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https://issues.apache.org/jira/browse/FELIX-5621?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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David Jencks updated FELIX-5621:
--------------------------------
Description:
Thanks to Brent Daniels for pointing this out.
Setting service properties from returning properties from event methods is not
thread safe and does not appear to be possible to make thread safe, as
synchronizing will almost certainly produce deadlocks.
I think use of ExtComponentContext could be thread safe using code similar
to....
final AtomicReference<Dictionary<String, Object>> propRef;
...
Dictionary<String, Object> oldProps;
Dictionary<String, Object> newProps;
do {
synchronized(propRef) {
oldProps = propRef.get();
newProps = new Hashtable<>(oldProps);
}
//update newProps with new information
extComponentContext.setServiceProperties(newProps);
} while ( propsRef.compareAndSet( oldProps, newProps)}
was:
Thanks to Brent Daniels for pointing this out.
Setting service properties from event methods is not thread safe and does not
appear to be possible to make thread safe, as synchronizing will almost
certainly produce deadlocks. This applies to both setting the properties on
ExtComponentContext or returning a properties map.
If ExtComponentContext reliably provided a change counter and a compareAndSet
method then it could be used in e.g.
{code}
int cc;
Dictionary<String, Object> newProps;
do {
cc = etc.getChangeCount();
newProps = new Hashtable<>(ecc.getProperties());
//update properties
} while (!ecc.compareAndSet(cc, newProps)}
{code}
I don't think this can be implemented unless ServiceRegistration provides the
same API. Certainly the felix ServiceRegistration implementation is not thread
safe.
> [DS] event methods setting service properties not thread safe
> -------------------------------------------------------------
>
> Key: FELIX-5621
> URL: https://issues.apache.org/jira/browse/FELIX-5621
> Project: Felix
> Issue Type: Bug
> Components: Declarative Services (SCR)
> Affects Versions: scr-2.0.8
> Reporter: David Jencks
>
> Thanks to Brent Daniels for pointing this out.
> Setting service properties from returning properties from event methods is
> not thread safe and does not appear to be possible to make thread safe, as
> synchronizing will almost certainly produce deadlocks.
> I think use of ExtComponentContext could be thread safe using code similar
> to....
> final AtomicReference<Dictionary<String, Object>> propRef;
> ...
> Dictionary<String, Object> oldProps;
> Dictionary<String, Object> newProps;
> do {
> synchronized(propRef) {
> oldProps = propRef.get();
> newProps = new Hashtable<>(oldProps);
> }
> //update newProps with new information
> extComponentContext.setServiceProperties(newProps);
> } while ( propsRef.compareAndSet( oldProps, newProps)}
>
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