lock

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 Go to latest Published: Dec 17, 2024 License: Apache-2.0, MIT Imports: 11 Imported by: 8

Documentation

Overview

Package lock is the API for POSIX-style advisory regional file locks and BSD-style full file locks.

Callers needing to enforce these types of locks, like sys_fcntl, can call LockRegion and UnlockRegion on a thread-safe set of Locks. Locks are specific to a unique file (unique device/inode pair) and for this reason should not be shared between files.

A Lock has a set of holders identified by UniqueID. Normally this is the pid of the thread attempting to acquire the lock.

Since these are advisory locks, they do not need to be integrated into Reads/Writes and for this reason there is no way to *check* if a lock is held. One can only attempt to take a lock or unlock an existing lock.

A Lock in a set of Locks is typed: it is either a read lock with any number of readers and no writer, or a write lock with no readers.

As expected from POSIX, any attempt to acquire a write lock on a file region when there already exits a write lock held by a different uid will fail. Any attempt to acquire a write lock on a file region when there is more than one reader will fail. Any attempt to acquire a read lock on a file region when there is already a writer will fail.

In special cases, a read lock may be upgraded to a write lock and a write lock can be downgraded to a read lock. This can only happen if:

  • read lock upgrade to write lock: There can be only one reader and the reader must be the same as the requested write lock holder.

  • write lock downgrade to read lock: The writer must be the same as the requested read lock holder.

UnlockRegion always succeeds. If LockRegion fails the caller should normally interpret this as "try again later".

Index

Constants

View Source 
const (
	// minDegree is the minimum degree of an internal node in a Set B-tree.
	//
	//	- Any non-root node has at least minDegree-1 segments.
	//
	//	- Any non-root internal (non-leaf) node has at least minDegree children.
	//
	//	- The root node may have fewer than minDegree-1 segments, but it may
	// only have 0 segments if the tree is empty.
	//
	// Our implementation requires minDegree >= 3. Higher values of minDegree
	// usually improve performance, but increase memory usage for small sets.
	LockminDegree = 3

	LockmaxDegree = 2 * LockminDegree
)
View Source 
const LockEOF = math.MaxInt64

LockEOF is the maximal possible end of a regional file lock.

A BSD-style full file lock can be represented as a regional file lock from offset 0 to LockEOF.

View Source 
const LocktrackGaps = 0

trackGaps is an optional parameter.

If trackGaps is 1, the Set will track maximum gap size recursively, enabling the GapIterator.{Prev,Next}LargeEnoughGap functions. In this case, Key must be an unsigned integer.

trackGaps must be 0 or 1.

Variables

This section is empty.

Functions

func LockzeroNodeSlice 

func LockzeroNodeSlice(slice []*Locknode)

func LockzeroValueSlice 

func LockzeroValueSlice(slice []Lock)

Types

type Lock 

type Lock struct {
	// Readers are the set of read lock holders identified by UniqueID.
	// If len(Readers) > 0 then Writer must be nil.
	Readers map[UniqueID]OwnerInfo

	// Writer holds the writer unique ID. It's nil if there are no writers.
	Writer UniqueID

	// WriterInfo describes the writer. It is only meaningful if Writer != nil.
	WriterInfo OwnerInfo
}

Lock is a regional file lock. It consists of either a single writer or a set of readers.

A Lock may be upgraded from a read lock to a write lock only if there is a single reader and that reader has the same uid as the write lock.

A Lock may be downgraded from a write lock to a read lock only if the write lock's uid is the same as the read lock.

Accesses to Lock are synchronized through the Locks object to which it belongs.

+stateify savable

func (*Lock) StateFields 

func (l *Lock) StateFields() []string

func (*Lock) StateLoad 

func (l *Lock) StateLoad(ctx context.Context, stateSourceObject state.Source)

+checklocksignore

func (*Lock) StateSave 

func (l *Lock) StateSave(stateSinkObject state.Sink)

+checklocksignore

func (*Lock) StateTypeName 

func (l *Lock) StateTypeName() string

type LockFlatSegment 

type LockFlatSegment struct {
	Start uint64
	End   uint64
	Value Lock
}

FlatSegment represents a segment as a single object. FlatSegment is used as an intermediate representation for save/restore and tests.

+stateify savable

func (*LockFlatSegment) StateFields 

func (l *LockFlatSegment) StateFields() []string

func (*LockFlatSegment) StateLoad 

func (l *LockFlatSegment) StateLoad(ctx context.Context, stateSourceObject state.Source)

+checklocksignore

func (*LockFlatSegment) StateSave 

func (l *LockFlatSegment) StateSave(stateSinkObject state.Sink)

+checklocksignore

func (*LockFlatSegment) StateTypeName 

func (l *LockFlatSegment) StateTypeName() string

type LockGapIterator 

type LockGapIterator struct {
	// contains filtered or unexported fields
}

A GapIterator is conceptually one of:

  • A pointer to a position between two segments, before the first segment, or after the last segment in a set, called a *gap*; or

  • A terminal iterator, which is a sentinel indicating that the end of iteration has been reached.

