runtime: change GNU/Linux usleep to use nanosleep

Ever since we added sleep to the runtime back in 2008, we've
implemented it on GNU/Linux with the select (or pselect or pselect6)
system call. But the Linux kernel has a nanosleep system call,
which should be a tiny bit more efficient since it doesn't have to
check to see whether there are any file descriptors. So use it.

Change-Id: Icc3430baca46b082a4d33f97c6c47e25fa91cb9a
Reviewed-on: https://go-review.googlesource.com/108538
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/runtime/sys_linux_386.s

@@ -39,6 +39,7 @@
 #define SYS_setittimer		104
 #define SYS_clone		120
 #define SYS_sched_yield 	158
+#define SYS_nanosleep		162
 #define SYS_rt_sigreturn	173
 #define SYS_rt_sigaction	174
 #define SYS_rt_sigprocmask	175
@@ -56,7 +57,6 @@
 #define SYS_epoll_ctl		255
 #define SYS_epoll_wait		256
 #define SYS_clock_gettime	265
-#define SYS_pselect6		308
 #define SYS_epoll_create1	329
 
 TEXT runtime·exit(SB),NOSPLIT,$0
@@ -141,14 +141,10 @@ TEXT runtime·usleep(SB),NOSPLIT,$8
 	MULL	DX
 	MOVL	AX, 4(SP)
 
-	// pselect6(0, 0, 0, 0, &ts, 0)
-	MOVL	$SYS_pselect6, AX
-	MOVL	$0, BX
+	// nanosleep(&ts, 0)
+	MOVL	$SYS_nanosleep, AX
+	LEAL	0(SP), BX
 	MOVL	$0, CX
-	MOVL	$0, DX
-	MOVL	$0, SI
-	LEAL	0(SP), DI
-	MOVL	$0, BP
 	INVOKE_SYSCALL
 	RET
 

src/runtime/sys_linux_amd64.s

@@ -24,6 +24,7 @@
 #define SYS_sched_yield 	24
 #define SYS_mincore		27
 #define SYS_madvise		28
+#define SYS_nanosleep		35
 #define SYS_setittimer		38
 #define SYS_getpid		39
 #define SYS_socket		41
@@ -43,7 +44,6 @@
 #define SYS_epoll_ctl		233
 #define SYS_openat		257
 #define SYS_faccessat		269
-#define SYS_pselect6		270
 #define SYS_epoll_pwait		281
 #define SYS_epoll_create1	291
 
@@ -123,14 +123,10 @@ TEXT runtime·usleep(SB),NOSPLIT,$16
 	MULL	DX
 	MOVQ	AX, 8(SP)
 
-	// pselect6(0, 0, 0, 0, &ts, 0)
-	MOVL	$0, DI
+	// nanosleep(&ts, 0)
+	MOVQ	SP, DI
 	MOVL	$0, SI
-	MOVL	$0, DX
-	MOVL	$0, R10
-	MOVQ	SP, R8
-	MOVL	$0, R9
-	MOVL	$SYS_pselect6, AX
+	MOVL	$SYS_nanosleep, AX
 	SYSCALL
 	RET
 

src/runtime/sys_linux_arm.s

@@ -38,7 +38,7 @@
 #define SYS_gettid (SYS_BASE + 224)
 #define SYS_tkill (SYS_BASE + 238)
 #define SYS_sched_yield (SYS_BASE + 158)
-#define SYS_pselect6 (SYS_BASE + 335)
+#define SYS_nanosleep (SYS_BASE + 162)
 #define SYS_sched_getaffinity (SYS_BASE + 242)
 #define SYS_clock_gettime (SYS_BASE + 263)
 #define SYS_epoll_create (SYS_BASE + 250)
@@ -475,13 +475,9 @@ TEXT runtime·usleep(SB),NOSPLIT,$12
 	MOVW	$1000, R0	// usec to nsec
 	MUL	R0, R1
 	MOVW	R1, 8(R13)
-	MOVW	$0, R0
+	MOVW	$4(R13), R0
 	MOVW	$0, R1
-	MOVW	$0, R2
-	MOVW	$0, R3
-	MOVW	$4(R13), R4
-	MOVW	$0, R5
-	MOVW	$SYS_pselect6, R7
+	MOVW	$SYS_nanosleep, R7
 	SWI	$0
 	RET
 

src/runtime/sys_linux_arm64.s

@@ -21,7 +21,7 @@
 #define SYS_openat		56
 #define SYS_close		57
 #define SYS_fcntl		25
-#define SYS_pselect6		72
+#define SYS_nanosleep		101
 #define SYS_mmap		222
 #define SYS_munmap		215
 #define SYS_setitimer		103
@@ -129,14 +129,10 @@ TEXT runtime·usleep(SB),NOSPLIT,$24-4
 	MUL	R4, R5
 	MOVD	R5, 16(RSP)
 
