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https://issues.apache.org/jira/browse/TRINIDAD-2278?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13399384#comment-13399384
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Scott O'Bryan edited comment on TRINIDAD-2278 at 6/22/12 3:38 PM:
------------------------------------------------------------------
1) why would a lock not work? The lock ensures caching of critical sections is
release before the lock is complete, and the thread-safe nature of HttpSession
will ensure order. I'm not sure how using a Lock wouldn't work? In either
case, using a temporary object and doing a syncronize on that should work fine
also (Just be a bit slower)..
private static final Object _LOCK_OBJECT = new Object();
...
syncronized (_LOCK_OBJECT)
{
...
}
2) Trinidad versions later then 1.2 use ExternalContextUtils for this type of
information and it's coded to work with the portlet. You can do something
similar here. OR, since 1.0 is no longer maintained and the patch will be
unofficial anyway, you can probably just worry about the servlet case and let
any portal people worry about portal usecases. Trinidad 1.0 predated any known
bridge and the initial releases of the bridge built into MyFaces 1.0 and 1.1
would not run it anyway. It wasn't until the JSR-301 bridge that portal was
expressly supported and that started with Trinidad 1.2.
Just my .02..
was (Author: darkarena):
1) why would a lock not work? The lock ensures caching of critical
sections is release before the lock is complete, and the thread-safe nature of
HttpSession will ensure order. I'm not sure how using a Lock wouldn't work?
In either case, using a temporary object and doing a syncronize on that should
work fine also (Just be a bit slower)..
private static final Object _LOCK_OBJECT = new Object();
...
syncronized (_LOCK_OBJECT)
{
...
}
2) Trinidad versions later then 2.0 use ExternalContextUtils for this type of
information and it's coded to work with the portlet. You can do something
similar here. OR, since 1.0 is no longer maintained and the patch will be
unofficial anyway, you can probably just worry about the servlet case and let
any portal people worry about portal usecases. Trinidad 1.0 predated any known
bridge and the initial releases of the bridge built into MyFaces 1.0 and 1.1
would not run it anyway. It wasn't until the JSR-301 bridge that portal was
expressly supported and that started with Trinidad 1.2.
Just my .02..
> HttpSession inside a synchronized block in the class TokenCache of
> trinidad-impl-1.0.10.jar could cause to deadlock while used with WAS 7
> -----------------------------------------------------------------------------------------------------------------------------------------
>
> Key: TRINIDAD-2278
> URL: https://issues.apache.org/jira/browse/TRINIDAD-2278
> Project: MyFaces Trinidad
> Issue Type: Bug
> Affects Versions: 1.0.10-core
> Reporter: Reshmi Choudhury
>
> Hi,
> We are using trinidad-impl-1.0.10.jar in our product. I see that HttpSession
> is used in a synchronized block in the class TokenCache of
> trinidad-impl-1.0.10.jar. Could you please clarify if this could cause to
> deadlock while used with WAS 7.
> Please find the below code snippet for your quick reference.
> static public TokenCache getTokenCacheFromSession( FacesContext context,
> String cacheName, boolean createIfNeeded, int defaultSize) {
> ExternalContext external = context.getExternalContext();
> Object session = external.getSession(true);
> assert(session != null);
> TokenCache cache;
> // Synchronize on the session object to ensure that
> // we don't ever create two different caches
> synchronized (session)
> {
> cache = (TokenCache) external.getSessionMap().get(cacheName);
> if ((cache == null) && createIfNeeded)
> {
> // Seed the token cache with the session ID (if available)
> int seed = 0;
> if (_USE_SESSION_TO_SEED_ID)
> {
> if (session instanceof HttpSession)
> {
> String id = ((HttpSession) session).getId();
> if (id != null)
> seed = id.hashCode();
> }
> }
> cache = new TokenCache(defaultSize, seed);
> external.getSessionMap().put(cacheName, cache);
> }
> }
> return cache;
> }
> This information is required as IBM informs the developer not to synchronize
> the session or it will cause deadlocks. WAS 7 implements the Servlets 2.5
> specification and manages the thread safety for any modification to the
> session map. Please refer to the URL
> http://pic.dhe.ibm.com/infocenter/wasinfo/v7r0/index.jsp?topic=/com.ibm.websphere.nd.multiplatform.doc/info/ae/ae/uprs_rsession_manager.html
> for more details. This URL contains this text:
> “Applications cannot synchronize session objects inside of their servlets or
> Java Server Pages because a deadlock with the session manager may occur. The
> deadlock occurs because the session manager does not expect the use of more
> than one locking mechanism”
> Here is an excellent article on this topic, which explains when explicit
> synchronization is needed in the application code and when the servlet
> container's locking mechanism is sufficient:
> http://www.ibm.com/developerworks/library/j-jtp09238/index.html
>
> It would be really helpful if we receive the information at the earliest as
> this is priority at our end.
> Thanks in advance.
> Regards,
> Reshmi
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