Note that the gap between two adjacent segments exists (iterators to it are non-terminal), but has a length of zero. GapIterator.IsEmpty returns true for such gaps. An empty set contains a single gap, spanning the entire range of the set's keys.

GapIterators are copyable values and are meaningfully equality-comparable. The zero value of GapIterator is a terminal iterator.

Unless otherwise specified, any mutation of a set invalidates all existing iterators into the set.

func (LockGapIterator) End 

func (gap LockGapIterator) End() uint64

End is equivalent to Range().End, but should be preferred if only the end of the range is needed.

func (LockGapIterator) IsEmpty 

func (gap LockGapIterator) IsEmpty() bool

IsEmpty returns true if the iterated gap is empty (that is, the "gap" is between two adjacent segments.)

func (LockGapIterator) NextGap 

func (gap LockGapIterator) NextGap() LockGapIterator

NextGap returns the iterated gap's successor. If no such gap exists, NextGap returns a terminal iterator.

func (LockGapIterator) NextLargeEnoughGap 

func (gap LockGapIterator) NextLargeEnoughGap(minSize uint64) LockGapIterator

NextLargeEnoughGap returns the iterated gap's first next gap with larger length than minSize. If not found, return a terminal gap iterator (does NOT include this gap itself).

Precondition: trackGaps must be 1.

func (LockGapIterator) NextSegment 

func (gap LockGapIterator) NextSegment() LockIterator

NextSegment returns the segment immediately after the iterated gap. If no such segment exists, NextSegment returns a terminal iterator.

func (LockGapIterator) Ok 

func (gap LockGapIterator) Ok() bool

Ok returns true if the iterator is not terminal. All other methods are only valid for non-terminal iterators.

func (LockGapIterator) PrevGap 

func (gap LockGapIterator) PrevGap() LockGapIterator

PrevGap returns the iterated gap's predecessor. If no such gap exists, PrevGap returns a terminal iterator.

func (LockGapIterator) PrevLargeEnoughGap 

func (gap LockGapIterator) PrevLargeEnoughGap(minSize uint64) LockGapIterator

PrevLargeEnoughGap returns the iterated gap's first prev gap with larger or equal length than minSize. If not found, return a terminal gap iterator (does NOT include this gap itself).

Precondition: trackGaps must be 1.

func (LockGapIterator) PrevSegment 

func (gap LockGapIterator) PrevSegment() LockIterator

PrevSegment returns the segment immediately before the iterated gap. If no such segment exists, PrevSegment returns a terminal iterator.

func (LockGapIterator) Range 

func (gap LockGapIterator) Range() LockRange

Range returns the range spanned by the iterated gap.

func (LockGapIterator) Start 

func (gap LockGapIterator) Start() uint64

Start is equivalent to Range().Start, but should be preferred if only the start of the range is needed.

type LockIterator 

type LockIterator struct {
	// contains filtered or unexported fields
}

A Iterator is conceptually one of:

  • A pointer to a segment in a set; or

  • A terminal iterator, which is a sentinel indicating that the end of iteration has been reached.

Iterators are copyable values and are meaningfully equality-comparable. The zero value of Iterator is a terminal iterator.

Unless otherwise specified, any mutation of a set invalidates all existing iterators into the set.

func LocksegmentAfterPosition 

func LocksegmentAfterPosition(n *Locknode, i int) LockIterator

segmentAfterPosition returns the successor segment of the position given by n.children[i], which may or may not contain a child. If no such segment exists, segmentAfterPosition returns a terminal iterator.

func LocksegmentBeforePosition 

func LocksegmentBeforePosition(n *Locknode, i int) LockIterator

segmentBeforePosition returns the predecessor segment of the position given by n.children[i], which may or may not contain a child. If no such segment exists, segmentBeforePosition returns a terminal iterator.

func (LockIterator) End 

func (seg LockIterator) End() uint64

End is equivalent to Range().End, but should be preferred if only the end of the range is needed.

func (LockIterator) NextGap 

func (seg LockIterator) NextGap() LockGapIterator

NextGap returns the gap immediately after the iterated segment.

func (LockIterator) NextNonEmpty 

func (seg LockIterator) NextNonEmpty() (LockIterator, LockGapIterator)

NextNonEmpty returns the iterated segment's successor if it is adjacent, or the gap after the iterated segment otherwise. If seg.End() == Functions.MaxKey(), NextNonEmpty will return two terminal iterators. Otherwise, exactly one of the iterators returned by NextNonEmpty will be non-terminal.

func (LockIterator) NextSegment 

func (seg LockIterator) NextSegment() LockIterator

NextSegment returns the iterated segment's successor. If there is no succeeding segment, NextSegment returns a terminal iterator.

func (LockIterator) Ok 

func (seg LockIterator) Ok() bool

Ok returns true if the iterator is not terminal. All other methods are only valid for non-terminal iterators.

func (LockIterator) PrevGap 

func (seg LockIterator) PrevGap() LockGapIterator

PrevGap returns the gap immediately before the iterated segment.

func (LockIterator) PrevNonEmpty 

func (seg LockIterator) PrevNonEmpty() (LockIterator, LockGapIterator)

