Status: Accepted Owner: stephane.ducasse Labels: Milestone-1.3 Type-Squeak New issue 3340 by stephane.ducasse: ThreadSafe DebuggerMethodMap http://code.google.com/p/pharo/issues/detail?id=3340 We should have a look at that fix from squeak A new version of Tools was added to project The Inbox: http://source.squeak.org/inbox/Tools-ul.278.mcz ==================== Summary ==================== Name: Tools-ul.278 Author: ul Time: 15 November 2010, 8:46:10.672 am UUID: d03d7286-1db1-f943-9e1c-6e86626b5f89 Ancestors: Tools-ul.277 Thread-safe DebuggerMethodMap =============== Diff against Tools-ul.277 =============== Item was changed: Object subclass: #DebuggerMethodMap instanceVariableNames: 'timestamp methodReference methodNode abstractSourceRanges sortedSourceMap' + classVariableNames: 'AccessLock MapCache MapCacheEntries' - classVariableNames: 'MapCache MapCacheEntries' poolDictionaries: '' category: 'Tools-Debugger'! !DebuggerMethodMap commentStamp: '<historical>' prior: 0! I am a place-holder for information needed by the Debugger to inspect method activations. I insulate the debugger from details of code generation such as exact bytecode offsets and temporary variable locations. I have two concreate subclasses, one for methods compiled using BlueBook blocks and one for methods compiled using Closures. These classes deal with temporary variable access. My function is to abstract the source map away from actual bytecode pcs to abstract bytecode pcs. To reduce compilation time I try and defer as much computation to access time as possible as instances of me will be created after each compilation. I maintain a WeakIdentityDictionary of method to DebuggerMethodMap to cache maps. I refer to my method through a WeakArray to keep the map cache functional. If the reference from a DebuggerMethodMap to its method were strong then the method would never be dropped from the cache because the reference from its map would keep it alive.! Item was changed: ----- Method: DebuggerMethodMap class>>cacheDebugMap:forMethod: (in category 'debugger support') ----- cacheDebugMap: aDebuggerMethodMap forMethod: aCompiledMethod + + ^self protected: [ + MapCache size >= MapCacheEntries ifTrue: [ + MapCache slowSize >= MapCacheEntries + ifFalse: [ MapCache rehash ] + ifTrue: [ + | mapsByAge | + mapsByAge := MapCache keys sort: [ :m1 :m2 | + "We are holding strongly on the keys, so #at: is suitable." + (MapCache at: m1) timestamp < (MapCache at: m2) timestamp]. + mapsByAge from: 1 to: mapsByAge size - MapCacheEntries do: [ :each | + MapCache removeKey: each ] ] ]. + MapCache + at: aCompiledMethod + put: aDebuggerMethodMap ]! - MapCache finalizeValues. - [MapCache size >= MapCacheEntries] whileTrue: - [| mapsByAge | - mapsByAge := MapCache keys asArray sort: - [:m1 :m2| - (MapCache at: m1) timestamp - < (MapCache at: m2) timestamp]. - mapsByAge notEmpty ifTrue: "There be race conditions and reentrancy issues here" - [MapCache removeKey: mapsByAge last]]. - - ^MapCache - at: aCompiledMethod - put: aDebuggerMethodMap! Item was changed: ----- Method: DebuggerMethodMap class>>forMethod: (in category 'instance creation') ----- forMethod: aMethod "<CompiledMethod>" "Answer a DebuggerMethodMap suitable for debugging activations of aMethod. Answer an existing instance from the cache if it exists, cacheing a new one if required." + + ^self protected: [ + MapCache + at: aMethod + ifAbsent: [self + cacheDebugMap: + (self + forMethod: aMethod + methodNode: aMethod methodNode) + forMethod: aMethod] ]! - ^MapCache - at: aMethod - ifAbsent: [self - cacheDebugMap: - (self - forMethod: aMethod - methodNode: aMethod methodNode) - forMethod: aMethod]! Item was added: + ----- Method: DebuggerMethodMap class>>protected: (in category 'synchronization') ----- + protected: aBlock + + ^(AccessLock ifNil: [ AccessLock := Mutex new ]) critical: aBlock! Item was changed: ----- Method: DebuggerMethodMap class>>voidMapCache (in category 'class initialization') ----- voidMapCache + + self protected: [ + MapCache := WeakIdentityKeyDictionary new. + MapCacheEntries := 16 ]! - MapCache := WeakIdentityKeyDictionary new. - MapCacheEntries := 16!