Bug 811370

Shortened stacktrace:
org.eclipse.core.runtime.CoreException: Plug-in org.eclipse.mylyn.tasks.ui was unable to load class org.eclipse.mylyn.internal.tasks.ui.PlanningPerspectiveFactory.
Caused by: org.eclipse.core.runtime.internal.adaptor.EclipseLazyStarter$TerminatingClassNotFoundException: An error occurred while automatically activating bundle org.eclipse.mylyn.tasks.ui (363).
Caused by: org.osgi.framework.BundleException: The activator org.eclipse.mylyn.internal.tasks.ui.TasksUiPlugin for bundle org.eclipse.mylyn.tasks.ui is invalid
Caused by: java.lang.NoClassDefFoundError: org/eclipse/mylyn/monitor/ui/IUserAttentionListener
Caused by: org.eclipse.core.runtime.internal.adaptor.EclipseLazyStarter$TerminatingClassNotFoundException: An error occurred while automatically activating bundle org.eclipse.mylyn.monitor.ui (356).
Caused by: org.osgi.framework.BundleException: Exception in org.eclipse.mylyn.internal.monitor.ui.MonitorUiPlugin.start() of bundle org.eclipse.mylyn.monitor.ui.
Caused by: java.lang.LinkageError: loader constraint violation in interface itable initialization: when resolving method "org.eclipse.core.internal.plugins.PluginDescriptor.getPlugin()Lorg/eclipse/core/runtime/Plugin;" the class loader (instance of org/eclipse/osgi/internal/baseadaptor/DefaultClassLoader) of the current class, org/eclipse/core/internal/plugins/PluginDescriptor, and the class loader (instance of org/eclipse/osgi/internal/baseadaptor/DefaultClassLoader) for interface org/eclipse/core/runtime/IPluginDescriptor have different Class objects for the type or.getPlugin()Lorg/eclipse/core/runtime/Plugin; used in the signature

The same stacktrace cut short:
java.lang.LinkageError (differences between what version of PluginDescriptor.getPlugin  org.eclipse.monitor.ui requires to run and what is actually loaded) cause the perspective to be unavailable at runtime (it is declared, but cannot be switched on). 

I am investigating the cause.

Andrew, 
could you look for duplicated plugins in your installation? Specifically for org.eclipse.core.runtime*. I can't imagine a situation where singletons cause such a situation.

I used uniq -D and see no dupes in /usr/{share,lib64}/eclipse nor in my ~/.eclipse/.../bundles.info or ~/.eclipse.

plugins may have different qualifiers.

(In reply to comment #5)
> plugins may have different qualifiers.

Oops :)  I ran the following and got nothing interesting as output:

find /usr/{share,lib,lib64}/eclipse ~/.eclipse -exec "basename" "{}" ";"| sed "s/_.*//" | uniq -D

cat ~/.eclipse/org.eclipse.platform_4.2.0_793567567/configuration/org.eclipse.equinox.simpleconfigurator/bundles.info|sed "s/_.*//" | uniq -D

eclipse-rcp:  /usr/lib64/eclipse/plugins/org.eclipse.core.runtime_3.8.0.v20120308-2101.jar
eclipse-platform:  /usr/lib64/eclipse/plugins/org.eclipse.core.runtime.compatibility_3.2.200.v20120308-2101.jar

After upgrading a bunch of dependencies to their rawhide versions, things work!  These are the packages that I upgraded:

  Updating   : tomcat-servlet-3.0-api-7.0.27-2.fc18.noarch                 1/25 
  Updating   : tomcat-jsp-2.2-api-7.0.27-2.fc18.noarch                     2/25 
  Updating   : sac-1.3-12.fc17.noarch                                      3/25 
  Updating   : xml-commons-apis-1.4.01-6.fc17.noarch                       4/25 
  Updating   : tomcat-el-2.2-api-7.0.27-2.fc18.noarch                      5/25 
  Updating   : lucene-2.9.4-8.fc17.noarch                                  6/25 
  Installing : jai-imageio-core-1.2-0.7.20100217cvs.fc17.x86_64            7/25 
  Updating   : batik-1.8-0.1.svn1230816.fc18.noarch                        8/25 
  Updating   : batik-squiggle-1.8-0.1.svn1230816.fc18.noarch               9/25 
  Updating   : lucene-contrib-2.9.4-8.fc17.noarch                         10/25 
  Updating   : tomcat-lib-7.0.27-2.fc18.noarch                            11/25 
  Updating   : apache-commons-el-1.0-23.fc17.noarch                       12/25 
  Updating   : 1:jakarta-commons-httpclient-3.1-7.fc17.noarch             13/25

do you remember what was the old versions?

If not, I will put minimum require versions to all dependencies. This can save a lot of problems.

Here are the old and new versions of everything I updated:

apache-commons-el-1.0-22.fc15.noarch                 
                  1.0-23.fc17.noarch                 

batik-1.7-12.fc16.noarch                              
      1.8-0.1.svn1230816.fc18.noarch                 

batik-squiggle-1.7-12.fc16.noarch                    
               1.8-0.1.svn1230816.fc18.noarch        

jai-imageio-core-1.2-0.7.20100217cvs.fc17.x86_64     

lucene-2.9.4-7.fc16.noarch                            
       2.9.4-8.fc17.noarch                            

lucene-contrib-2.9.4-7.fc16.noarch                   
               2.9.4-8.fc17.noarch                   

sac-1.3-11.fc16.noarch                                
    1.3-12.fc17.noarch                                

tomcat-lib-7.0.26-1.fc16.noarch                      
           7.0.27-2.fc18.noarch                      

xml-commons-apis-1.4.01-4.fc16.noarch                
                 1.4.01-6.fc17.noarch                

tomcat-jsp-2.2-api-7.0.26-1.fc16.noarch              
                   7.0.27-2.fc18.noarch              
tomcat-servlet-3.0-api-7.0.26-1.fc16.noarch          
                       7.0.27-2.fc18.noarch          
tomcat-el-2.2-api-7.0.26-1.fc16.noarch               
                  7.0.27-2.fc18.noarch               
jakarta-commons-httpclient-1:3.1-5.fc16.noarch       
                           1:3.1-7.fc17.noarch

eclipse-4.2.0-0.11.I201204051114.fc17 has been submitted as an update for Fedora 17.
https://admin.fedoraproject.org/updates/eclipse-4.2.0-0.11.I201204051114.fc17

Package eclipse-4.2.0-0.11.I201204051114.fc17:
* should fix your issue,
* was pushed to the Fedora 17 testing repository,
* should be available at your local mirror within two days.
Update it with:
# su -c 'yum update --enablerepo=updates-testing eclipse-4.2.0-0.11.I201204051114.fc17'
as soon as you are able to, then reboot.
Please go to the following url:
https://admin.fedoraproject.org/updates/FEDORA-2012-5765/eclipse-4.2.0-0.11.I201204051114.fc17
then log in and leave karma (feedback).

eclipse-4.2.0-0.11.I201204051114.fc17 has been pushed to the Fedora 17 stable repository.  If problems still persist, please make note of it in this bug report.