PrevNonEmpty returns the iterated segment's predecessor if it is adjacent, or the gap before the iterated segment otherwise. If seg.Start() == Functions.MinKey(), PrevNonEmpty will return two terminal iterators. Otherwise, exactly one of the iterators returned by PrevNonEmpty will be non-terminal.

func (LockIterator) PrevSegment 

func (seg LockIterator) PrevSegment() LockIterator

PrevSegment returns the iterated segment's predecessor. If there is no preceding segment, PrevSegment returns a terminal iterator.

func (LockIterator) Range 

func (seg LockIterator) Range() LockRange

Range returns the iterated segment's range key.

func (LockIterator) SetEnd 

func (seg LockIterator) SetEnd(end uint64)

SetEnd mutates the iterated segment's end. If the new end value would cause the iterated segment to overlap another segment, or would result in an invalid range, SetEnd panics. This operation does not invalidate any iterators.

func (LockIterator) SetEndUnchecked 

func (seg LockIterator) SetEndUnchecked(end uint64)

SetEndUnchecked mutates the iterated segment's end. This operation does not invalidate any iterators.

Preconditions: The new end must be valid:

  • end > seg.Start().
  • If seg.NextSegment().Ok(), then end <= seg.NextSegment().Start().

func (LockIterator) SetRange 

func (seg LockIterator) SetRange(r LockRange)

SetRange mutates the iterated segment's range key. If the new range would cause the iterated segment to overlap another segment, or if the new range is invalid, SetRange panics. This operation does not invalidate any iterators.

func (LockIterator) SetRangeUnchecked 

func (seg LockIterator) SetRangeUnchecked(r LockRange)

SetRangeUnchecked mutates the iterated segment's range key. This operation does not invalidate any iterators.

Preconditions: - r.Length() > 0. - The new range must not overlap an existing one:

  • If seg.NextSegment().Ok(), then r.end <= seg.NextSegment().Start().
  • If seg.PrevSegment().Ok(), then r.start >= seg.PrevSegment().End().

func (LockIterator) SetStart 

func (seg LockIterator) SetStart(start uint64)

SetStart mutates the iterated segment's start. If the new start value would cause the iterated segment to overlap another segment, or would result in an invalid range, SetStart panics. This operation does not invalidate any iterators.

func (LockIterator) SetStartUnchecked 

func (seg LockIterator) SetStartUnchecked(start uint64)

SetStartUnchecked mutates the iterated segment's start. This operation does not invalidate any iterators.

Preconditions: The new start must be valid:

  • start < seg.End()
  • If seg.PrevSegment().Ok(), then start >= seg.PrevSegment().End().

func (LockIterator) SetValue 

func (seg LockIterator) SetValue(val Lock)

SetValue mutates the iterated segment's value. This operation does not invalidate any iterators.

func (LockIterator) Start 

func (seg LockIterator) Start() uint64

Start is equivalent to Range().Start, but should be preferred if only the start of the range is needed.

func (LockIterator) Value 

func (seg LockIterator) Value() Lock

Value returns a copy of the iterated segment's value.

func (LockIterator) ValuePtr 

func (seg LockIterator) ValuePtr() *Lock

ValuePtr returns a pointer to the iterated segment's value. The pointer is invalidated if the iterator is invalidated. This operation does not invalidate any iterators.

type LockRange 

type LockRange struct {
	// Start is the inclusive start of the range.
	Start uint64

	// End is the exclusive end of the range.
	End uint64
}

A Range represents a contiguous range of T.

+stateify savable

func ComputeRange 

func ComputeRange(start, length, offset int64) (LockRange, error)

ComputeRange takes a positive file offset and computes the start of a LockRange using start (relative to offset) and the end of the LockRange using length. The values of start and length may be negative but the resulting LockRange must preserve that LockRange.Start < LockRange.End and LockRange.Start > 0.

func (LockRange) CanSplitAt 

func (r LockRange) CanSplitAt(x uint64) bool

CanSplitAt returns true if it is legal to split a segment spanning the range r at x; that is, splitting at x would produce two ranges, both of which have non-zero length.

func (LockRange) Contains 

func (r LockRange) Contains(x uint64) bool

Contains returns true if r contains x.

func (LockRange) Intersect 

func (r LockRange) Intersect(r2 LockRange) LockRange

Intersect returns a range consisting of the intersection between r and r2. If r and r2 do not overlap, Intersect returns a range with unspecified bounds, but for which Length() == 0.

func (LockRange) IsSupersetOf 

func (r LockRange) IsSupersetOf(r2 LockRange) bool

IsSupersetOf returns true if r is a superset of r2; that is, the range r2 is contained within r.

func (LockRange) Length 

func (r LockRange) Length() uint64

Length returns the length of the range.

func (LockRange) Overlaps 

func (r LockRange) Overlaps(r2 LockRange) bool

Overlaps returns true if r and r2 overlap.

func (*LockRange) StateFields 

func (r *LockRange) StateFields() []string

func (*LockRange) StateLoad 

func (r *LockRange) StateLoad(ctx context.Context, stateSourceObject state.Source)

+checklocksignore

func (*LockRange) StateSave 

func (r *LockRange) StateSave(stateSinkObject state.Sink)

+checklocksignore

func (*LockRange) StateTypeName 

func (r *LockRange) StateTypeName() string

func (LockRange) WellFormed 

func (r LockRange) WellFormed() bool

WellFormed returns true if r.Start <= r.End. All other methods on a Range require that the Range is well-formed.

type LockSet 

type LockSet struct {
	// contains filtered or unexported fields
}

A Set is a mapping of segments with non-overlapping Range keys. The zero value for a Set is an empty set. Set values are not safely movable nor copyable. Set is thread-compatible.

