libgo patch RFA: Export {enter,exit}syscall

[Ian Lance Taylor <iant at google dot com>]

The cooperative threading model used by Go works by calling entersyscall
whenever we are about to make a call to a C function that may block.
That was not being done for a call to getaddrinfo used when doing a DNS
lookup.  This patch fixes that problem by exporting the entersyscall and
exitsyscall functions from the syscall package.  Exporting a function in
Go is done by naming it with a capital letter, so this patch simply
consistently renames the entersyscall and exitsyscall functions and all
their uses.  This will also be useful for SWIG, which faces a similar
issue.

Bootstrapped and ran Go testsuite on x86_64-unknown-linux-gnu.
Committed to mainline.

OK for 4.7 branch?

Thanks.

Ian

diff -r 89c0a966e4d6 libgo/go/net/cgo_unix.go
--- a/libgo/go/net/cgo_unix.go	Tue Mar 13 13:54:11 2012 -0700
+++ b/libgo/go/net/cgo_unix.go	Tue Mar 13 15:56:25 2012 -0700
@@ -75,7 +75,10 @@
 	}
 
 	s := syscall.StringBytePtr(service)
-	if libc_getaddrinfo(nil, s, &hints, &res) == 0 {
+	syscall.Entersyscall()
+	gerrno := libc_getaddrinfo(nil, s, &hints, &res)
+	syscall.Exitsyscall()
+	if gerrno == 0 {
 		defer libc_freeaddrinfo(res)
 		for r := res; r != nil; r = r.Ai_next {
 			switch r.Ai_family {
@@ -108,7 +111,9 @@
 	hints.Ai_flags = int32((syscall.AI_ALL | syscall.AI_V4MAPPED | syscall.AI_CANONNAME) & cgoAddrInfoMask())
 
 	h := syscall.StringBytePtr(name)
+	syscall.Entersyscall()
 	gerrno := libc_getaddrinfo(h, nil, &hints, &res)
+	syscall.Exitsyscall()
 	if gerrno != 0 {
 		var str string
 		if gerrno == syscall.EAI_NONAME {
diff -r 89c0a966e4d6 libgo/go/syscall/libcall_linux.go
--- a/libgo/go/syscall/libcall_linux.go	Tue Mar 13 13:54:11 2012 -0700
+++ b/libgo/go/syscall/libcall_linux.go	Tue Mar 13 15:56:25 2012 -0700
@@ -202,13 +202,13 @@
 	} else {
 		p = (*byte)(unsafe.Pointer(&_zero))
 	}
-	entersyscall()
+	Entersyscall()
 	r1, _, errno := Syscall(SYS_GETDENTS64, uintptr(fd), uintptr(unsafe.Pointer(p)), uintptr(len(buf)))
 	n = int(r1)
 	if n < 0 {
 		err = errno
 	}
-	exitsyscall()
+	Exitsyscall()
 	return
 }
 
diff -r 89c0a966e4d6 libgo/go/syscall/libcall_support.go
--- a/libgo/go/syscall/libcall_support.go	Tue Mar 13 13:54:11 2012 -0700
+++ b/libgo/go/syscall/libcall_support.go	Tue Mar 13 15:56:25 2012 -0700
@@ -6,7 +6,7 @@
 
 package syscall
 
-func entersyscall()
-func exitsyscall()
+func Entersyscall()
+func Exitsyscall()
 func GetErrno() Errno
 func SetErrno(Errno)
diff -r 89c0a966e4d6 libgo/go/syscall/mksyscall.awk
--- a/libgo/go/syscall/mksyscall.awk	Tue Mar 13 13:54:11 2012 -0700
+++ b/libgo/go/syscall/mksyscall.awk	Tue Mar 13 15:56:25 2012 -0700
@@ -190,7 +190,7 @@
     }
 
     if (blocking) {
-	print "\tentersyscall()"
+	print "\tEntersyscall()"
     }
 
     printf("\t")
@@ -240,7 +240,7 @@
     }
 
     if (blocking) {
-	print "\texitsyscall()"
+	print "\tExitsyscall()"
     }
 
     if (gofnresults != "") {
diff -r 89c0a966e4d6 libgo/go/syscall/syscall_unix.go
--- a/libgo/go/syscall/syscall_unix.go	Tue Mar 13 13:54:11 2012 -0700
+++ b/libgo/go/syscall/syscall_unix.go	Tue Mar 13 15:56:25 2012 -0700
@@ -30,7 +30,7 @@
 // the arguments, so that we don't pass a 64-bit value when the function
 // expects a 32-bit one.
 func Syscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err Errno) {
-	entersyscall()
+	Entersyscall()
 	var r uintptr
 	if unsafe.Sizeof(r) == 4 {
 		r1 := c_syscall32(int32(trap), int32(a1), int32(a2), int32(a3), 0, 0, 0)
@@ -40,12 +40,12 @@
 		r = uintptr(r1)
 	}
 	err = GetErrno()
-	exitsyscall()
+	Exitsyscall()
 	return r, 0, err
 }
 
 func Syscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err Errno) {
-	entersyscall()
+	Entersyscall()
 	var r uintptr
 	if unsafe.Sizeof(r) == 4 {
 		r1 := c_syscall32(int32(trap), int32(a1), int32(a2), int32(a3),
@@ -57,7 +57,7 @@
 		r = uintptr(r1)
 	}
 	err = GetErrno()
-	exitsyscall()
+	Exitsyscall()
 	return r, 0, err
 }
 
diff -r 89c0a966e4d6 libgo/runtime/runtime.h
--- a/libgo/runtime/runtime.h	Tue Mar 13 13:54:11 2012 -0700
+++ b/libgo/runtime/runtime.h	Tue Mar 13 15:56:25 2012 -0700
@@ -298,8 +298,8 @@
 void	runtime_tsleep(int64);
 M*	runtime_newm(void);
 void	runtime_goexit(void);
-void	runtime_entersyscall(void) __asm__("libgo_syscall.syscall.entersyscall");
-void	runtime_exitsyscall(void) __asm__("libgo_syscall.syscall.exitsyscall");
+void	runtime_entersyscall(void) __asm__("libgo_syscall.syscall.Entersyscall");
+void	runtime_exitsyscall(void) __asm__("libgo_syscall.syscall.Exitsyscall");
 void	siginit(void);
 bool	__go_sigsend(int32 sig);
 int32	runtime_callers(int32, uintptr*, int32);