unix: add Eventfd function on Linux

Add support for the eventfd2 syscall on Linux.

Use the eventfd2 syscall instead of eventfd, as the latter does not
provide a flags argument and glibc also maps its eventfd() function to
the eventfd2 syscall, see the Notes section in
http://man7.org/linux/man-pages/man2/eventfd.2.html

Also add the corresponding flags values EFD_CLOEXEC, EFD_NONBLOCK and
EFD_SEMAPHORE.

Change-Id: Ia8c99e68d5966ab5c7ebe7e45423943fd7d8214e
Reviewed-on: https://go-review.googlesource.com/45093
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/unix/mkerrors.sh b/unix/mkerrors.sh
index e38b4ca..d56eb43 100755
--- a/unix/mkerrors.sh
+++ b/unix/mkerrors.sh
@@ -143,6 +143,7 @@
 
 #include <bits/sockaddr.h>
 #include <sys/epoll.h>
+#include <sys/eventfd.h>
 #include <sys/inotify.h>
 #include <sys/ioctl.h>
 #include <sys/mman.h>
@@ -375,7 +376,7 @@
 		$2 ~ /^SYSCTL_VERS/ ||
 		$2 ~ /^(MS|MNT)_/ ||
 		$2 ~ /^TUN(SET|GET|ATTACH|DETACH)/ ||
-		$2 ~ /^(O|F|FD|NAME|S|PTRACE|PT)_/ ||
+		$2 ~ /^(O|F|E?FD|NAME|S|PTRACE|PT)_/ ||
 		$2 ~ /^LINUX_REBOOT_CMD_/ ||
 		$2 ~ /^LINUX_REBOOT_MAGIC[12]$/ ||
 		$2 !~ "NLA_TYPE_MASK" &&
diff --git a/unix/syscall_linux.go b/unix/syscall_linux.go
index 6fd0ab8..77f9c54 100644
--- a/unix/syscall_linux.go
+++ b/unix/syscall_linux.go
@@ -1171,6 +1171,7 @@
 //sysnb	EpollCreate(size int) (fd int, err error)
 //sysnb	EpollCreate1(flag int) (fd int, err error)
 //sysnb	EpollCtl(epfd int, op int, fd int, event *EpollEvent) (err error)
+//sys	Eventfd(initval uint, flags int) (fd int, err error) = SYS_EVENTFD2
 //sys	Exit(code int) = SYS_EXIT_GROUP
 //sys	Faccessat(dirfd int, path string, mode uint32, flags int) (err error)
 //sys	Fallocate(fd int, mode uint32, off int64, len int64) (err error)
@@ -1316,7 +1317,6 @@
 // EpollCtlOld
 // EpollPwait
 // EpollWaitOld
-// Eventfd
 // Execve
 // Fgetxattr
 // Flistxattr
diff --git a/unix/zerrors_linux_386.go b/unix/zerrors_linux_386.go
index 5a9e559..e8d945e 100644
--- a/unix/zerrors_linux_386.go
+++ b/unix/zerrors_linux_386.go
@@ -325,6 +325,9 @@
 	ECHOKE                               = 0x800
 	ECHONL                               = 0x40
 	ECHOPRT                              = 0x400
+	EFD_CLOEXEC                          = 0x80000
+	EFD_NONBLOCK                         = 0x800
+	EFD_SEMAPHORE                        = 0x1
 	ENCODING_DEFAULT                     = 0x0
 	ENCODING_FM_MARK                     = 0x3
 	ENCODING_FM_SPACE                    = 0x4
diff --git a/unix/zerrors_linux_amd64.go b/unix/zerrors_linux_amd64.go
index 1f465d6..97dc039 100644
--- a/unix/zerrors_linux_amd64.go
+++ b/unix/zerrors_linux_amd64.go
@@ -325,6 +325,9 @@
 	ECHOKE                               = 0x800
 	ECHONL                               = 0x40
 	ECHOPRT                              = 0x400
+	EFD_CLOEXEC                          = 0x80000
+	EFD_NONBLOCK                         = 0x800
+	EFD_SEMAPHORE                        = 0x1
 	ENCODING_DEFAULT                     = 0x0
 	ENCODING_FM_MARK                     = 0x3
 	ENCODING_FM_SPACE                    = 0x4
diff --git a/unix/zerrors_linux_arm.go b/unix/zerrors_linux_arm.go
index 6475eb7..52f08f2 100644
--- a/unix/zerrors_linux_arm.go
+++ b/unix/zerrors_linux_arm.go
@@ -325,6 +325,9 @@
 	ECHOKE                               = 0x800
 	ECHONL                               = 0x40
 	ECHOPRT                              = 0x400
+	EFD_CLOEXEC                          = 0x80000
+	EFD_NONBLOCK                         = 0x800
+	EFD_SEMAPHORE                        = 0x1
 	ENCODING_DEFAULT                     = 0x0
 	ENCODING_FM_MARK                     = 0x3