+stateify savable

func (*LockSet) ExportSlice 

func (s *LockSet) ExportSlice() []LockFlatSegment

ExportSlice returns a copy of all segments in the given set, in ascending key order.

func (*LockSet) Find 

func (s *LockSet) Find(key uint64) (LockIterator, LockGapIterator)

Find returns the segment or gap whose range contains the given key. If a segment is found, the returned Iterator is non-terminal and the returned GapIterator is terminal. Otherwise, the returned Iterator is terminal and the returned GapIterator is non-terminal.

func (*LockSet) FindGap 

func (s *LockSet) FindGap(key uint64) LockGapIterator

FindGap returns the gap containing the given key. If no such gap exists (i.e. the set contains a segment containing that key), FindGap returns a terminal iterator.

func (*LockSet) FindSegment 

func (s *LockSet) FindSegment(key uint64) LockIterator

FindSegment returns the segment whose range contains the given key. If no such segment exists, FindSegment returns a terminal iterator.

func (*LockSet) FirstGap 

func (s *LockSet) FirstGap() LockGapIterator

FirstGap returns the first gap in the set.

func (*LockSet) FirstLargeEnoughGap 

func (s *LockSet) FirstLargeEnoughGap(minSize uint64) LockGapIterator

FirstLargeEnoughGap returns the first gap in the set with at least the given length. If no such gap exists, FirstLargeEnoughGap returns a terminal iterator.

Precondition: trackGaps must be 1.

func (*LockSet) FirstSegment 

func (s *LockSet) FirstSegment() LockIterator

FirstSegment returns the first segment in the set. If the set is empty, FirstSegment returns a terminal iterator.

func (*LockSet) ImportSlice 

func (s *LockSet) ImportSlice(fs []LockFlatSegment) error

ImportSlice initializes the given set from the given slice.

Preconditions:

  • s must be empty.
  • fs must represent a valid set (the segments in fs must have valid lengths that do not overlap).
  • The segments in fs must be sorted in ascending key order.

func (*LockSet) Insert 

func (s *LockSet) Insert(gap LockGapIterator, r LockRange, val Lock) LockIterator

Insert inserts the given segment into the given gap. If the new segment can be merged with adjacent segments, Insert will do so. Insert returns an iterator to the segment containing the inserted value (which may have been merged with other values). All existing iterators (including gap, but not including the returned iterator) are invalidated.

If the gap cannot accommodate the segment, or if r is invalid, Insert panics.

Insert is semantically equivalent to a InsertWithoutMerging followed by a Merge, but may be more efficient. Note that there is no unchecked variant of Insert since Insert must retrieve and inspect gap's predecessor and successor segments regardless.

func (*LockSet) InsertRange 

func (s *LockSet) InsertRange(r LockRange, val Lock) LockIterator

InsertRange inserts the given segment into the set. If the new segment can be merged with adjacent segments, InsertRange will do so. InsertRange returns an iterator to the segment containing the inserted value (which may have been merged with other values). All existing iterators (excluding the returned iterator) are invalidated.

If the new segment would overlap an existing segment, or if r is invalid, InsertRange panics.

InsertRange searches the set to find the gap to insert into. If the caller already has the appropriate GapIterator, or if the caller needs to do additional work between finding the gap and insertion, use Insert instead.

func (*LockSet) InsertWithoutMerging 

func (s *LockSet) InsertWithoutMerging(gap LockGapIterator, r LockRange, val Lock) LockIterator

InsertWithoutMerging inserts the given segment into the given gap and returns an iterator to the inserted segment. All existing iterators (including gap, but not including the returned iterator) are invalidated.

If the gap cannot accommodate the segment, or if r is invalid, InsertWithoutMerging panics.

func (*LockSet) InsertWithoutMergingRange 

func (s *LockSet) InsertWithoutMergingRange(r LockRange, val Lock) LockIterator

InsertWithoutMergingRange inserts the given segment into the set and returns an iterator to the inserted segment. All existing iterators (excluding the returned iterator) are invalidated.

If the new segment would overlap an existing segment, or if r is invalid, InsertWithoutMergingRange panics.

InsertWithoutMergingRange searches the set to find the gap to insert into. If the caller already has the appropriate GapIterator, or if the caller needs to do additional work between finding the gap and insertion, use InsertWithoutMerging instead.

func (*LockSet) InsertWithoutMergingUnchecked 

func (s *LockSet) InsertWithoutMergingUnchecked(gap LockGapIterator, r LockRange, val Lock) LockIterator

InsertWithoutMergingUnchecked inserts the given segment into the given gap and returns an iterator to the inserted segment. All existing iterators (including gap, but not including the returned iterator) are invalidated.

