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authorDean Deng <deandeng@google.com>2020-08-04 18:18:01 -0700
committergVisor bot <gvisor-bot@google.com>2020-08-04 18:20:20 -0700
commitb44408b40e3e8762a77ccf5eeb7f2ef567235c43 (patch)
tree3df8313d5d930a48c6bc1f350ce0bbf342f4a3aa /pkg/refs_vfs2/refs_template.go
parent338f96b36c778748ff27f5ae73cc73b222c5a90e (diff)
Automated rollback of changelist 324906582
PiperOrigin-RevId: 324931854
Diffstat (limited to 'pkg/refs_vfs2/refs_template.go')
-rw-r--r--pkg/refs_vfs2/refs_template.go133
1 files changed, 0 insertions, 133 deletions
diff --git a/pkg/refs_vfs2/refs_template.go b/pkg/refs_vfs2/refs_template.go
deleted file mode 100644
index 3e5b458c7..000000000
--- a/pkg/refs_vfs2/refs_template.go
+++ /dev/null
@@ -1,133 +0,0 @@
-// Copyright 2020 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 refs_template defines a template that can be used by reference counted
-// objects.
-package refs_template
-
-import (
- "runtime"
- "sync/atomic"
-
- "gvisor.dev/gvisor/pkg/log"
- refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
-)
-
-// T is the type of the reference counted object. It is only used to customize
-// debug output when leak checking.
-type T interface{}
-
-// ownerType is used to customize logging. Note that we use a pointer to T so
-// that we do not copy the entire object when passed as a format parameter.
-var ownerType *T
-
-// Refs implements refs.RefCounter. It keeps a reference count using atomic
-// operations and calls the destructor when the count reaches zero.
-//
-// Note that the number of references is actually refCount + 1 so that a default
-// zero-value Refs object contains one reference.
-//
-// +stateify savable
-type Refs struct {
- // refCount is composed of two fields:
- //
- // [32-bit speculative references]:[32-bit real references]
- //
- // Speculative references are used for TryIncRef, to avoid a CompareAndSwap
- // loop. See IncRef, DecRef and TryIncRef for details of how these fields are
- // used.
- refCount int64
-}
-
-func (r *Refs) finalize() {
- var note string
- switch refs_vfs1.GetLeakMode() {
- case refs_vfs1.NoLeakChecking:
- return
- case refs_vfs1.UninitializedLeakChecking:
- note = "(Leak checker uninitialized): "
- }
- if n := r.ReadRefs(); n != 0 {
- log.Warningf("%sAtomicRefCount %p owned by %T garbage collected with ref count of %d (want 0)", note, r, ownerType, n)
- }
-}
-
-// EnableLeakCheck checks for reference leaks when Refs gets garbage collected.
-func (r *Refs) EnableLeakCheck() {
- if refs_vfs1.GetLeakMode() != refs_vfs1.NoLeakChecking {
- runtime.SetFinalizer(r, (*Refs).finalize)
- }
-}
-
-// ReadRefs returns the current number of references. The returned count is
-// inherently racy and is unsafe to use without external synchronization.
-func (r *Refs) ReadRefs() int64 {
- // Account for the internal -1 offset on refcounts.
- return atomic.LoadInt64(&r.refCount) + 1
-}
-
-// IncRef implements refs.RefCounter.IncRef.
-//
-//go:nosplit
-func (r *Refs) IncRef() {
- if v := atomic.AddInt64(&r.refCount, 1); v <= 0 {
- panic("Incrementing non-positive ref count")
- }
-}
-
-// TryIncRef implements refs.RefCounter.TryIncRef.
-//
-// To do this safely without a loop, a speculative reference is first acquired
-// on the object. This allows multiple concurrent TryIncRef calls to distinguish
-// other TryIncRef calls from genuine references held.
-//
-//go:nosplit
-func (r *Refs) TryIncRef() bool {
- const speculativeRef = 1 << 32
- v := atomic.AddInt64(&r.refCount, speculativeRef)
- if int32(v) < 0 {
- // This object has already been freed.
- atomic.AddInt64(&r.refCount, -speculativeRef)
- return false
- }
-
- // Turn into a real reference.
- atomic.AddInt64(&r.refCount, -speculativeRef+1)
- return true
-}
-
-// DecRef implements refs.RefCounter.DecRef.
-//
-// Note that speculative references are counted here. Since they were added
-// prior to real references reaching zero, they will successfully convert to
-// real references. In other words, we see speculative references only in the
-// following case:
-//
-// A: TryIncRef [speculative increase => sees non-negative references]
-// B: DecRef [real decrease]
-// A: TryIncRef [transform speculative to real]
-//
-//go:nosplit
-func (r *Refs) DecRef(destroy func()) {
- switch v := atomic.AddInt64(&r.refCount, -1); {
- case v < -1:
- panic("Decrementing non-positive ref count")
-
- case v == -1:
- // Call the destructor.
- if destroy != nil {
- destroy()
- }
- }
-}