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author | gVisor bot <gvisor-bot@google.com> | 2020-08-05 01:23:10 +0000 |
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committer | gVisor bot <gvisor-bot@google.com> | 2020-08-05 01:23:10 +0000 |
commit | 4fbe1cc8b9fc8d371bbf69a71103a991f07ebe5e (patch) | |
tree | f79ed4c824c107d28037c8bce465b4c661008935 /pkg/sentry/fsimpl/tmpfs/inode_refs.go | |
parent | d064e8d6dfe4785f64f768bda985ce421fa234b7 (diff) | |
parent | b44408b40e3e8762a77ccf5eeb7f2ef567235c43 (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.go | 112 |
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() - } - } -} |