Merge pull request #2258 from masters-of-cats/eintr-retry

Retry writing to cgroup files on EINTR error

libcontainer/cgroups/fscommon/fscommon.go

@@ -4,9 +4,12 @@ package fscommon
 
 import (
 	"io/ioutil"
+	"os"
+	"syscall"
 
 	securejoin "github.com/cyphar/filepath-securejoin"
 	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
 )
 
 func WriteFile(dir, file, data string) error {
@@ -17,7 +20,7 @@ func WriteFile(dir, file, data string) error {
 	if err != nil {
 		return err
 	}
-	if err := ioutil.WriteFile(path, []byte(data), 0700); err != nil {
+	if err := retryingWriteFile(path, []byte(data), 0700); err != nil {
 		return errors.Wrapf(err, "failed to write %q to %q", data, path)
 	}
 	return nil
@@ -34,3 +37,24 @@ func ReadFile(dir, file string) (string, error) {
 	data, err := ioutil.ReadFile(path)
 	return string(data), err
 }
+
+func retryingWriteFile(filename string, data []byte, perm os.FileMode) error {
+	for {
+		err := ioutil.WriteFile(filename, data, perm)
+		if isInterruptedWriteFile(err) {
+			logrus.Infof("interrupted while writing %s to %s", string(data), filename)
+			continue
+		}
+		return err
+	}
+}
+
+func isInterruptedWriteFile(err error) bool {
+	if patherr, ok := err.(*os.PathError); ok {
+		errno, ok2 := patherr.Err.(syscall.Errno)
+		if ok2 && errno == syscall.EINTR {
+			return true
+		}
+	}
+	return false
+}

libcontainer/cgroups/fscommon/fscommon_test.go

@@ -0,0 +1,39 @@
+// +build linux
+
+package fscommon
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"strconv"
+	"testing"
+	"time"
+
+	"github.com/opencontainers/runc/libcontainer/cgroups"
+)
+
+func TestWriteCgroupFileHandlesInterrupt(t *testing.T) {
+	if cgroups.IsCgroup2UnifiedMode() {
+		t.Skip("cgroup v2 is not supported")
+	}
+
+	memoryCgroupMount, err := cgroups.FindCgroupMountpoint("", "memory")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cgroupName := fmt.Sprintf("test-eint-%d", time.Now().Nanosecond())
+	cgroupPath := filepath.Join(memoryCgroupMount, cgroupName)
+	if err := os.MkdirAll(cgroupPath, 0755); err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(cgroupPath)
+
+	for i := 0; i < 100000; i++ {
+		limit := 1024*1024 + i
+		if err := WriteFile(cgroupPath, "memory.limit_in_bytes", strconv.Itoa(limit)); err != nil {
+			t.Fatalf("Failed to write %d on attempt %d: %+v", limit, i, err)
+		}
+	}
+}