 	ENCODING_FM_SPACE                    = 0x4
diff --git a/unix/zerrors_linux_arm64.go b/unix/zerrors_linux_arm64.go
index 161bca7..0cfe25b 100644
--- a/unix/zerrors_linux_arm64.go
+++ b/unix/zerrors_linux_arm64.go
@@ -325,6 +325,9 @@
 	ECHOKE                               = 0x800
 	ECHONL                               = 0x40
 	ECHOPRT                              = 0x400
+	EFD_CLOEXEC                          = 0x80000
+	EFD_NONBLOCK                         = 0x800
+	EFD_SEMAPHORE                        = 0x1
 	ENCODING_DEFAULT                     = 0x0
 	ENCODING_FM_MARK                     = 0x3
 	ENCODING_FM_SPACE                    = 0x4
diff --git a/unix/zerrors_linux_mips.go b/unix/zerrors_linux_mips.go
index f4d0b9c..264a136 100644
--- a/unix/zerrors_linux_mips.go
+++ b/unix/zerrors_linux_mips.go
@@ -325,6 +325,9 @@
 	ECHOKE                               = 0x800
 	ECHONL                               = 0x40
 	ECHOPRT                              = 0x400
+	EFD_CLOEXEC                          = 0x80000
+	EFD_NONBLOCK                         = 0x80
+	EFD_SEMAPHORE                        = 0x1
 	ENCODING_DEFAULT                     = 0x0
 	ENCODING_FM_MARK                     = 0x3
 	ENCODING_FM_SPACE                    = 0x4
diff --git a/unix/zerrors_linux_mips64.go b/unix/zerrors_linux_mips64.go
index 10f130e..bde3efb 100644
--- a/unix/zerrors_linux_mips64.go
+++ b/unix/zerrors_linux_mips64.go
@@ -325,6 +325,9 @@
 	ECHOKE                               = 0x800
 	ECHONL                               = 0x40
 	ECHOPRT                              = 0x400
+	EFD_CLOEXEC                          = 0x80000
+	EFD_NONBLOCK                         = 0x80
+	EFD_SEMAPHORE                        = 0x1
 	ENCODING_DEFAULT                     = 0x0
 	ENCODING_FM_MARK                     = 0x3
 	ENCODING_FM_SPACE                    = 0x4
diff --git a/unix/zerrors_linux_mips64le.go b/unix/zerrors_linux_mips64le.go
index 5570e26..167c228 100644
--- a/unix/zerrors_linux_mips64le.go
+++ b/unix/zerrors_linux_mips64le.go
@@ -325,6 +325,9 @@
 	ECHOKE                               = 0x800
 	ECHONL                               = 0x40
 	ECHOPRT                              = 0x400
+	EFD_CLOEXEC                          = 0x80000
+	EFD_NONBLOCK                         = 0x80
+	EFD_SEMAPHORE                        = 0x1
 	ENCODING_DEFAULT                     = 0x0
 	ENCODING_FM_MARK                     = 0x3
 	ENCODING_FM_SPACE                    = 0x4
diff --git a/unix/zerrors_linux_mipsle.go b/unix/zerrors_linux_mipsle.go
index 4184959..6c47abf 100644
--- a/unix/zerrors_linux_mipsle.go
+++ b/unix/zerrors_linux_mipsle.go
@@ -325,6 +325,9 @@
 	ECHOKE                               = 0x800
 	ECHONL                               = 0x40
 	ECHOPRT                              = 0x400
+	EFD_CLOEXEC                          = 0x80000
+	EFD_NONBLOCK                         = 0x80
+	EFD_SEMAPHORE                        = 0x1
 	ENCODING_DEFAULT                     = 0x0
 	ENCODING_FM_MARK                     = 0x3
 	ENCODING_FM_SPACE                    = 0x4
diff --git a/unix/zerrors_linux_ppc64.go b/unix/zerrors_linux_ppc64.go
index ab64fcb..32eccbd 100644
--- a/unix/zerrors_linux_ppc64.go
+++ b/unix/zerrors_linux_ppc64.go
@@ -325,6 +325,9 @@
 	ECHOKE                               = 0x1
 	ECHONL                               = 0x10
 	ECHOPRT                              = 0x20
+	EFD_CLOEXEC                          = 0x80000
+	EFD_NONBLOCK                         = 0x800
+	EFD_SEMAPHORE                        = 0x1
 	ENCODING_DEFAULT                     = 0x0
 	ENCODING_FM_MARK                     = 0x3
