From 4e65e0e90a588489be02b3c70981f95eb12e0413 Mon Sep 17 00:00:00 2001
From: Shishir Mahajan <shishir.mahajan@redhat.com>
Date: Fri, 20 Mar 2015 15:29:14 -0400
Subject: [PATCH] Throw an error if cgroup tries to set cpu-shares more/less
 than the maximum/minimum permissible value.

Signed-off-by: Shishir Mahajan <shishir.mahajan@redhat.com>
---
 cgroups/fs/apply_raw.go          | 28 ++++++++++++++++++++++++++++
 cgroups/systemd/apply_systemd.go | 24 ++++++++++++++++++++++++
 2 files changed, 52 insertions(+)

diff --git a/cgroups/fs/apply_raw.go b/cgroups/fs/apply_raw.go
index 0a2d76bcd4e..5bfa7985e8e 100644
--- a/cgroups/fs/apply_raw.go
+++ b/cgroups/fs/apply_raw.go
@@ -1,8 +1,11 @@
 package fs
 
 import (
+	"fmt"
+	"io"
 	"io/ioutil"
 	"os"
+	"path"
 	"path/filepath"
 	"strconv"
 	"sync"
@@ -75,10 +78,13 @@ type data struct {
 }
 
 func (m *Manager) Apply(pid int) error {
+
 	if m.Cgroups == nil {
 		return nil
 	}
 
+	var c = m.Cgroups
+
 	d, err := getCgroupData(m.Cgroups, pid)
 	if err != nil {
 		return err
@@ -108,6 +114,28 @@ func (m *Manager) Apply(pid int) error {
 	}
 	m.Paths = paths
 
+	var cpuShares int64
+
+	fd, err := os.Open(path.Join(m.Paths["cpu"], "cpu.shares"))
+	if err != nil {
+		return err
+	}
+
+	_, err = fmt.Fscanf(fd, "%d", &cpuShares)
+	if err != nil && err != io.EOF {
+		return err
+	}
+
+	fd.Close()
+
+	if c.CpuShares != 0 {
+		if c.CpuShares > cpuShares {
+			return fmt.Errorf("The maximum allowed cpu-shares is %d", cpuShares)
+		} else if c.CpuShares < cpuShares {
+			return fmt.Errorf("The minimum allowed cpu-shares is %d", cpuShares)
+		}
+	}
+
 	return nil
 }
 
diff --git a/cgroups/systemd/apply_systemd.go b/cgroups/systemd/apply_systemd.go
index 85ee5db06d3..10a32d432fe 100644
--- a/cgroups/systemd/apply_systemd.go
+++ b/cgroups/systemd/apply_systemd.go
@@ -5,8 +5,10 @@ package systemd
 import (
 	"bytes"
 	"fmt"
+	"io"
 	"io/ioutil"
 	"os"
+	"path"
 	"path/filepath"
 	"strconv"
 	"strings"
@@ -241,6 +243,28 @@ func (m *Manager) Apply(pid int) error {
 
 	m.Paths = paths
 
+	var cpuShares int64
+
+	fd, err := os.Open(path.Join(m.Paths["cpu"], "cpu.shares"))
+	if err != nil {
+		return err
+	}
+
+	_, err = fmt.Fscanf(fd, "%d", &cpuShares)
+	if err != nil && err != io.EOF {
+		return err
+	}
+
+	fd.Close()
+
+	if c.CpuShares != 0 {
+		if c.CpuShares > cpuShares {
+			return fmt.Errorf("The maximum allowed cpu-shares is %d", cpuShares)
+		} else if c.CpuShares < cpuShares {
+			return fmt.Errorf("The minimum allowed cpu-shares is %d", cpuShares)
+		}
+	}
+
 	return nil
 }