DO NOT REPLY [Bug 41706] - StandardWrapper uses double-checked locking

2007-02-27 Thread bugzilla 
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--- Additional Comments From [EMAIL PROTECTED]  2007-02-27 00:48 ---
(In reply to comment #2)
 Any particular reason not to address this?

The reason is that it is extremely unlikely there will ever be a problem, and
OTOH the lock would be pretty heavily contested (so high cost, with no gain).
For example, all requests for JSPs would sync on that single lock, simply to
ensure that no request - right after the server was initialized - ever used a
second instance of the servlet (as far as I can tell).

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DO NOT REPLY [Bug 41706] - StandardWrapper uses double-checked locking

2007-02-26 Thread bugzilla 
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[EMAIL PROTECTED] changed:

   What|Removed |Added

 Status|NEW |RESOLVED
 Resolution||WONTFIX




--- Additional Comments From [EMAIL PROTECTED]  2007-02-26 10:23 ---
Thanks. This is obviously not going to be addressed, however.

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DO NOT REPLY [Bug 41706] - StandardWrapper uses double-checked locking

2007-02-26 Thread bugzilla 
DO NOT REPLY TO THIS EMAIL, BUT PLEASE POST YOUR BUG·
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http://issues.apache.org/bugzilla/show_bug.cgi?id=41706.
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--- Additional Comments From [EMAIL PROTECTED]  2007-02-26 11:56 ---
Any particular reason not to address this?

I realize that the Tomcat devs are very sensitive about performance issues, but
in this case (actually, all cases) the use of DCL doesn't guarantee correct
operation. For instance, instance could be non-null but also not initialized.

Perhaps nobody ever sees this in the wild.

I haven't had an actual problem, but noticed the use of the DCL anti-pattern
while reading the source for other reasons.


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DO NOT REPLY [Bug 41706] - StandardWrapper uses double-checked locking

2007-02-26 Thread bugzilla 
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--- Additional Comments From [EMAIL PROTECTED]  2007-02-26 12:20 ---
Oh, wait. I'm sorry.

I think that since this piece of code calls a method to instantiate and
initialize the instance member, it turns out that this is actually NOT a bug.

You can even avoid the synchronized block, since the loadServlet method itself
is synchronized, and uses only local variables.

My recommendation would be to document the code to mention DCL and why it's
still safe to do in this case, remove the synchronization within the allocate()
method, or both.

This code will be functionally the same as the existing code:
// Load and initialize our instance if necessary
if (instance == null) {
try {
if (log.isDebugEnabled())
log.debug(Allocating non-STM instance);

instance = loadServlet();
} catch (ServletException e) {
throw e;
} catch (Throwable e) {
throw new ServletException
(sm.getString(standardWrapper.allocate), e);
}
}


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