From 1c0535297067179a822ba2dd9a6fe13a8be5a666 Mon Sep 17 00:00:00 2001 From: Jamie Liu Date: Fri, 13 Mar 2020 13:17:59 -0700 Subject: Fix oom_score_adj. - Make oomScoreAdj a ThreadGroup field (Linux: signal_struct::oom_score_adj). - Avoid deadlock caused by Task.OOMScoreAdj()/SetOOMScoreAdj() locking Task.mu and TaskSet.mu in the wrong order (via Task.ExitState()). PiperOrigin-RevId: 300814698 --- pkg/sentry/fs/proc/task.go | 17 ++++++++++------- pkg/sentry/fsimpl/proc/task_files.go | 10 ++++++---- pkg/sentry/kernel/task.go | 29 ++++++----------------------- pkg/sentry/kernel/task_clone.go | 9 +++------ pkg/sentry/kernel/task_start.go | 4 ---- pkg/sentry/kernel/thread_group.go | 7 +++++++ 6 files changed, 32 insertions(+), 44 deletions(-) (limited to 'pkg') diff --git a/pkg/sentry/fs/proc/task.go b/pkg/sentry/fs/proc/task.go index 03cc788c8..d6c5dd2c1 100644 --- a/pkg/sentry/fs/proc/task.go +++ b/pkg/sentry/fs/proc/task.go @@ -853,15 +853,15 @@ func (o *oomScoreAdj) GetFile(ctx context.Context, dirent *fs.Dirent, flags fs.F // Read implements fs.FileOperations.Read. func (f *oomScoreAdjFile) Read(ctx context.Context, _ *fs.File, dst usermem.IOSequence, offset int64) (int64, error) { - if offset != 0 { - return 0, io.EOF + if f.t.ExitState() == kernel.TaskExitDead { + return 0, syserror.ESRCH } - adj, err := f.t.OOMScoreAdj() - if err != nil { - return 0, err + var buf bytes.Buffer + fmt.Fprintf(&buf, "%d\n", f.t.OOMScoreAdj()) + if offset >= int64(buf.Len()) { + return 0, io.EOF } - adjBytes := []byte(strconv.FormatInt(int64(adj), 10) + "\n") - n, err := dst.CopyOut(ctx, adjBytes) + n, err := dst.CopyOut(ctx, buf.Bytes()[offset:]) return int64(n), err } @@ -880,6 +880,9 @@ func (f *oomScoreAdjFile) Write(ctx context.Context, _ *fs.File, src usermem.IOS return 0, err } + if f.t.ExitState() == kernel.TaskExitDead { + return 0, syserror.ESRCH + } if err := f.t.SetOOMScoreAdj(v); err != nil { return 0, err } diff --git a/pkg/sentry/fsimpl/proc/task_files.go b/pkg/sentry/fsimpl/proc/task_files.go index 5a231ac86..4d3332771 100644 --- a/pkg/sentry/fsimpl/proc/task_files.go +++ b/pkg/sentry/fsimpl/proc/task_files.go @@ -539,11 +539,10 @@ var _ vfs.WritableDynamicBytesSource = (*oomScoreAdj)(nil) // Generate implements vfs.DynamicBytesSource.Generate. func (o *oomScoreAdj) Generate(ctx context.Context, buf *bytes.Buffer) error { - adj, err := o.task.OOMScoreAdj() - if err != nil { - return err + if o.task.ExitState() == kernel.TaskExitDead { + return syserror.ESRCH } - fmt.Fprintf(buf, "%d\n", adj) + fmt.Fprintf(buf, "%d\n", o.task.OOMScoreAdj()) return nil } @@ -562,6 +561,9 @@ func (o *oomScoreAdj) Write(ctx context.Context, src usermem.IOSequence, offset return 0, err } + if o.task.ExitState() == kernel.TaskExitDead { + return 0, syserror.ESRCH + } if err := o.task.SetOOMScoreAdj(v); err != nil { return 0, err } diff --git a/pkg/sentry/kernel/task.go b/pkg/sentry/kernel/task.go index c0dbbe890..8452ddf5b 100644 --- a/pkg/sentry/kernel/task.go +++ b/pkg/sentry/kernel/task.go @@ -555,13 +555,6 @@ type Task struct { // // startTime is protected by mu. startTime ktime.Time - - // oomScoreAdj is the task's OOM score adjustment. This is currently not - // used but is maintained for consistency. - // TODO(gvisor.dev/issue/1967) - // - // oomScoreAdj is protected by mu, and is owned by the task goroutine. - oomScoreAdj int32 } func (t *Task) savePtraceTracer() *Task { @@ -856,27 +849,17 @@ func (t *Task) ContainerID() string { return t.containerID } -// OOMScoreAdj gets the task's OOM score adjustment. -func (t *Task) OOMScoreAdj() (int32, error) { - t.mu.Lock() - defer t.mu.Unlock() - if t.ExitState() == TaskExitDead { - return 0, syserror.ESRCH - } - return t.oomScoreAdj, nil +// OOMScoreAdj gets the task's thread group's OOM score adjustment. +func (t *Task) OOMScoreAdj() int32 { + return atomic.LoadInt32(&t.tg.oomScoreAdj) } -// SetOOMScoreAdj sets the task's OOM score adjustment. The value should be -// between -1000 and 1000 inclusive. +// SetOOMScoreAdj sets the task's thread group's OOM score adjustment. The +// value should be between -1000 and 1000 inclusive. func (t *Task) SetOOMScoreAdj(adj int32) error { - t.mu.Lock() - defer t.mu.Unlock() - if t.ExitState() == TaskExitDead { - return syserror.ESRCH - } if adj > 1000 || adj < -1000 { return syserror.EINVAL } - t.oomScoreAdj = adj + atomic.StoreInt32(&t.tg.oomScoreAdj, adj) return nil } diff --git a/pkg/sentry/kernel/task_clone.go b/pkg/sentry/kernel/task_clone.go index dda502bb8..e1ecca99e 100644 --- a/pkg/sentry/kernel/task_clone.go +++ b/pkg/sentry/kernel/task_clone.go @@ -15,6 +15,8 @@ package kernel import ( + "sync/atomic" + "gvisor.dev/gvisor/pkg/abi/linux" "gvisor.dev/gvisor/pkg/bpf" "gvisor.dev/gvisor/pkg/sentry/inet" @@ -260,15 +262,11 @@ func (t *Task) Clone(opts *CloneOptions) (ThreadID, *SyscallControl, error) { sh = sh.Fork() } tg = t.k.NewThreadGroup(tg.mounts, pidns, sh, opts.TerminationSignal, tg.limits.GetCopy()) + tg.oomScoreAdj = atomic.LoadInt32(&t.tg.oomScoreAdj) rseqAddr = t.rseqAddr rseqSignature = t.rseqSignature } - adj, err := t.OOMScoreAdj() - if err != nil { - return 0, nil, err - } - cfg := &TaskConfig{ Kernel: t.k, ThreadGroup: tg, @@ -287,7 +285,6 @@ func (t *Task) Clone(opts *CloneOptions) (ThreadID, *SyscallControl, error) { RSeqAddr: rseqAddr, RSeqSignature: rseqSignature, ContainerID: t.ContainerID(), - OOMScoreAdj: adj, } if opts.NewThreadGroup { cfg.Parent = t diff --git a/pkg/sentry/kernel/task_start.go b/pkg/sentry/kernel/task_start.go index 2bbf48bb8..a5035bb7f 100644 --- a/pkg/sentry/kernel/task_start.go +++ b/pkg/sentry/kernel/task_start.go @@ -93,9 +93,6 @@ type TaskConfig struct { // ContainerID is the container the new task belongs to. ContainerID string - - // oomScoreAdj is the task's OOM score adjustment. - OOMScoreAdj int32 } // NewTask creates a new task defined by cfg. @@ -146,7 +143,6 @@ func (ts *TaskSet) newTask(cfg *TaskConfig) (*Task, error) { rseqSignature: cfg.RSeqSignature, futexWaiter: futex.NewWaiter(), containerID: cfg.ContainerID, - oomScoreAdj: cfg.OOMScoreAdj, } t.creds.Store(cfg.Credentials) t.endStopCond.L = &t.tg.signalHandlers.mu diff --git a/pkg/sentry/kernel/thread_group.go b/pkg/sentry/kernel/thread_group.go index 268f62e9d..52849f5b3 100644 --- a/pkg/sentry/kernel/thread_group.go +++ b/pkg/sentry/kernel/thread_group.go @@ -254,6 +254,13 @@ type ThreadGroup struct { // // tty is protected by the signal mutex. tty *TTY + + // oomScoreAdj is the thread group's OOM score adjustment. This is + // currently not used but is maintained for consistency. + // TODO(gvisor.dev/issue/1967) + // + // oomScoreAdj is accessed using atomic memory operations. + oomScoreAdj int32 } // NewThreadGroup returns a new, empty thread group in PID namespace pidns. The -- cgit v1.2.3