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// Copyright 2021 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package kernel
import (
"bytes"
"fmt"
"sort"
"strings"
"gvisor.dev/gvisor/pkg/log"
"gvisor.dev/gvisor/pkg/syserror"
)
// EnterInitialCgroups moves t into an initial set of cgroups.
//
// Precondition: t isn't in any cgroups yet, t.cgs is empty.
//
// +checklocksignore parent.mu is conditionally acquired.
func (t *Task) EnterInitialCgroups(parent *Task) {
var inherit map[Cgroup]struct{}
if parent != nil {
parent.mu.Lock()
defer parent.mu.Unlock()
inherit = parent.cgroups
}
joinSet := t.k.cgroupRegistry.computeInitialGroups(inherit)
t.mu.Lock()
defer t.mu.Unlock()
// Transfer ownership of joinSet refs to the task's cgset.
t.cgroups = joinSet
for c, _ := range t.cgroups {
// Since t isn't in any cgroup yet, we can skip the check against
// existing cgroups.
c.Enter(t)
}
}
// EnterCgroup moves t into c.
func (t *Task) EnterCgroup(c Cgroup) error {
newControllers := make(map[CgroupControllerType]struct{})
for _, ctl := range c.Controllers() {
newControllers[ctl.Type()] = struct{}{}
}
t.mu.Lock()
defer t.mu.Unlock()
for oldCG, _ := range t.cgroups {
for _, oldCtl := range oldCG.Controllers() {
if _, ok := newControllers[oldCtl.Type()]; ok {
// Already in a cgroup with the same controller as one of the
// new ones. Requires migration between cgroups.
//
// TODO(b/183137098): Implement cgroup migration.
log.Warningf("Cgroup migration is not implemented")
return syserror.EBUSY
}
}
}
// No migration required.
t.enterCgroupLocked(c)
return nil
}
// +checklocks:t.mu
func (t *Task) enterCgroupLocked(c Cgroup) {
c.IncRef()
t.cgroups[c] = struct{}{}
c.Enter(t)
}
// +checklocks:t.mu
func (t *Task) enterCgroupIfNotYetLocked(c Cgroup) {
if _, ok := t.cgroups[c]; ok {
return
}
t.enterCgroupLocked(c)
}
// LeaveCgroups removes t out from all its cgroups.
func (t *Task) LeaveCgroups() {
t.mu.Lock()
defer t.mu.Unlock()
for c, _ := range t.cgroups {
t.leaveCgroupLocked(c)
}
}
// +checklocks:t.mu
func (t *Task) leaveCgroupLocked(c Cgroup) {
c.Leave(t)
delete(t.cgroups, c)
c.decRef()
}
// taskCgroupEntry represents a line in /proc/<pid>/cgroup, and is used to
// format a cgroup for display.
type taskCgroupEntry struct {
hierarchyID uint32
controllers string
path string
}
// GenerateProcTaskCgroup writes the contents of /proc/<pid>/cgroup for t to buf.
func (t *Task) GenerateProcTaskCgroup(buf *bytes.Buffer) {
t.mu.Lock()
defer t.mu.Unlock()
cgEntries := make([]taskCgroupEntry, 0, len(t.cgroups))
for c, _ := range t.cgroups {
ctls := c.Controllers()
ctlNames := make([]string, 0, len(ctls))
for _, ctl := range ctls {
ctlNames = append(ctlNames, string(ctl.Type()))
}
cgEntries = append(cgEntries, taskCgroupEntry{
// Note: We're guaranteed to have at least one controller, and all
// controllers are guaranteed to be on the same hierarchy.
hierarchyID: ctls[0].HierarchyID(),
controllers: strings.Join(ctlNames, ","),
path: c.Path(),
})
}
sort.Slice(cgEntries, func(i, j int) bool { return cgEntries[i].hierarchyID > cgEntries[j].hierarchyID })
for _, cgE := range cgEntries {
fmt.Fprintf(buf, "%d:%s:%s\n", cgE.hierarchyID, cgE.controllers, cgE.path)
}
}
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