Preconditions:

  • r.Start >= gap.Start().
  • r.End <= gap.End().

func (*LockSet) IsEmpty 

func (s *LockSet) IsEmpty() bool

IsEmpty returns true if the set contains no segments.

func (*LockSet) IsEmptyRange 

func (s *LockSet) IsEmptyRange(r LockRange) bool

IsEmptyRange returns true iff no segments in the set overlap the given range. This is semantically equivalent to s.SpanRange(r) == 0, but may be more efficient.

func (*LockSet) Isolate 

func (s *LockSet) Isolate(seg LockIterator, r LockRange) LockIterator

Isolate ensures that the given segment's range is a subset of r by splitting at r.Start and r.End if necessary, and returns an updated iterator to the bounded segment. All existing iterators (including seg, but not including the returned iterators) are invalidated.

Isolate is usually used when mutating part of a single segment, or when mutating segments in a range where the first segment is not necessarily split, making use of SplitBefore/SplitAfter complex.

Preconditions: seg.Range().Overlaps(r).

func (*LockSet) LastGap 

func (s *LockSet) LastGap() LockGapIterator

LastGap returns the last gap in the set.

func (*LockSet) LastLargeEnoughGap 

func (s *LockSet) LastLargeEnoughGap(minSize uint64) LockGapIterator

LastLargeEnoughGap returns the last gap in the set with at least the given length. If no such gap exists, LastLargeEnoughGap returns a terminal iterator.

Precondition: trackGaps must be 1.

func (*LockSet) LastSegment 

func (s *LockSet) LastSegment() LockIterator

LastSegment returns the last segment in the set. If the set is empty, LastSegment returns a terminal iterator.

func (*LockSet) LowerBoundGap 

func (s *LockSet) LowerBoundGap(min uint64) LockGapIterator

LowerBoundGap returns the gap with the lowest range that is greater than or equal to min.

func (*LockSet) LowerBoundLargeEnoughGap 

func (s *LockSet) LowerBoundLargeEnoughGap(min, minSize uint64) LockGapIterator

LowerBoundLargeEnoughGap returns the first gap in the set with at least the given length and whose range contains a key greater than or equal to min. If no such gap exists, LowerBoundLargeEnoughGap returns a terminal iterator.

Precondition: trackGaps must be 1.

func (*LockSet) LowerBoundSegment 

func (s *LockSet) LowerBoundSegment(min uint64) LockIterator

LowerBoundSegment returns the segment with the lowest range that contains a key greater than or equal to min. If no such segment exists, LowerBoundSegment returns a terminal iterator.

func (*LockSet) LowerBoundSegmentSplitBefore 

func (s *LockSet) LowerBoundSegmentSplitBefore(min uint64) LockIterator

LowerBoundSegmentSplitBefore combines LowerBoundSegment and SplitBefore.

LowerBoundSegmentSplitBefore is usually used when mutating segments in a range while iterating them in order of increasing keys. In such cases, LowerBoundSegmentSplitBefore provides an iterator to the first segment to be mutated, suitable as the initial value for a loop variable.

func (*LockSet) Merge 

func (s *LockSet) Merge(first, second LockIterator) LockIterator

Merge attempts to merge two neighboring segments. If successful, Merge returns an iterator to the merged segment, and all existing iterators are invalidated. Otherwise, Merge returns a terminal iterator.

If first is not the predecessor of second, Merge panics.

func (*LockSet) MergeAll 

func (s *LockSet) MergeAll()

MergeAll merges all mergeable adjacent segments in the set. All existing iterators are invalidated.

func (*LockSet) MergeInsideRange 

func (s *LockSet) MergeInsideRange(r LockRange)

MergeInsideRange attempts to merge all adjacent segments that contain a key in the specific range. All existing iterators are invalidated.

MergeInsideRange only makes sense after mutating the set in a way that may change the mergeability of modified segments; callers should prefer to use MergePrev or MergeNext during the mutating loop instead (depending on the direction of iteration), in order to avoid a redundant search.

func (*LockSet) MergeNext 

func (s *LockSet) MergeNext(seg LockIterator) LockIterator

MergeNext attempts to merge the given segment with its successor if possible, and returns an updated iterator to the extended segment. All existing iterators (including seg, but not including the returned iterator) are invalidated.

MergeNext is usually used when mutating segments while iterating them in order of decreasing keys, to attempt merging of each mutated segment with its previously-mutated successor. In such cases, merging a mutated segment with its unmutated predecessor would incorrectly cause the latter to be skipped.

func (*LockSet) MergeOutsideRange 

func (s *LockSet) MergeOutsideRange(r LockRange)

MergeOutsideRange attempts to merge the segment containing r.Start with its predecessor, and the segment containing r.End-1 with its successor.

MergeOutsideRange only makes sense after mutating the set in a way that may change the mergeability of modified segments; callers should prefer to use MergePrev or MergeNext during the mutating loop instead (depending on the direction of iteration), in order to avoid two redundant searches.

func (*LockSet) MergePrev 

func (s *LockSet) MergePrev(seg LockIterator) LockIterator

MergePrev attempts to merge the given segment with its predecessor if possible, and returns an updated iterator to the extended segment. All existing iterators (including seg, but not including the returned iterator) are invalidated.