 	ENCODING_FM_SPACE                    = 0x4
diff --git a/unix/zerrors_linux_ppc64le.go b/unix/zerrors_linux_ppc64le.go
index 0ebbf94..eb944e6 100644
--- a/unix/zerrors_linux_ppc64le.go
+++ b/unix/zerrors_linux_ppc64le.go
@@ -325,6 +325,9 @@
 	ECHOKE                               = 0x1
 	ECHONL                               = 0x10
 	ECHOPRT                              = 0x20
+	EFD_CLOEXEC                          = 0x80000
+	EFD_NONBLOCK                         = 0x800
+	EFD_SEMAPHORE                        = 0x1
 	ENCODING_DEFAULT                     = 0x0
 	ENCODING_FM_MARK                     = 0x3
 	ENCODING_FM_SPACE                    = 0x4
diff --git a/unix/zerrors_linux_s390x.go b/unix/zerrors_linux_s390x.go
index d01da43..3566349 100644
--- a/unix/zerrors_linux_s390x.go
+++ b/unix/zerrors_linux_s390x.go
@@ -325,6 +325,9 @@
 	ECHOKE                               = 0x800
 	ECHONL                               = 0x40
 	ECHOPRT                              = 0x400
+	EFD_CLOEXEC                          = 0x80000
+	EFD_NONBLOCK                         = 0x800
+	EFD_SEMAPHORE                        = 0x1
 	ENCODING_DEFAULT                     = 0x0
 	ENCODING_FM_MARK                     = 0x3
 	ENCODING_FM_SPACE                    = 0x4
diff --git a/unix/zsyscall_linux_386.go b/unix/zsyscall_linux_386.go
index 0c2a808..51de848 100644
--- a/unix/zsyscall_linux_386.go
+++ b/unix/zsyscall_linux_386.go
@@ -511,6 +511,17 @@
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
+func Eventfd(initval uint, flags int) (fd int, err error) {
+	r0, _, e1 := Syscall(SYS_EVENTFD2, uintptr(initval), uintptr(flags), 0)
+	fd = int(r0)
+	if e1 != 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
 func Exit(code int) {
 	Syscall(SYS_EXIT_GROUP, uintptr(code), 0, 0)
 	return
diff --git a/unix/zsyscall_linux_amd64.go b/unix/zsyscall_linux_amd64.go
index f74c341..19f9fe5 100644
--- a/unix/zsyscall_linux_amd64.go
+++ b/unix/zsyscall_linux_amd64.go
@@ -511,6 +511,17 @@
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
+func Eventfd(initval uint, flags int) (fd int, err error) {
+	r0, _, e1 := Syscall(SYS_EVENTFD2, uintptr(initval), uintptr(flags), 0)
+	fd = int(r0)
+	if e1 != 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
 func Exit(code int) {
 	Syscall(SYS_EXIT_GROUP, uintptr(code), 0, 0)
 	return
diff --git a/unix/zsyscall_linux_arm.go b/unix/zsyscall_linux_arm.go
index 7601ad5..47d7d53 100644
--- a/unix/zsyscall_linux_arm.go
+++ b/unix/zsyscall_linux_arm.go
@@ -511,6 +511,17 @@
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
+func Eventfd(initval uint, flags int) (fd int, err error) {
+	r0, _, e1 := Syscall(SYS_EVENTFD2, uintptr(initval), uintptr(flags), 0)
+	fd = int(r0)
+	if e1 != 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
 func Exit(code int) {
 	Syscall(SYS_EXIT_GROUP, uintptr(code), 0, 0)
 	return
diff --git a/unix/zsyscall_linux_arm64.go b/unix/zsyscall_linux_arm64.go
index da7a1c6..7bc6693 100644
--- a/unix/zsyscall_linux_arm64.go
+++ b/unix/zsyscall_linux_arm64.go
@@ -511,6 +511,17 @@
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
+func Eventfd(initval uint, flags int) (fd int, err error) {
+	r0, _, e1 := Syscall(SYS_EVENTFD2, uintptr(initval), uintptr(flags), 0)
+	fd = int(r0)
+	if e1 != 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
 func Exit(code int) {
 	Syscall(SYS_EXIT_GROUP, uintptr(code), 0, 0)
 	return
diff --git a/unix/zsyscall_linux_mips.go b/unix/zsyscall_linux_mips.go
index f69db5f..e563565 100644
--- a/unix/zsyscall_linux_mips.go
+++ b/unix/zsyscall_linux_mips.go
@@ -511,6 +511,17 @@
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
