Some more thoughts about this...
The wait() call in the getService() method is as follows:
synchronized (this)
{
// First make sure that no existing operation is currently
// being performed by another thread on the service registration.
for (Object o = m_lockedRegsMap.get(reg); (o != null); o =
m_lockedRegsMap.get(reg))
{
// We don't allow cycles when we call out to the
service factory.
if (o.equals(Thread.currentThread()))
{
throw new ServiceException(
"ServiceFactory.getService() resulted in a cycle.",
ServiceException.FACTORY_ERROR,
null);
}
// Otherwise, wait for it to be freed.
try
{
wait();
}
catch (InterruptedException ex)
{
Thread.currentThread().interrupt();
}
}
I'm wondering why the code doesn't break out of the loop in the catch block?
Cheers,
David
On 20 March 2015 at 12:16, David Bosschaert <[email protected]> wrote:
> Hi all,
>
> I'm looking at an issue that I'm experiencing (with Felix 4.6.1/Java
> 7) where the ServiceRegsitry.getService() [1] method seems to be in an
> endless loop. It doesn't happen very often, but when it does happen
> the thread executing getService() seems to never exit that method
> apparently switch between the following two states:
>
> 1: Thread 22059: (state = IN_VM)
> - java.lang.Object.wait(long) @bci=0 (Compiled frame; information may
> be imprecise)
> - java.lang.Object.wait() @bci=2, line=503 (Compiled frame)
> -
> org.apache.felix.framework.ServiceRegistry.getService(org.osgi.framework.Bundle,
> org.osgi.framework.ServiceReference, boolean) @bci=86, line=313
> (Compiled frame)
>
> 2: Thread 22059: (state = IN_VM)
> - java.lang.Throwable.fillInStackTrace(int) @bci=0 (Compiled frame;
> information may be imprecise)
> - java.lang.Throwable.fillInStackTrace() @bci=16, line=783 (Compiled frame)
> - java.lang.Throwable.<init>() @bci=24, line=250 (Compiled frame)
> - java.lang.Exception.<init>() @bci=1, line=54 (Compiled frame)
> - java.lang.InterruptedException.<init>() @bci=1, line=57 (Compiled frame)
> - java.lang.Object.wait(long) @bci=0 (Compiled frame)
> - java.lang.Object.wait() @bci=2, line=503 (Compiled frame)
> -
> org.apache.felix.framework.ServiceRegistry.getService(org.osgi.framework.Bundle,
> org.osgi.framework.ServiceReference, boolean) @bci=86, line=313
> (Compiled frame)
>
> Even though the thread is executing wait() all of the other Felix
> SR-accessing threads are blocked on the Service Registry lock. The net
> effect is that any operation on the Service Registry is blocked.
> There is one thing that I don't understand and that is that in the
> above frames the lock should really be released, as the code is in
> wait(). However, it seems like the lock is still held because none of
> the other threads are getting access to the Service Registry. For
> example another such thread is the following which is actually about
> to decrease the usage count on the service and then call notifyAll():
>
> Thread 48643: (state = BLOCKED)
> -
> org.apache.felix.framework.ServiceRegistry.getService(org.osgi.framework.Bundle,
> org.osgi.framework.ServiceReference, boolean) @bci=241, line=367
> (Compiled frame)
> -
> org.apache.felix.framework.util.EventDispatcher.filterListenersUsingHooks(org.osgi.framework.ServiceEvent,
> org.osgi.framework.launch.Framework, java.util.Map) @bci=349, line=618
> (Compiled frame)
> -
> org.apache.felix.framework.util.EventDispatcher.fireServiceEvent(org.osgi.framework.ServiceEvent,
> java.util.Dictionary, org.osgi.framework.launch.Framework) @bci=33,
> line=542 (Interpreted frame)
> -
> org.apache.felix.framework.Felix.fireServiceEvent(org.osgi.framework.ServiceEvent,
> java.util.Dictionary) @bci=7, line=4547 (Compiled frame)
> -
> org.apache.felix.framework.Felix.access$000(org.apache.felix.framework.Felix,
> org.osgi.framework.ServiceEvent, java.util.Dictionary) @bci=3,
> line=106 (Compiled frame)
> -
> org.apache.felix.framework.Felix$1.serviceChanged(org.osgi.framework.ServiceEvent,
> java.util.Dictionary) @bci=6, line=436 (Compiled frame)
> -
> org.apache.felix.framework.ServiceRegistry.unregisterService(org.osgi.framework.Bundle,
> org.osgi.framework.ServiceRegistration) @bci=100, line=165 (Compiled
> frame)
> - org.apache.felix.framework.ServiceRegistrationImpl.unregister()
> @bci=52, line=140 (Interpreted frame)
>
> I just don't understand why all the other threads are blocked on the
> service registry. I'm probably missing something simple, so would be
> grateful if someone else has an idea.
>
> Many thanks,
>
> David
>
> [1]
> http://svn.apache.org/repos/asf/felix/releases/org.apache.felix.framework-4.6.1/src/main/java/org/apache/felix/framework/ServiceRegistry.java