-	// pselect6(0, 0, 0, 0, &ts, 0)
-	MOVD	$0, R0
-	MOVD	R0, R1
-	MOVD	R0, R2
-	MOVD	R0, R3
-	ADD	$8, RSP, R4
-	MOVD	R0, R5
-	MOVD	$SYS_pselect6, R8
+	// nanosleep(&ts, 0)
+	ADD	$8, RSP, R0
+	MOVD	$0, R1
+	MOVD	$SYS_nanosleep, R8
 	SVC
 	RET
 

src/runtime/sys_linux_mips64x.s

@@ -26,7 +26,7 @@
 #define SYS_munmap		5011
 #define SYS_setitimer		5036
 #define SYS_clone		5055
-#define SYS_newselect		5022
+#define SYS_nanosleep		5034
 #define SYS_sched_yield		5023
 #define SYS_rt_sigreturn	5211
 #define SYS_rt_sigaction	5013
@@ -117,18 +117,16 @@ TEXT runtime·usleep(SB),NOSPLIT,$16-4
 	DIVVU	R4, R3
 	MOVV	LO, R3
 	MOVV	R3, 8(R29)
+	MOVW	$1000, R4
 	MULVU	R3, R4
 	MOVV	LO, R4
 	SUBVU	R4, R5
 	MOVV	R5, 16(R29)
 
-	// select(0, 0, 0, 0, &tv)
-	MOVW	$0, R4
+	// nanosleep(&ts, 0)
+	ADDV	$8, R29, R4
 	MOVW	$0, R5
-	MOVW	$0, R6
-	MOVW	$0, R7
-	ADDV	$8, R29, R8
-	MOVV	$SYS_newselect, R2
+	MOVV	$SYS_nanosleep, R2
 	SYSCALL
 	RET
 

src/runtime/sys_linux_mipsx.s

@@ -26,8 +26,8 @@
 #define SYS_munmap		4091
 #define SYS_setitimer		4104
 #define SYS_clone		4120
-#define SYS_newselect		4142
 #define SYS_sched_yield		4162
+#define SYS_nanosleep		4166
 #define SYS_rt_sigreturn	4193
 #define SYS_rt_sigaction	4194
 #define SYS_rt_sigprocmask	4195
@@ -115,19 +115,16 @@ TEXT runtime·usleep(SB),NOSPLIT,$28-4
 	DIVU	R4, R3
 	MOVW	LO, R3
 	MOVW	R3, 24(R29)
+	MOVW	$1000, R4
 	MULU	R3, R4
 	MOVW	LO, R4
 	SUBU	R4, R5
 	MOVW	R5, 28(R29)
 
-	// select(0, 0, 0, 0, &tv)
-	MOVW	$0, R4
+	// nanosleep(&ts, 0)
+	ADDU	$24, R29, R4
 	MOVW	$0, R5
-	MOVW	$0, R6
-	MOVW	$0, R7
-	ADDU	$24, R29, R8
-	MOVW	R8, 16(R29)
-	MOVW	$SYS_newselect, R2
+	MOVW	$SYS_nanosleep, R2
 	SYSCALL
 	RET
 

src/runtime/sys_linux_ppc64x.s

@@ -27,8 +27,8 @@
 #define SYS_munmap		 91
 #define SYS_setitimer		104
 #define SYS_clone		120
-#define SYS_newselect		142
 #define SYS_sched_yield		158
+#define SYS_nanosleep		162
 #define SYS_rt_sigreturn	172
 #define SYS_rt_sigaction	173
 #define SYS_rt_sigprocmask	174
@@ -106,17 +106,15 @@ TEXT runtime·usleep(SB),NOSPLIT,$16-4
 	MOVW	$1000000, R4
 	DIVD	R4, R3
 	MOVD	R3, 8(R1)
+	MOVW	$1000, R4
 	MULLD	R3, R4
 	SUB	R4, R5
 	MOVD	R5, 16(R1)
 
-	// select(0, 0, 0, 0, &tv)
-	MOVW	$0, R3
+	// nanosleep(&ts, 0)
+	ADD	$8, R1, R3
 	MOVW	$0, R4
-	MOVW	$0, R5
-	MOVW	$0, R6
-	ADD	$8, R1, R7
-	SYSCALL	$SYS_newselect
+	SYSCALL	$SYS_nanosleep
 	RET
 
 TEXT runtime·gettid(SB),NOSPLIT,$0-4

src/runtime/sys_linux_s390x.s

@@ -22,8 +22,8 @@
 #define SYS_munmap               91
 #define SYS_setitimer           104
 #define SYS_clone               120
-#define SYS_select              142
 #define SYS_sched_yield         158
+#define SYS_nanosleep           162
 #define SYS_rt_sigreturn        173
 #define SYS_rt_sigaction        174
 #define SYS_rt_sigprocmask      175
@@ -110,17 +110,15 @@ TEXT runtime·usleep(SB),NOSPLIT,$16-4
 	MOVW	$1000000, R3
 	DIVD	R3, R2
 	MOVD	R2, 8(R15)
+	MOVW	$1000, R3
 	MULLD	R2, R3
 	SUB	R3, R4
 	MOVD	R4, 16(R15)
 
-	// select(0, 0, 0, 0, &tv)
-	MOVW	$0, R2
+	// nanosleep(&ts, 0)
+	ADD	$8, R15, R2
 	MOVW	$0, R3
-	MOVW	$0, R4
-	MOVW	$0, R5
-	ADD	$8, R15, R6
-	MOVW	$SYS_select, R1
+	MOVW	$SYS_nanosleep, R1
 	SYSCALL
 	RET