATE, cnt, nil, nil)
+	ret := sys_umtx_op(addr, _UMTX_OP_WAKE_PRIVATE, cnt, 0, nil)
 	if ret >= 0 {
 		return
 	}

src/runtime/sys_freebsd_amd64.s

@@ -14,8 +14,8 @@ TEXT runtime·sys_umtx_op(SB),NOSPLIT,$0
 	MOVQ addr+0(FP), DI
 	MOVL mode+8(FP), SI
 	MOVL val+12(FP), DX
-	MOVQ ptr2+16(FP), R10
-	MOVQ ts+24(FP), R8
+	MOVQ uaddr1+16(FP), R10
+	MOVQ ut+24(FP), R8
 	MOVL $454, AX
 	SYSCALL
 	MOVL	AX, ret+32(FP)

src/runtime/sys_freebsd_arm.s

@@ -45,7 +45,7 @@ TEXT runtime·sys_umtx_op(SB),NOSPLIT,$0
 	MOVW addr+0(FP), R0
 	MOVW mode+4(FP), R1
 	MOVW val+8(FP), R2
-	MOVW ptr2+12(FP), R3
+	MOVW uaddr1+12(FP), R3
 	ADD $20, R13 // arg 5 is passed on stack
 	MOVW $SYS__umtx_op, R7
 	SWI $0