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http://issues.apache.org/bugzilla/show_bug.cgi?id=40167 Summary: Race condition in SoftReferenceCache.java wedges updater thread Product: Batik Version: 1.6 Platform: All OS/Version: Linux Status: NEW Severity: critical Priority: P2 Component: Utilities AssignedTo: [email protected] ReportedBy: [EMAIL PROTECTED] There is race condition bug in SoftReferenceCache.java that has the net effect of wrongly putting an entry in the cache with null value. This causes all subsequent requests for that value to hang forever in Object.wait() (inside requestImpl()). The bug stems from the code's failure to discern between the two meanings of HashMap.get(key) returning null, i.e., (a) the key does not exist in the map, or (b) the key exists but has a null value. Sequence of events that trigger this bug: 1. putImpl(key, ref): key -> ref added to map (ref is a SoftRefKey) 2. soft reference to value 'ref' is cleared by JVM 3. clearImpl(key): key is cleared from the map 4. JVM reference queue thread invokes ref.cleared() 5. ref.cleared() does cache.map.remove(key), which returns null 6. null != this, so cleared() then does cache.map.put(key, null) 7. victim thread invokes requestImpl(key), sees that the map contains the key but with null value, and so waits forever Patch to fix this bug: --- sources/org/apache/batik/util/SoftReferenceCache.java.orig 2006-08-01 20:35:11.000000000 -0500 +++ sources/org/apache/batik/util/SoftReferenceCache.java 2006-08-02 08:57:12.301341434 -0500 @@ -173,6 +173,8 @@ SoftReferenceCache cache = SoftReferenceCache.this; if (cache == null) return; // Can't really happen. synchronized (cache) { + if (!cache.map.containsKey(key)) + return; Object o = cache.map.remove(key); if (this == o) { // Notify other threads that they may have -- Configure bugmail: http://issues.apache.org/bugzilla/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are the assignee for the bug, or are watching the assignee. --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
