[freenet-dev] [freenet-cvs] r18975 - trunk/freenet/src/freenet/client/async

[Matthew Toseland]

On Saturday 05 April 2008 03:50, Florent Daignière wrote:
> * Matthew Toseland <toad at amphibian.dyndns.org> [2008-04-04 19:22:27]:
> 
> > On Friday 04 April 2008 07:05, nextgens at freenetproject.org wrote:
> > > Author: nextgens
> > > Date: 2008-04-04 06:05:54 +0000 (Fri, 04 Apr 2008)
> > > New Revision: 18975
> > > 
> > > Modified:
> > >    trunk/freenet/src/freenet/client/async/SplitFileInserterSegment.java
> > > Log:
> > > Simplify a few things synchronization-wise declaring a few variables 
> > volatile 
> > 
> > I thought there were issues with volatile? Like it's not deterministic, 
and 
> > you really should use locking in all nontrivial cases?
> 
> I suggest you read
> http://www.javaperformancetuning.com/tips/volatile.shtml :)

"Note however that volatile has been incompletely implemented in most JVMs. 
Using volatile may not help to achieve the results you desire (yes this is a 
JVM bug, but its been low priority until recently)."

Presumably this doesn't include the mainline Sun VM.

"NOTE THE TIP "volatile primitive datatypes have atomic ++ operations" HAS 
BEEN SHOWN TO BE INVALID"

So never use volatile integers/longs/shorts.

Hmmm.
> 
> Two things to add: 
> 	1) there is no significant performance cost for
> reading a volatile on x86
> 	2) The SplitFileInserterSegment class is already a synchronization
> nightmare so we'd better reduce the locking to the minimum there : we still
> had some unsynchronized accesses to those booleans.
> 
> I think that making those booleans volatile is a step forward fighting
> the "requests don't finish" kind of bugs which are likely to be
> caused by race-conditions.
> 
Have you seen complaints of splitfile *inserts* not finishing? AFAIK reports 
are generally of requests not finishing...
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: not available
Url : http://emu.freenetproject.org/pipermail/devl/attachments/20080405/9832d64b/attachment.pgp