+func Eventfd(initval uint, flags int) (fd int, err error) {
+	r0, _, e1 := Syscall(SYS_EVENTFD2, uintptr(initval), uintptr(flags), 0)
+	fd = int(r0)
+	if e1 != 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
 func Exit(code int) {
 	Syscall(SYS_EXIT_GROUP, uintptr(code), 0, 0)
 	return
diff --git a/unix/zsyscall_linux_mips64.go b/unix/zsyscall_linux_mips64.go
index b584866..1ee4a5e 100644
--- a/unix/zsyscall_linux_mips64.go
+++ b/unix/zsyscall_linux_mips64.go
@@ -511,6 +511,17 @@
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
+func Eventfd(initval uint, flags int) (fd int, err error) {
+	r0, _, e1 := Syscall(SYS_EVENTFD2, uintptr(initval), uintptr(flags), 0)
+	fd = int(r0)
+	if e1 != 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
 func Exit(code int) {
 	Syscall(SYS_EXIT_GROUP, uintptr(code), 0, 0)
 	return
diff --git a/unix/zsyscall_linux_mips64le.go b/unix/zsyscall_linux_mips64le.go
index 9031948..80506f5 100644
--- a/unix/zsyscall_linux_mips64le.go
+++ b/unix/zsyscall_linux_mips64le.go
@@ -511,6 +511,17 @@
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
+func Eventfd(initval uint, flags int) (fd int, err error) {
+	r0, _, e1 := Syscall(SYS_EVENTFD2, uintptr(initval), uintptr(flags), 0)
+	fd = int(r0)
+	if e1 != 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
 func Exit(code int) {
 	Syscall(SYS_EXIT_GROUP, uintptr(code), 0, 0)
 	return
diff --git a/unix/zsyscall_linux_mipsle.go b/unix/zsyscall_linux_mipsle.go
index 42c5ab6..0a412e1 100644
--- a/unix/zsyscall_linux_mipsle.go
+++ b/unix/zsyscall_linux_mipsle.go
@@ -511,6 +511,17 @@
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
+func Eventfd(initval uint, flags int) (fd int, err error) {
+	r0, _, e1 := Syscall(SYS_EVENTFD2, uintptr(initval), uintptr(flags), 0)
+	fd = int(r0)
+	if e1 != 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
 func Exit(code int) {
 	Syscall(SYS_EXIT_GROUP, uintptr(code), 0, 0)
 	return
diff --git a/unix/zsyscall_linux_ppc64.go b/unix/zsyscall_linux_ppc64.go
index 8a4cf63..c9751d2 100644
--- a/unix/zsyscall_linux_ppc64.go
+++ b/unix/zsyscall_linux_ppc64.go
@@ -511,6 +511,17 @@
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
+func Eventfd(initval uint, flags int) (fd int, err error) {
+	r0, _, e1 := Syscall(SYS_EVENTFD2, uintptr(initval), uintptr(flags), 0)
+	fd = int(r0)
+	if e1 != 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
 func Exit(code int) {
 	Syscall(SYS_EXIT_GROUP, uintptr(code), 0, 0)
 	return
diff --git a/unix/zsyscall_linux_ppc64le.go b/unix/zsyscall_linux_ppc64le.go
index c7035f2..3848a49 100644
--- a/unix/zsyscall_linux_ppc64le.go
+++ b/unix/zsyscall_linux_ppc64le.go
@@ -511,6 +511,17 @@
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
+func Eventfd(initval uint, flags int) (fd int, err error) {
+	r0, _, e1 := Syscall(SYS_EVENTFD2, uintptr(initval), uintptr(flags), 0)
+	fd = int(r0)
+	if e1 != 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
 func Exit(code int) {
 	Syscall(SYS_EXIT_GROUP, uintptr(code), 0, 0)
 	return
diff --git a/unix/zsyscall_linux_s390x.go b/unix/zsyscall_linux_s390x.go
index 99acf2a..1e16935 100644
--- a/unix/zsyscall_linux_s390x.go
+++ b/unix/zsyscall_linux_s390x.go
@@ -511,6 +511,17 @@
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
+func Eventfd(initval uint, flags int) (fd int, err error) {
+	r0, _, e1 := Syscall(SYS_EVENTFD2, uintptr(initval), uintptr(flags), 0)
+	fd = int(r0)
+	if e1 != 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+// THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
+
 func Exit(code int) {
 	Syscall(SYS_EXIT_GROUP, uintptr(code), 0, 0)
 	return