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authorgVisor bot <gvisor-bot@google.com>2020-08-05 01:23:10 +0000
committergVisor bot <gvisor-bot@google.com>2020-08-05 01:23:10 +0000
commit4fbe1cc8b9fc8d371bbf69a71103a991f07ebe5e (patch)
treef79ed4c824c107d28037c8bce465b4c661008935 /pkg/sentry/fsimpl/tmpfs/inode_refs.go
parentd064e8d6dfe4785f64f768bda985ce421fa234b7 (diff)
parentb44408b40e3e8762a77ccf5eeb7f2ef567235c43 (diff)
Merge release-20200622.1-333-gb44408b40 (automated)
Diffstat (limited to 'pkg/sentry/fsimpl/tmpfs/inode_refs.go')
-rw-r--r--pkg/sentry/fsimpl/tmpfs/inode_refs.go112
1 files changed, 0 insertions, 112 deletions
diff --git a/pkg/sentry/fsimpl/tmpfs/inode_refs.go b/pkg/sentry/fsimpl/tmpfs/inode_refs.go
deleted file mode 100644
index 3d3f6ff11..000000000
--- a/pkg/sentry/fsimpl/tmpfs/inode_refs.go
+++ /dev/null
@@ -1,112 +0,0 @@
-package tmpfs
-
-import (
- "sync/atomic"
-
- "gvisor.dev/gvisor/pkg/log"
- refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
- "runtime"
-)
-
-// 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 inodeownerType *inode
-
-// 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 inodeRefs 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 *inodeRefs) 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, inodeownerType, n)
- }
-}
-
-// EnableLeakCheck checks for reference leaks when Refs gets garbage collected.
-func (r *inodeRefs) EnableLeakCheck() {
- if refs_vfs1.GetLeakMode() != refs_vfs1.NoLeakChecking {
- runtime.SetFinalizer(r, (*inodeRefs).finalize)
- }
-}
-
-// ReadRefs returns the current number of references. The returned count is
-// inherently racy and is unsafe to use without external synchronization.
-func (r *inodeRefs) ReadRefs() int64 {
-
- return atomic.LoadInt64(&r.refCount) + 1
-}
-
-// IncRef implements refs.RefCounter.IncRef.
-//
-//go:nosplit
-func (r *inodeRefs) 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 *inodeRefs) TryIncRef() bool {
- const speculativeRef = 1 << 32
- v := atomic.AddInt64(&r.refCount, speculativeRef)
- if int32(v) < 0 {
-
- atomic.AddInt64(&r.refCount, -speculativeRef)
- return false
- }
-
- 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 *inodeRefs) DecRef(destroy func()) {
- switch v := atomic.AddInt64(&r.refCount, -1); {
- case v < -1:
- panic("Decrementing non-positive ref count")
-
- case v == -1:
-
- if destroy != nil {
- destroy()
- }
- }
-}