MergePrev is usually used when mutating segments while iterating them in order of increasing keys, to attempt merging of each mutated segment with its previously-mutated predecessor. In such cases, merging a mutated segment with its unmutated successor would incorrectly cause the latter to be skipped.

func (*LockSet) MergeUnchecked 

func (s *LockSet) MergeUnchecked(first, second LockIterator) LockIterator

MergeUnchecked attempts to merge two neighboring segments. If successful, MergeUnchecked returns an iterator to the merged segment, and all existing iterators are invalidated. Otherwise, MergeUnchecked returns a terminal iterator.

Precondition: first is the predecessor of second: first.NextSegment() == second, first == second.PrevSegment().

func (*LockSet) MutateFullRange 

func (s *LockSet) MutateFullRange(r LockRange, f func(seg LockIterator) bool)

MutateFullRange is equivalent to MutateRange, except that if any key in r that is visited before f returns false does not correspond to a segment, MutateFullRange panics.

func (*LockSet) MutateRange 

func (s *LockSet) MutateRange(r LockRange, f func(seg LockIterator) bool)

MutateRange applies the function f to all segments intersecting the range r, in order of ascending keys. Segments that lie partially outside r are split before f is called, such that f only observes segments entirely within r. Iterated segments are merged again after f is called. Non-empty gaps between segments are skipped. If a call to f returns false, MutateRange stops iteration immediately.

MutateRange invalidates all existing iterators.

N.B. f must not invalidate iterators into s.

func (*LockSet) Remove 

func (s *LockSet) Remove(seg LockIterator) LockGapIterator

Remove removes the given segment and returns an iterator to the vacated gap. All existing iterators (including seg, but not including the returned iterator) are invalidated.

func (*LockSet) RemoveAll 

func (s *LockSet) RemoveAll()

RemoveAll removes all segments from the set. All existing iterators are invalidated.

func (*LockSet) RemoveFullRange 

func (s *LockSet) RemoveFullRange(r LockRange) LockGapIterator

RemoveFullRange is equivalent to RemoveRange, except that if any key in the given range does not correspond to a segment, RemoveFullRange panics.

func (*LockSet) RemoveFullRangeWith 

func (s *LockSet) RemoveFullRangeWith(r LockRange, f func(seg LockIterator)) LockGapIterator

RemoveFullRangeWith is equivalent to RemoveRangeWith, except that if any key in the given range does not correspond to a segment, RemoveFullRangeWith panics.

func (*LockSet) RemoveRange 

func (s *LockSet) RemoveRange(r LockRange) LockGapIterator

RemoveRange removes all segments in the given range. An iterator to the newly formed gap is returned, and all existing iterators are invalidated.

RemoveRange searches the set to find segments to remove. If the caller already has an iterator to either end of the range of segments to remove, or if the caller needs to do additional work before removing each segment, iterate segments and call Remove in a loop instead.

func (*LockSet) RemoveRangeWith 

func (s *LockSet) RemoveRangeWith(r LockRange, f func(seg LockIterator)) LockGapIterator

RemoveRangeWith removes all segments in the given range. An iterator to the newly formed gap is returned, and all existing iterators are invalidated.

The function f is applied to each segment immediately before it is removed, in order of ascending keys. Segments that lie partially outside r are split before f is called, such that f only observes segments entirely within r. Non-empty gaps between segments are skipped.

RemoveRangeWith searches the set to find segments to remove. If the caller already has an iterator to either end of the range of segments to remove, or if the caller needs to do additional work before removing each segment, iterate segments and call Remove in a loop instead.

N.B. f must not invalidate iterators into s.

func (*LockSet) Span 

func (s *LockSet) Span() uint64

Span returns the total size of all segments in the set.

func (*LockSet) SpanRange 

func (s *LockSet) SpanRange(r LockRange) uint64

SpanRange returns the total size of the intersection of segments in the set with the given range.

func (*LockSet) Split 

func (s *LockSet) Split(seg LockIterator, split uint64) (LockIterator, LockIterator)

Split splits the given segment at the given key and returns iterators to the two resulting segments. All existing iterators (including seg, but not including the returned iterators) are invalidated.

If the segment cannot be split at split (because split is at the start or end of the segment's range, so splitting would produce a segment with zero length, or because split falls outside the segment's range altogether), Split panics.

func (*LockSet) SplitAfter 

func (s *LockSet) SplitAfter(seg LockIterator, end uint64) LockIterator

SplitAfter ensures that the given segment's end is at most end by splitting at end if necessary, and returns an updated iterator to the bounded segment. All existing iterators (including seg, but not including the returned iterator) are invalidated.

SplitAfter is usually used when mutating segments in a range. In such cases, when iterating segments in order of increasing keys, each iterated segment may extend beyond the end of the range to be mutated, and needs to be SplitAfter to ensure that only the part of the segment within the range is mutated. When iterating segments in order of decreasing keys, SplitBefore and SplitAfter exchange roles; i.e. SplitBefore needs to be invoked on each segment, while SplitAfter only needs to be invoked on the first.

