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From "Richard S. Hall (JIRA)" <j...@apache.org>
Subject [jira] Commented: (FELIX-2400) High contention (or deadlock) in PackageAdmin and StartLevel
Date Wed, 09 Jun 2010 14:35:12 GMT

    [ https://issues.apache.org/jira/browse/FELIX-2400?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12877087#action_12877087
] 

Richard S. Hall commented on FELIX-2400:
----------------------------------------

It is not clear to me why there would be interference between pa.refreshPackages() and pa.resolveBundles(),
since both need to acquire the global lock and therefore by definition they will be serialized.
Of course, there is a race condition regarding which will happen first in your scenario.

Regardinging, the interference with start level, there could be something there and that is
tricky. We'd have to investigate it more. This area hasn't change much for framework 3.0 so
i'd expect the issue to be the same, but feel free to test it.

> High contention (or deadlock) in PackageAdmin and StartLevel 
> -------------------------------------------------------------
>
>                 Key: FELIX-2400
>                 URL: https://issues.apache.org/jira/browse/FELIX-2400
>             Project: Felix
>          Issue Type: Bug
>          Components: Framework
>    Affects Versions: framework-2.0.5
>         Environment: Felix 2.0.5
> java version "1.6.0_12"
> Java(TM) SE Runtime Environment (build 1.6.0_12-b04)
> Java HotSpot(TM) 64-Bit Server VM (build 11.2-b01, mixed mode)
> SunOS castor 5.10 Generic_138888-06 sun4u sparc SUNW,Sun-Fire-V890
>            Reporter: Alexander Berger
>
> Imagine the following code:
> void createProblem(PackageAdmin pa, StartLevel sl, Bundle bundles[], int level){
>    for ( final Bundle b : bundles) {
>       sl.setBundleStartLevel(b, level);
>    }
>    pa.refreshPackages(null);
>    pa.resolveBundles(null);
> }
> If there have been many bundles updated or uninstalled the code above might create what
looks like a deadlock (see Stack traces below)
> but in fact is a high contention problem. On our system (16 core Sun Sparcv9, 64GB) with
about 20 bundles (all updated, so refresh will be busy) 
> this will result in very poor runtime performance, it will take about 30 to 60 minutes
for pa.resolveBundles(null) to return.
> The problem lies in the asynchronous nature of setBundleStartLevel/refreshPackages and
the way that Felix uses locking (acquireGlobalLock and acquireBundleLock). For example the
following code works fine (and for pa.resolveBundles(null) returns within some seconds) but
poses the problem of how to implement "magicWait":
> void createNoProblem(PackageAdmin pa, StartLevel sl, Bundle bundles[], int level){
>    for ( final Bundle b : bundles) {
>       sl.setBundleStartLevel(b, level);
>    }
>    // wait until the asynchronous sl.setBundleStartLevel logic has finished
>    magicWait(sl);
>    pa.refreshPackages(null);
>    // wait until the asynchronous pa.refreshPackages logic has finished
>    magicWait(pa); 
>    pa.resolveBundles(null);
> }
> At the moment I solved the problem by patching PackageAdminImpl like this (I know this
is an ugly solution buts its only a show case):
> public boolean isDone() {
>    synchronized(this) {
>       final Bundle tmp[][] = m_reqBundles;
>       return tmp == null || tmp.length == 0;
>    }
> }
> And implementing magicWait like this:
> void magicWait(final PackageAdmin pa){
>     final Method method = pa.getClass().getMethod("isDone");
>     method.setAccessible(true);
>     while ( ! (Boolean)method.invoke(pa) ) {
>        Thread.yield();
>     }
> }
> Then I did something similar for StartLevel. 
> For me this patch/work around is fine for the moment but I think the problem 
> should be investigated and solved in the Felix framework.
> "FelixPackageAdmin" daemon prio=3 tid=0x00000001005ac800 nid=0x1a in Object.wait() [0xffffffff4f6fe000]
>    java.lang.Thread.State: WAITING (on object monitor)
> 	at java.lang.Object.wait(Native Method)
> 	- waiting on <0xffffffff554000e0> (a [Ljava.lang.Object;)
> 	at java.lang.Object.wait(Object.java:485)
> 	at org.apache.felix.framework.Felix.acquireGlobalLock(Felix.java:4535)
> 	- locked <0xffffffff554000e0> (a [Ljava.lang.Object;)
> 	at org.apache.felix.framework.Felix.refreshPackages(Felix.java:3314)
> 	at org.apache.felix.framework.PackageAdminImpl.run(PackageAdminImpl.java:331)
> 	at java.lang.Thread.run(Unknown Source)
>    Locked ownable synchronizers:
> 	- None
> 	
> "FelixStartLevel" daemon prio=3 tid=0x0000000100848000 nid=0x19 in Object.wait() [0xffffffff4f8fe000]
>    java.lang.Thread.State: WAITING (on object monitor)
> 	at java.lang.Object.wait(Native Method)
> 	- waiting on <0xffffffff554000e0> (a [Ljava.lang.Object;)
> 	at java.lang.Object.wait(Object.java:485)
> 	at org.apache.felix.framework.Felix.acquireBundleLock(Felix.java:4462)
> 	- locked <0xffffffff554000e0> (a [Ljava.lang.Object;)
> 	at org.apache.felix.framework.Felix.setBundleStartLevel(Felix.java:1266)
> 	at org.apache.felix.framework.StartLevelImpl.run(StartLevelImpl.java:270)
> 	at java.lang.Thread.run(Unknown Source)
>    Locked ownable synchronizers:
> 	- None
> 	
> "OSKi" prio=3 tid=0x00000001006ea800 nid=0x1b runnable [0xffffffff4f4fd000]
>    java.lang.Thread.State: RUNNABLE
> 	at org.apache.felix.framework.searchpolicy.ResolvedPackage.clone(ResolvedPackage.java:62)
> 	at org.apache.felix.framework.searchpolicy.Resolver.isClassSpaceConsistent(Resolver.java:846)
> 	at org.apache.felix.framework.searchpolicy.Resolver.isClassSpaceConsistent(Resolver.java:807)
> 	at org.apache.felix.framework.searchpolicy.Resolver.isClassSpaceConsistent(Resolver.java:807)
> 	at org.apache.felix.framework.searchpolicy.Resolver.findConsistentClassSpace(Resolver.java:549)
> 	at org.apache.felix.framework.searchpolicy.Resolver.resolve(Resolver.java:103)
> 	at org.apache.felix.framework.Felix$FelixResolver.resolve(Felix.java:3861)
> 	at org.apache.felix.framework.Felix.resolveBundle(Felix.java:3292)
> 	at org.apache.felix.framework.Felix.resolveBundles(Felix.java:3267)
> 	at org.apache.felix.framework.PackageAdminImpl.resolveBundles(PackageAdminImpl.java:288)
>             at Test.createProblem(Test.java:10)

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