The Old New Thing

April 2011 - Page 2 of 3 - The Old New Thing

Back from Las Vegas, and now my clothes smell like cigarette smoke

April 18, 2011 Apr 18, 2011 04/18/11
Raymond Chen
I actually came back Thursday night, but I've been too lazy to jot down some reactions until now. There are signs on the street directing you to a tram connecting the Monte Carlo hotel with the Bellagio. but once you follow the first sign (that takes you into the casino), there are no more signs telling you how to get to the tram. The tram ...

Don't forget to include the message queue in your lock hierarchy

April 18, 2011 Apr 18, 2011 04/18/11
Raymond Chen
In addition to the loader lock,the message queue is another resource that people oftenforget to incorporate into their lock hierarchy.If your code runs on a UI thread, then it implicitly ownsthe message queue whenever it is running,because messages cannot be dispatched to a thread untilit calls a message-retrieval functionsuch as Get&...
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Lock-free algorithms: The try/commit/(hand off) model

April 15, 2011 Apr 15, 2011 04/15/11
Raymond Chen
The last lock-free pattern for this week isn't actually lock-free,but it does run without blocking.The pattern for what I'll call try/commit/(hand off) is more complicatedthan the other patterns, so I'll start off bydescribing it in words rather than in code,because the code tends to make things more complicated.First, you take the ...
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Lock-free algorithms: The opportunistic cache

April 14, 2011 Apr 14, 2011 04/14/11
Raymond Chen
Suppose profiling reveals that a specific calculation is responsiblefor a significant portion of your CPU time,and instrumentation says that most of the time, it's just beingasked to calculate the same thing over and over.A simple one-level cache would do the trick here.Of course, this isn't thread-safe, because if one threadis pre-...
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Lock-free algorithms: Update if you can I'm feeling down

April 13, 2011 Apr 13, 2011 04/13/11
Raymond Chen
A customer was looking for advice on this synchronization problem:We have a small amount of data that we need to share amongmultiple processes.One way to protect the data is to use a spin lock.However, that has potential for deadlock if the processwhich holds the spinlock doesn't get a chance to release it.For example, it might be ...
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Overheard conversation fragment: I'm over here by the slot machines

April 12, 2011 Apr 12, 2011 04/12/11
Raymond Chen
While on a trip to Las Vegas, I happened to overhear a woman talking on her mobile phone who, from her body language, was clearly trying to meet up with a friend. We were in the casino of one of the major hotels. She said, "I'm over here by the slot machines." Yeah, that narrows it down. I'll be heading to Vegas for the Niney Awards. If I ...

Lock-free algorithms: The try/commit/(try again) pattern

April 12, 2011 Apr 12, 2011 04/12/11
Raymond Chen
The singleton constructor pattern and theInterlocked­Multiply example we saw some time agoare really special cases of the more general pattern which I'll calltry/commit/(try again).I don't know if this pattern has a real name,but that's what I'm calling it for today.The general form of this pattern goes like this:We calculate...
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Holding down the shift key when right-clicking lets you pin things to the Start menu even when you might have been better off not doing so

April 11, 2011 Apr 11, 2011 04/11/11
Raymond Chen
Holding the shift key when calling up a context menu is a convention for indicating that you want to see additional advanced options which are normally hidden. One of those options is Pin to Start menu. What is this doing as an extended command? The Pin to Start menu command normally appears on the context menu of a program or a shortcut to...