Preconditions: seg.Start() < end.

func (*LockSet) SplitBefore 

func (s *LockSet) SplitBefore(seg LockIterator, start uint64) LockIterator

SplitBefore ensures that the given segment's start is at least start by splitting at start if necessary, and returns an updated iterator to the bounded segment. All existing iterators (including seg, but not including the returned iterator) are invalidated.

SplitBefore is usually when mutating segments in a range. In such cases, when iterating segments in order of increasing keys, the first segment may extend beyond the start of the range to be mutated, and needs to be SplitBefore to ensure that only the part of the segment within the range is mutated. When iterating segments in order of decreasing keys, SplitBefore and SplitAfter; i.e. SplitBefore needs to be invoked on each segment, while SplitAfter only needs to be invoked on the first.

Preconditions: start < seg.End().

func (*LockSet) SplitUnchecked 

func (s *LockSet) SplitUnchecked(seg LockIterator, split uint64) (LockIterator, LockIterator)

SplitUnchecked splits the given segment at the given key and returns iterators to the two resulting segments. All existing iterators (including seg, but not including the returned iterators) are invalidated.

Preconditions: seg.Start() < key < seg.End().

func (*LockSet) StateFields 

func (s *LockSet) StateFields() []string

func (*LockSet) StateLoad 

func (s *LockSet) StateLoad(ctx context.Context, stateSourceObject state.Source)

+checklocksignore

func (*LockSet) StateSave 

func (s *LockSet) StateSave(stateSinkObject state.Sink)

+checklocksignore

func (*LockSet) StateTypeName 

func (s *LockSet) StateTypeName() string

func (*LockSet) String 

func (s *LockSet) String() string

String stringifies a Set for debugging.

func (*LockSet) TryInsertRange 

func (s *LockSet) TryInsertRange(r LockRange, val Lock) LockIterator

TryInsertRange attempts to insert the given segment into the set. If the new segment can be merged with adjacent segments, TryInsertRange will do so. TryInsertRange returns an iterator to the segment containing the inserted value (which may have been merged with other values). All existing iterators (excluding the returned iterator) are invalidated.

If the new segment would overlap an existing segment, TryInsertRange does nothing and returns a terminal iterator.

TryInsertRange searches the set to find the gap to insert into. If the caller already has the appropriate GapIterator, or if the caller needs to do additional work between finding the gap and insertion, use Insert instead.

func (*LockSet) TryInsertWithoutMergingRange 

func (s *LockSet) TryInsertWithoutMergingRange(r LockRange, val Lock) LockIterator

TryInsertWithoutMergingRange attempts to insert the given segment into the set. If successful, it returns an iterator to the inserted segment; all existing iterators (excluding the returned iterator) are invalidated. If the new segment would overlap an existing segment, TryInsertWithoutMergingRange does nothing and returns a terminal iterator.

TryInsertWithoutMergingRange searches the set to find the gap to insert into. If the caller already has the appropriate GapIterator, or if the caller needs to do additional work between finding the gap and insertion, use InsertWithoutMerging instead.

func (*LockSet) Unisolate 

func (s *LockSet) Unisolate(seg LockIterator) LockIterator

Unisolate attempts to merge the given segment with its predecessor and successor if possible, and returns an updated iterator to the extended segment. All existing iterators (including seg, but not including the returned iterator) are invalidated.

Unisolate is usually used in conjunction with Isolate when mutating part of a single segment in a way that may affect its mergeability. For the reasons described by MergePrev and MergeNext, it is usually incorrect to use the return value of Unisolate in a loop variable.

func (*LockSet) UpperBoundGap 

func (s *LockSet) UpperBoundGap(max uint64) LockGapIterator

UpperBoundGap returns the gap with the highest range that is less than or equal to max.

func (*LockSet) UpperBoundLargeEnoughGap 

func (s *LockSet) UpperBoundLargeEnoughGap(max, minSize uint64) LockGapIterator

UpperBoundLargeEnoughGap returns the last gap in the set with at least the given length and whose range contains a key less than or equal to max. If no such gap exists, UpperBoundLargeEnoughGap returns a terminal iterator.

Precondition: trackGaps must be 1.

func (*LockSet) UpperBoundSegment 

func (s *LockSet) UpperBoundSegment(max uint64) LockIterator

UpperBoundSegment returns the segment with the highest range that contains a key less than or equal to max. If no such segment exists, UpperBoundSegment returns a terminal iterator.

func (*LockSet) UpperBoundSegmentSplitAfter 

func (s *LockSet) UpperBoundSegmentSplitAfter(max uint64) LockIterator

UpperBoundSegmentSplitAfter combines UpperBoundSegment and SplitAfter.

