Florian Klaempfl wrote: > Micha Nelissen schrieb: >> Florian Klaempfl wrote: >>> procedure p;synchronized mycriticialsection; >>> >>> Any suggestions about doing it better? >> >> How to avoid deadlocks? > > Indeed, I'am open to any suggestions :) Just an idea: maybe a global > call tree analysis with a call tree attributed with critical section > information can find potential deadlocks?
Just some additional testing info and things to think about. *) Performance of non granular locks is poor. *) Creating 50K+ of lock instances makes the OS behave strange, so to fine granualer does not help either :-) Simplest working Deadlock Avoidance strategys is: Lock all resources at the same time in the same order. Thread x LOCK A LOCK B LOCK C ... Work .... UNLOCK C UNLOCK B UNLOCK A Thread x LOCK B LOCK C ... Work ... UNLOCK C UNLOCK B This way deadlocks are impossible. As this is sometimes not possible - we use deadlock detection in our software. (as classical database servers are doing it :-)) I describe it brief: Everytime we lock in a thread we post a event to an non-blocking queue (Michael&Scott), similar on unlocking. The MS Queue is fast and does not block. At the other side we Detect the deadlocks by time (like a asynchrounous logger). All our Locked operations are designed to take a small amount of time (say some milliseconds). When we detect a nonpairing timedifference of say one second, we found the deadlock and have to correct the code. This is a debugging tool, wich does not save design time. But saves huge amount of time searching for deadlocks. IMHO a full graph-theoretic cyclic redundancy check would be to much waste of time - inefficient. Another aproach would be STM. (software transactional memory). For theory about locks: Hector Garcia Molina, j.Ullman, J. Widom / DATABASE Systems the complete Book. Or hardcore: http://www.cs.rochester.edu/~scott/ Greets, helmut _______________________________________________ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
