Add handleEINTR() function and use it for read/write/writev syscalls

EINTR is commonly encountered when running under a debugger, so this
change makes it possible to do so without hitting spurious
EINTR errors.

fuse/server.go

@@ -198,6 +198,25 @@ func (ms *Server) DebugData() string {
 // What is a good number?  Maybe the number of CPUs?
 const _MAX_READERS = 2
 
+// handleEINTR retries the given function until it doesn't return syscall.EINTR.
+// This is similar to the HANDLE_EINTR() macro from Chromium ( see
+// https://code.google.com/p/chromium/codesearch#chromium/src/base/posix/eintr_wrapper.h
+// ) and the TEMP_FAILURE_RETRY() from glibc (see
+// https://www.gnu.org/software/libc/manual/html_node/Interrupted-Primitives.html
+// ).
+//
+// Don't use handleEINTR() with syscall.Close(); see
+// https://code.google.com/p/chromium/issues/detail?id=269623 .
+func handleEINTR(fn func() error) (err error) {
+	for {
+		err = fn()
+		if err != syscall.EINTR {
+			break
+		}
+	}
+	return
+}
+
 // Returns a new request, or error. In case exitIdle is given, returns
 // nil, OK if we have too many readers already.
 func (ms *Server) readRequest(exitIdle bool) (req *request, code Status) {
@@ -212,7 +231,12 @@ func (ms *Server) readRequest(exitIdle bool) (req *request, code Status) {
 	ms.reqReaders++
 	ms.reqMu.Unlock()
 
-	n, err := syscall.Read(ms.mountFd, dest)
+	var n int
+	err := handleEINTR(func() error {
+		var err error
+		n, err = syscall.Read(ms.mountFd, dest)
+		return err
+	})
 	if err != nil {
 		code = ToStatus(err)
 		ms.reqPool.Put(req)

fuse/server_darwin.go

@@ -6,7 +6,10 @@ import (
 
 func (ms *Server) systemWrite(req *request, header []byte) Status {
 	if req.flatDataSize() == 0 {
+		err := handleEINTR(func() error {
 			_, err := syscall.Write(ms.mountFd, header)
+			return err
+		})
 		return ToStatus(err)
 	}
 

fuse/server_linux.go

@@ -7,7 +7,10 @@ import (
 
 func (ms *Server) systemWrite(req *request, header []byte) Status {
 	if req.flatDataSize() == 0 {
+		err := handleEINTR(func() error {
 			_, err := syscall.Write(ms.mountFd, header)
+			return err
+		})
 		return ToStatus(err)
 	}
 

fuse/syscall_darwin.go

@@ -9,11 +9,15 @@ import (
 
 // TODO - move these into Go's syscall package.
 
-func sys_writev(fd int, iovecs *syscall.Iovec, cnt int) (n int, errno int) {
+func sys_writev(fd int, iovecs *syscall.Iovec, cnt int) (n int, err error) {
 	n1, _, e1 := syscall.Syscall(
 		syscall.SYS_WRITEV,
 		uintptr(fd), uintptr(unsafe.Pointer(iovecs)), uintptr(cnt))
-	return int(n1), int(e1)
+	n = int(n1)
+	if e1 != 0 {
+		err = syscall.Errno(e1)
+	}
+	return
 }
 
 func writev(fd int, packet [][]byte) (n int, err error) {
@@ -30,9 +34,13 @@ func writev(fd int, packet [][]byte) (n int, err error) {
 		iovecs = append(iovecs, vec)
 	}
 
-	n, errno := sys_writev(fd, &iovecs[0], len(iovecs))
-	if errno != 0 {
-		err = os.NewSyscallError("writev", syscall.Errno(errno))
+	sysErr := handleEINTR(func() error {
+		var err error
+		n, err = sys_writev(fd, &iovecs[0], len(iovecs))
+		return err
+	})
+	if sysErr != nil {
+		err = os.NewSyscallError("writev", sysErr)
 	}
 	return n, err
 }

fuse/syscall_linux.go

@@ -8,11 +8,15 @@ import (
 
 // TODO - move these into Go's syscall package.
 
-func sys_writev(fd int, iovecs *syscall.Iovec, cnt int) (n int, errno int) {
+func sys_writev(fd int, iovecs *syscall.Iovec, cnt int) (n int, err error) {
 	n1, _, e1 := syscall.Syscall(
 		syscall.SYS_WRITEV,
 		uintptr(fd), uintptr(unsafe.Pointer(iovecs)), uintptr(cnt))
-	return int(n1), int(e1)
+	n = int(n1)
+	if e1 != 0 {
+		err = syscall.Errno(e1)
+	}
+	return n, err
 }
 
 func writev(fd int, packet [][]byte) (n int, err error) {
@@ -29,9 +33,13 @@ func writev(fd int, packet [][]byte) (n int, err error) {
 		iovecs = append(iovecs, vec)
 	}
 
-	n, errno := sys_writev(fd, &iovecs[0], len(iovecs))
-	if errno != 0 {
-		err = os.NewSyscallError("writev", syscall.Errno(errno))
+	sysErr := handleEINTR(func() error {
+		var err error
+		n, err = sys_writev(fd, &iovecs[0], len(iovecs))
+		return err
+	})
+	if sysErr != nil {
+		err = os.NewSyscallError("writev", sysErr)
 	}
 	return n, err
 }