UpperBoundSegmentSplitAfter is usually used when mutating segments in a range while iterating them in order of decreasing keys. In such cases, UpperBoundSegmentSplitAfter provides an iterator to the first segment to be mutated, suitable as the initial value for a loop variable.

func (*LockSet) VisitFullRange 

func (s *LockSet) VisitFullRange(r LockRange, f func(seg LockIterator) bool)

VisitFullRange is equivalent to VisitRange, except that if any key in r that is visited before f returns false does not correspond to a segment, VisitFullRange panics.

func (*LockSet) VisitRange 

func (s *LockSet) VisitRange(r LockRange, f func(seg LockIterator) bool)

VisitRange applies the function f to all segments intersecting the range r, in order of ascending keys. Segments will not be split, so f may be called on segments lying partially outside r. Non-empty gaps between segments are skipped. If a call to f returns false, VisitRange stops iteration immediately.

N.B. f must not invalidate iterators into s.

type LockType 

type LockType int

LockType is a type of regional file lock. 

const (
	// ReadLock describes a POSIX regional file lock to be taken
	// read only.  There may be multiple of these locks on a single
	// file region as long as there is no writer lock on the same
	// region.
	ReadLock LockType = iota

	// WriteLock describes a POSIX regional file lock to be taken
	// write only.  There may be only a single holder of this lock
	// and no read locks.
	WriteLock
)

type LockdynamicGap 

type LockdynamicGap [LocktrackGaps]uint64

dynamicGap is a type that disappears if trackGaps is 0.

func (*LockdynamicGap) Get 

func (d *LockdynamicGap) Get() uint64

Get returns the value of the gap.

Precondition: trackGaps must be non-zero.

func (*LockdynamicGap) Set 

func (d *LockdynamicGap) Set(v uint64)

Set sets the value of the gap.

Precondition: trackGaps must be non-zero.

type Locknode 

type Locknode struct {
	// contains filtered or unexported fields
}

+stateify savable

func (*Locknode) StateFields 

func (n *Locknode) StateFields() []string

func (*Locknode) StateLoad 

func (n *Locknode) StateLoad(ctx context.Context, stateSourceObject state.Source)

+checklocksignore

func (*Locknode) StateSave 

func (n *Locknode) StateSave(stateSinkObject state.Sink)

+checklocksignore

func (*Locknode) StateTypeName 

func (n *Locknode) StateTypeName() string

func (*Locknode) String 

func (n *Locknode) String() string

String stringifies a node (and all of its children) for debugging.

type Locks 

type Locks struct {
	// contains filtered or unexported fields
}

Locks is a thread-safe wrapper around a LockSet.

+stateify savable

func (*Locks) EventRegister 

func (l *Locks) EventRegister(e *waiter.Entry) error

EventRegister implements waiter.Waitable.EventRegister.

func (*Locks) EventUnregister 

func (l *Locks) EventUnregister(e *waiter.Entry)

EventUnregister implements waiter.Waitable.EventUnregister.

func (*Locks) LockRegion 

func (l *Locks) LockRegion(ctx context.Context, uid UniqueID, ownerPID int32, t LockType, r LockRange, ofd bool, block bool) error

LockRegion attempts to acquire a typed lock for the uid on a region of a file. Returns nil if successful in locking the region, otherwise an appropriate error is returned.

func (*Locks) Readiness 

func (l *Locks) Readiness(waiter.EventMask) waiter.EventMask

Readiness always returns zero.

func (*Locks) StateFields 

func (l *Locks) StateFields() []string

func (*Locks) StateLoad 

func (l *Locks) StateLoad(ctx context.Context, stateSourceObject state.Source)

+checklocksignore

func (*Locks) StateSave 

func (l *Locks) StateSave(stateSinkObject state.Sink)

+checklocksignore

func (*Locks) StateTypeName 

func (l *Locks) StateTypeName() string

func (*Locks) TestRegion 

func (l *Locks) TestRegion(ctx context.Context, uid UniqueID, t LockType, r LockRange, ofd bool) linux.Flock

TestRegion checks whether the lock holder identified by uid can hold a lock of type t on range r. It returns a Flock struct representing this information as the F_GETLK fcntl does.

Note that the PID returned in the flock structure is relative to the root PID namespace. It needs to be converted to the caller's PID namespace before returning to userspace.

func (*Locks) UnlockRegion 

func (l *Locks) UnlockRegion(uid UniqueID, r LockRange)

UnlockRegion attempts to release a lock for the uid on a region of a file. This operation is always successful, even if there did not exist a lock on the requested region held by uid in the first place.

type OwnerInfo 

type OwnerInfo struct {
	// PID is the process ID of the lock owner.
	PID int32
	// OFD is whether this is an open file descriptor lock.
	OFD bool
}

OwnerInfo describes the owner of a lock.

+stateify savable

func (*OwnerInfo) StateFields 

func (o *OwnerInfo) StateFields() []string

func (*OwnerInfo) StateLoad 

func (o *OwnerInfo) StateLoad(ctx context.Context, stateSourceObject state.Source)

+checklocksignore

func (*OwnerInfo) StateSave 

func (o *OwnerInfo) StateSave(stateSinkObject state.Sink)

+checklocksignore

func (*OwnerInfo) StateTypeName 

func (o *OwnerInfo) StateTypeName() string

type UniqueID 

type UniqueID any

UniqueID is a unique identifier of the holder of a regional file lock.

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